# Chevy 454 overheat



## CK82

Can anyone help!?!? I have read every forum to exist about overheating and I am still not sure what to do first in order to cure my overheating problem of my Chevy 2500 with the 7.4 liter 454. There is no problem without the plow on, everything stays right in the middle at 210 degrees. Soon as the plow is on and traveling over 40mph the temp goes up to about 240 within minutes. I have flushed the system, and removed the clutch fan spring from its slot to keep the fan engaged even at highway speeds. Removing the spring helped somewhat but the temp still sits about 240 at higher speeds. Is there any quick fix that has actually worked??? Please help, Chris


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## dj&sonplowing

454, first thing i was goning to say was fan clutch, i gotta 350 it was doing the same thing i had a after market heavy duty fan clutch put on, it solved it totally ,i try to block all the air off with plow on a warm day highest i get it is 175 now,, totall with labor was like185 not bad


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## clark lawn

is the fan shroud in good shape. also when you flushed it did you wash the outside of the rad. they get plugged up alot if you wash it use LOW pressure so not to damage the fins.


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## justme-

Well obviously the addition of the plow is the problem, and always is. Are you carrying it as low as you can, and straight to minimise the effects of air flow around it.?

Try a heavy duty service fan clutch, try a bigger radiator. Odds are you have a 2 row core and you want to look for a 4 row core. the big block puts out alot of heat so you need a big radiator.
Do you have an aux tranny cooler (besides the in radiator one)? Adding one MAY help by reducing the transmissions effect on the coolent temp, as well as an engine oil cooler may help lower engine temps.

Oh, and you do know you're really not supposed to be traveling at highway speed with a plow on right? the blade deflects alot of air and there is really little that can be done at high speed to correct it. Keep the blade straight across and as low to the ground as you can, the Rams I have noticed actually get better flow with the blade angled to one side because of the grill design.


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## CK82

The fan clutch spring is out of its slot so the fan runs non-stop, it helps some, but things are still getting way too hot. Would a heavy duty fan clutch actually help considering the fan is already running non-stop I had the radiator backflushed, not sure if it got cleaned out inside, everything works fine without the plow on, so I'm assuming its ok. I guess it could be partially plugged and its only effected when the plow is on. The fan shroud is in good shape and the fan blades are also. I am pretty sure it has an aux tranny cooler, which would be the smaller sized radiator next to the actual radiator. I'll have to check and see if its a 2 or 4 row radiator. If you guys have any more suggestions, please let me know! I would like to get this fixed without spending an arm and a leg.


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## CK82

Forgot to add, that I also have an electric fan which sits on the outer side of the radiator. I know it works, just not sure when it works or at what speeds and what not.


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## TLS

I had a 1990 454 K-3500, and know what it means to overheat with the plow on. What year is your truck? Depending on the year, is it possible it has the incorrect water pump on it? The serpentine belt equipped trucks use a different waterpump than the V-belt trucks. I've heard of many old syle pumps being installed on newer trucks making the impeller go backwards. Worked OK until the heat started.

First off, I've never heard of the fan clutch spring trick. Are you sure your getting full lockup of that viscous clutch when you do this?

You could always try a fan spacer and make the fan direct drive w/o the viscous clutch. This would only be good for winter low RPM use though.

I would get a new OEM fan clutch from GM. Make sure you specify HD, as I think there was a severe service one available for fire/amublance/tow truck etc.

Also, on the OEM aux. fan out front....I never witnessed mine come on. I wired mine to a relay that came on with the ignition. This way, it was always on. Seemed to help some. The newer 454's got better cooling in the engine. Once again, not sure what year you have.

You likely have the biggest radiator there is, but if you want to do some tweaking, you could get one for the 6.5 diesel....it's much bigger (thicker, taller, and wider). While your robbing 6.5 parts from the junkyard, grab it's bumper and shrouds, the holes in the bumper are for better cooling, and every bit will help.

I also went with a 180 degree stat....again, not sure of your year, but some computers won't do well with a colder stat.

So, anyways....what year is the truck?


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## bugthug

I have a 98 gmc with a 454. I removed the rubber gasket on the back side of the hood and I noticed about 10 degrees cooler the next time I plowed. I was toying with the idea of removing the insulation from under the hood we will see.


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## Yaz

CK82

Please add a signature with all your info, it helps us help you..

I would like to know the year, is it lifted,mods to engine, ever rebuilt, if so how much bored over, size and type of plow, size tires.

And what temp was it out side when this happens? If you put the heat on will the temp drop? by how much? If you angle, raise or lower the blade does it change temp? by how much? 

And I also have never heard of locking a clutch fan up. If you did I'm sure it will rob power and be very loud.


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## CK82

Its a '95 Silverado 2500, 454 7.4 liter. The first time removed the clutch spring from its slot the truck was really loud, but the fan did run constantly and it did help, then I replaced it after flushing the system thinking it would be ok. This didnt work so I removed it from its slot again and this time the engine didnt run as loud, each time helped the temp somewhat, but it still runs about 245 to 250. I've tried the plow down up left right, all over the place it doesnt help. Temps outside ranged from 10 degrees to 35 degrees, despite it ran hot. I think I will try some of the recommendations starting with the fan clutch. Any other info please let me know. 

Chris


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## Acmemechanic

*Hot Hot Hot*



Yaz said:


> CK82
> 
> Please add a signature with all your info, it helps us help you..
> 
> I would like to know the year, is it lifted,mods to engine, ever rebuilt, if so how much bored over, size and type of plow, size tires.
> 
> And what temp was it out side when this happens? If you put the heat on will the temp drop? by how much? If you angle, raise or lower the blade does it change temp? by how much?
> 
> And I also have never heard of locking a clutch fan up. If you did I'm sure it will rob power and be very loud.


I agree the severe duty fan clutch solved all problems on my 94 Former City Truck.They wear out and don't respond to temperature like they should.Add a blade and you actually have a Negative Airflow to the grill {Vacuum} I could be Wrong but don't believe the spring trick would work.:yow!: :yow!: :yow!:


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## Yaz

Acmemechanic said:


> I agree the severe duty fan clutch solved all problems on my 94 Former City Truck.They wear out and don't respond to temperature like they should.Add a blade and you actually have a Negative Airflow to the grill {Vacuum} I could be Wrong but don't believe the spring trick would work.:yow!: :yow!: :yow!:


CK82 If it stopped making noise it it can't be turning as fast.. I agree with Acmemechanic there is a vacuum. I would try the new fan and wiring the electric one up as well. I'm a little puzzeled as to why the electric wouldn't kick in on it own when the temp came up...


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## dj&sonplowing

id get rid of that elec fan, its probally blocking more air than doing good? if you put a hd { one made for pulling trailers} doesnt have to be chev one either, and id bet your gonnna hear them blades a singing a song, solved mine


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## TLS

The factory aux fan is about a 10" fan. It's controlled somehow to come on at certain times. I don't know what triggers it, but it's NOT the A/C. Switching mine to full on all the time helped my A/C and the Auto Trans cooler. Just wire it to a full on position and you won't hurt anything.

As for the overheating.....if you somehow were able to LOCK the fan with pulling that spring, and it didn't help your problem, then ALL our advice on replacing the clutch won't help a bit. Something is causing the overheat.

You likely do NOT have the original water pump. (certainly NOT with running full fan lockup for any period of time). I would go and check P/N's on it to make sure it's the correct one. There was a company called Stewarts who made a real good waterpump. I'd look into them. Do that, and get that radiator rodded out or replaced with a better one. I was serious about the 6.5 diesel parts, they would help, and it would make fitting a 6.5 radiator possible. Check with a good radiator shop. After 11 years, that radiator is likely shot. What temp thermostat are you running?


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## lumberjack49

Everybody is talking about the fanclutch its just my .02 cents worth are we sure that the gage is reading right is it the factory gage that you are relying on or an aftermarket one


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## justme-

What about that t-stat? how old is it? They do fail, and they do start failing long before the completely fail- if it's the original stat change it.

I would not remove the elec fan- they never block more than they pass- often guys drop the mechanical fan and replace it with a pair of electrics one on each side.

You probabily have the biggest radiator they offered, but that doesn't mean it's a 4 row core. you said it runs 210 w/o plow, that's winter temp- how hot in the summer? IMO 210 is too hot anyway- should be under 200.
It is possible the guage is going, but not likely.


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## douglasl330

I'm with TLS if you can find a used diesel radiator cheep throw it in! We are all forgetting that the temp sensor is on the engine and not the radiator! Can you tell when the t-stat opens--you will see the gauge drop down when cooler coolant enters the engine! If this is what you are seeing and you use the truck just for plowing this time of year--you may just want to yank the t-stat and fab a restrictor plate for plowing. The truck will suffer when cold(sluggish), but won't see the high temps. your cab heat won't be so hot! It takes about 5-minutes to swap out so you could do this when putting the blade on!--This is just an alternative and not a fix to your problem! Is there any chance that the bypass hole for the waterpump is restricted? This would cause the truck to run hot, then adding the blade sends it to 240. You do need to make up the air flow if that is the only time that you see the overheat problem! Hd fan and maybe an additional switched electric fan!

Think Snow!


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## KingDuramax

justme- said:


> you said it runs 210 w/o plow, that's winter temp- how hot in the summer? IMO 210 is too hot anyway- should be under 200.
> It is possible the guage is going, but not likely.


I had a 95 1ton Dually with the 454. Even in the summer pulling the racecar trailer(32foot gooseneck) I wouldnt get that hot. Sounds like you need to look into it a little further. One thing noone has mentioned... 
Is the coolant level full??
Change the T-stat thier cheap
Make sure the clutch fan is working properly 
Make sure the electric fan is kicking on when it gets hot, Not sure what temp that is. Call your Chevy dealer and ask them. 
If this dosen't help it. You could always build a custom air dam to direct air up to the radiator from the bottom.
Hope this helps.


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## CK82

The truck runs at 210 which is directly in the middle all year round, the only problem comes when the plow is on. Is that too hot for a 454 to run? The coolant is full and has been backflushed recently. If 210 is hotter than normal, then I have a different problem, as it is running hot without the plow on then. I just assumed that 210 was where it should be at. The electric fan works, I see and hear it on when I first start up the truck, I'm not sure when it comes on after that and am curious to find out? I feel thats odd that the electric fan runs when the truck first starts up, but thats just me. The radiator and t stat are factory and then over 10 years old from what I know, I think getting the rad. rodded or boiled or whatever they do would help. The truck will heat up somewhat quickly at 20 degrees outside temp and will go right to 210 and hover there, it seems the longer I drive without stopping and the warmer the fluids get, trans, oil, etc thats when the temps rise up to 240 or so. Is the t-stat failing if it keeps the engine from overheating (210) during normal driving? I think I'll start with the rodding/boiling of the radiator, then the fan clutch. I would just like to not have to try every suggestion in order to get this solved, even though I know its trial and error somewhat.

Chris


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## TLS

You still haven't mentioned the water pump. When your doing all this, if it IS still original, REPLACE IT! Either get a new GM or a Stewart's as they know how to rebuild them right. Plus their under $100 shipped. Make sure you replace the bypass hose too. 









Also....

If thats the original radiator, you'd likely benefit from a new one.

So.....
New HD clutch fan.

New waterpump.

New T-Stat

New hoses/gaskets

New or Rebuilt radiator

New coolant

And you should be all set.


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## CK82

TLS would you recommend doing all of these things at once, or starting with say the water pump and radiator rodding or replacement? I sure would hope replacing that many things would take care of my problem, from what it sounds thats what it is going to take. By the way thanks for your advise.

Chris


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## TLS

I would recommend most of them. As most of these parts coincide with others. While you have the radiator out, the coolant will be drained. Perfect time for the waterpump and clutch fan. Hoses are just common sense at that point too. And with it all drained, a T-Stat is a no brainer. Use a good GM or equivilent T-stat gasket, the ones with the silicone impregnated seal around them.

At 10+ years old, most of these items are on borrowed time anyways.


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## topdog

i have a 94 chevy 2500 454, and when i got my western plow installed did the exact same thing. i replaced the electric fan on the front of the radiator with a new gm one, and has worked great. even driving down the highway with plow on now it doesn't get that hot. that is what worked for mine anyways. we noticed it wasn't kicking on as much as it should, but seems to work great so far....even for our one push all season =(


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## CK82

Top Dog:
So you replaced the electric fan, was it faulty, or did you add a bigger one in place of the old one, give me some information, it might help. My electric fan on the front of the radiator works at start up I know for sure.

TLS:
I will take your advice also, THANKS.

Chris


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## topdog

i think it wasn't working up to speed it would kick on, but it didn't seem like it was turning fast enough. i bought the gm fan for it...( couldn't find a non dealer part) one place wanted $90 for it (chevy dealership) got it for around $70 (gm dealership). did notice the fan was spinning faster once i put the new one on. sucks cause you have to pull off the whole front grill to install it, but has worked for my truck.
i have a 94 2500 chevy extended cab 8 ft. bed with about 140k miles on it with a trany cooler.
my plow is a 2005 western 8ft. ultra mount with wings, back drag, and snow deflector.
also installed timbrens on the front last week.


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## justme-

douglasl330 said:


> We are all forgetting that the temp sensor is on the engine and not the radiator! Can you tell when the t-stat opens--you will see the gauge drop down when cooler coolant enters the engine! If this is what you are seeing and you use the truck just for plowing this time of year--you may just want to yank the t-stat and fab a restrictor plate for plowing. The truck will suffer when cold(sluggish), but won't see the high temps.


No, I think we all know the temp sensor is on the engineblock- and I think you're applying diesel cooling systems to a gasser. Remember the sensor is usually on the back and top of the block, at the hottest point of the engine.

NEVER remove the tstat unless you know exactly what you're doing.

The proper tstat will open when the engine reaches a set temp and stay open allowing the radiator to work- it should NOT cycle as diesel's do. A gas engine temp guage should be stable- they work best at a stable temperature, and the computer systems like it alot more than having to constantly adjust to engine temp. If an engine is run ice cold, say without a t-stat, the block will not heat up properly, the computer will throw a fault code, and the engine will tend to carbon. The combustion chamber needs to reach a certain temp to properly burn the ful. If it doesn't it will run poorly, produce extra emmisions (throwing possibly several fault codes), carbon the chamber, includeing the spark plugs, and can carbon the o2 sensors, and the injectors.

Diesel's often cycle the temps- my 96 Ram has a 180* tstat- under high work conditions before I had the colling system done (last week my t-stat started sticking, first closed then open) I would max at 210 before the stat opened and the radiator dropped it back to 170, normally it runs from 150 to 180. So yeah, 210 is a bit high IMO. Diesel's cycle because the radiator is so big under normal conditions the engine would be running cold with a gasser type stat. When my stat stuck open at idle the temp dropped from 180 to not registering (under 120) in under 2 minutes!

While you have the cooling system open is the time to replace everything related that you can. I had planned on changing the coolent this past fall and noticed a hard line rusted bad- spent 2 weeks figuring out what line it was (from Dodge and Cummins), bought the wrong line, figured out what it was and decided to buy and change all the steel coolent lines. Since the system was going to be open I planned on changing the coolent, t-stat and all hard lines- everything except the pump. When the tstat stuck it became emergency- so I had my mechanic do it- all of it. No sense changing the stat and adding back old used coolent, then changing the rotted line in the spring, then another....


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## TLS

justme- said:


> No, I think we all know the temp sensor is on the engineblock- and I think you're applying diesel cooling systems to a gasser. Remember the sensor is usually on the back and top of the block, at the hottest point of the engine.
> 
> NEVER remove the tstat unless you know exactly what you're doing.
> 
> The proper tstat will open when the engine reaches a set temp and stay open allowing the radiator to work- it should NOT cycle as diesel's do. A gas engine temp guage should be stable- they work best at a stable temperature, and the computer systems like it alot more than having to constantly adjust to engine temp. If an engine is run ice cold, say without a t-stat, the block will not heat up properly, the computer will throw a fault code, and the engine will tend to carbon. The combustion chamber needs to reach a certain temp to properly burn the ful. If it doesn't it will run poorly, produce extra emmisions (throwing possibly several fault codes), carbon the chamber, includeing the spark plugs, and can carbon the o2 sensors, and the injectors.
> 
> Diesel's often cycle the temps- my 96 Ram has a 180* tstat- under high work conditions before I had the colling system done (last week my t-stat started sticking, first closed then open) I would max at 210 before the stat opened and the radiator dropped it back to 170, normally it runs from 150 to 180. So yeah, 210 is a bit high IMO. Diesel's cycle because the radiator is so big under normal conditions the engine would be running cold with a gasser type stat. When my stat stuck open at idle the temp dropped from 180 to not registering (under 120) in under 2 minutes!


SUMMARY: Make sure you run a thermostat. 

Personally I like to run Robertshaw's, as they are a bit more accurate and open WITH the flow of water, not against. They're double the price of cheapo's, but at only $6, double isn't all that much!

As for the electric fan...The factory GM aux. fan really isn't a great performer to begin with. Somehow you need to figure out WHEN the computer is calling for it to come on. What temp/conditions. Mine NEVER spun at startup. Sure, it spun, but that was because the BIG clutch fan was drawing so much air, it spun the electric one with just the air movement.

Do what I said, and get a nice relay or solenoid and wire that fan up direct. Wire it to a switch if you'd like. This way when plowing you can flick it on. While sitting in traffic in the summer, just flick it on. But if you put 12V to it and it spins and doesn't make any funny bearing noise, you should be set!

But like I said....definately get the new radiator (or get a good radiator shop to rebuild yours).

May sound silly, but make sure you use 50-50 mix of coolant. I've seen many a guy use straight coolant and overheat/freeze up. Ethylene Glycol NEEDS water to work. By itself it will freeze and boil.


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## CK82

Ok looks like I have some work to do, I think I'll start with at the radiator and wiring the aux. electric fan up to a switch, I'll check into prices for the other things and from what it sounds replace them while the radiator is out. Thanks for all your help guys.

Chris


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## KingDuramax

CK82 said:


> Ok looks like I have some work to do, I think I'll start with at the radiator and wiring the aux. electric fan up to a switch,
> Chris


I wouldn't do that. If GM wanted it on a switch it would be on one. Leave it the way it is. Just make sure it is working properly. What if someone borrows the truck and dosen't turn on the switch now you need a motor!!! Think about it. Obviously we can all tell you replace this replace that. If you cant diagnose it yourself take it to the dealer who works on these trucks all day long and have it fixed right. You are getting too many opinions thrown at you.
Good luck


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## TLS

Just remember, these trucks overheated from the factory. Going to GM for a problem they couldn't fix in 1995 wouldn't be my first choice.

The aux. electric fan was a band-aid afterthought to begin with. It comes on too late to do any good. Don't like the switch idea, wire it direct.

This advice I'm giving you is from PERSONAL experience with a truck with the same engine. A truck that gave me grief with this EXACT problem.


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## CK82

TLS:

Another quick question, since the temp gauge sits at 210 during normal operation at all temperatures, wouldnt you think the radiator is still working. I spoke with a radiator shop/guy today and he said something about the radiator that my truck has is aluminum or something and can't be rodded out? Instead he said he can check it to see if it needs to be cleaned (not sure if that means boiled). Man I really would like to get this fixed with a realatively low cost. Not $520 to pull and replace the radiator as he quoted me. I just dont understand why the temperature decides to always sit at around 210, he also said replacing the t-stat with a lower temp one say 185 ISN'T a good idea. Sorry to beat this subject to death, I dont know as much as I probably should about repairs. Thanks for baring with me.


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## topdog

let me know what you do to fis the prop. just curious if it will be the same as mine. if you want to go cheap try replacing the thermastat first not expensive and can do it your self.


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## TLS

I forgot what year they went to aluminum radiators, somewhere between 1990 and 1995 I guess!

You should be able to get a good aftermarket radiator. Check this forum out it deals with '90-'93 BBC's.

If you don't have the mechanical ability to tackle this yourself, you're likely going to have to shell out some cash to get this straightened out.

The issue with the 180 stat is that the fan clutch is calibrated for 195. With a 180 stat, the coolant flows to the radiator, but there isn't immediate fan engagement as it's still too cool to trigger it's lockup.

Stick with a 195 stat. Actually, if your trying to take care of this on the cheap.......do the stat (195 Robershaw) and a new HD fan clutch first. Both aren't going to be all that much money, and with simple hand tools, can be done in a couple of hours.

The radiator _should_ still be considered for replacement sometime soon if you plan to keep the truck. At that time, replace the water pump and hoses.

I'll try to look in my electrical wiring manual for my old '90 to see if I can determine what triggers the aux. electric fan. Hooking that up hot all the time cant hurt though.


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## CK82

I'm going to start with the T-stat when I have the radiator looked at tomorrow, and then I'll go from there if the problem isnt fixed I will upgrade to a HD fan clutch. Thanks for you help guys. TLS let me know if you find out anything about the aux. fan and when it runs.

Chris


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## topdog

good luck hopefully it will be simple like mine was


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## justme-

I would never go to a GM dealer for this kind of issue- unless they are a BIG truck only shop. Even with the best intentions 90% of the service techs at a dealership are book smart, not experiance smart and GM has a reputation for the engineers being wrong in design and build phases so the techs have no experiance to fall back on. Remember the alignment problems for the 1980-1987 K series trucks? Engineering failures at work.(GM never did issue a correction or recognise the problem... tells you why they're having bankruptcy issues, huh)


If you can, have the radiator rebuilt, and a copper core will be cheaper- porbabily better. I'm not aware of any other manufacturer useing aluminum for truck radiator cores... probabily says something there too.

There's several of us throwing info, but we're all saying the same things....


TLS- thanks for the summary. :>


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## RJ snow

CK82 said:


> Forgot to add, that I also have an electric fan which sits on the outer side of the radiator. I know it works, just not sure when it works or at what speeds and what not.


CK has the right answer to your problem. And as a matter of fact you can get a electric fan that is temp controlled so when you have your plow on it will run when it reaches normal operating temp. Some can be set to go on at whatever temp you want so that you could make it run at 220F and it will cool till it hits 210F and shut off there by not wasting battery power and keeping your engine at the proper temp. Your problem is obviously lack of air flow through the grill/radiator. Also while the plow is off the fan won't run unless you get to the higher setting. Also comes in handy in summer with AC on.


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## RJ snow

CK82 said:


> Can anyone help!?!? I have read every forum to exist about overheating and I am still not sure what to do first in order to cure my overheating problem of my Chevy 2500 with the 7.4 liter 454. There is no problem without the plow on, everything stays right in the middle at 210 degrees. Soon as the plow is on and traveling over 40mph the temp goes up to about 240 within minutes. I have flushed the system, and removed the clutch fan spring from its slot to keep the fan engaged even at highway speeds. Removing the spring helped somewhat but the temp still sits about 240 at higher speeds. Is there any quick fix that has actually worked??? Please help, Chris


CK theres nothing wrong with your truck... Go get an after market electric cooling fan with adjustable temp controls. set it to turn on at 225 and turn off at 210 this will keep your temp where it should be without using much battery power and also with the plow of won't effect running temp at all. The problem is that your plow is blocking the ram air effect through your grill. Adding a HD clutch fan may help slightly but won't fix it. An additional fan pushing air through the rad from outside ambient temp will fix it. I have used this fix many time over the years at a number of Chevy Dealerships where I worked with HD Trucks Deisel & Gas. Save your self alot of money and skip to adding the electric fan. If your truck was equipped with an aux fan I'd be checking fuses ect and at least hot wire it to see if it actually works at all. Some HD/Plow packages include these fans just for the reason that theres no Ram air with a plow on. Also I wanted to add that if your truck is AC equipped this will exaggerate the problem cause air has to be pulled through the condensor too. Best way to go is after market High Flow Elec Fan with temp control. 
If you replace your t-stat to a lower temp you'll notice poorer gas mileage and performance. These newer trucks run hot cause they have to so that they can burn the sh## gas we have nowdays. If the truck only does this when the plow is on then you probably don't have a problem with your cooling system unless the aux fan is malfunctioning in which case the After market fan would be a better solution anyways.


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## brad96z28

There is not wrong with ur truck! Ive also has sililar problem on a few of my trucks highway driving only! The plow diverts the cool air over ther trucks hood. Generaly fan clutch and electric fan is only gona be pushing around hot air. with the plow on and at crusing speed.The bigest thing that will help is the bigest radiator u can put in it and alot of the trucks came with the standard 2 row radiator! Put in a 4 row and make sure it is a quality radiator like a visteion not a spi or a ready rad please do urself a favor and ck to see if u have a 2 row radiator. Obvoiusly if the truck is fine in summer and winter and it only acts up with the plow on it the cooling system is not big enough.If u buy a late model chevy truck with snow plow prep it has a heavier duty cooling system for this problem. My last 2 trucks did this same thing til i got my diesel that holds 26 quarts of coolant. Ur watter pump and thermostat sound fine! But It is always a good idear to change ur t stat if u work on the cooling system and buy a superstat thata the best t stat to get.


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## brad96z28

brad96z28 said:


> There is not wrong with ur truck! Ive also has sililar problem on a few of my trucks highway driving only! The plow diverts the cool air over ther trucks hood. Generaly fan clutch and electric fan is only gona be pushing around hot air. with the plow on and at crusing speed.The bigest thing that will help is the bigest radiator u can put in it and alot of the trucks came with the standard 2 row radiator! Put in a 4 row and make sure it is a quality radiator like a visteion not a spi or a ready rad please do urself a favor and ck to see if u have a 2 row radiator. Obvoiusly if the truck is fine in summer and winter and it only acts up with the plow on it the cooling system is not big enough.If u buy a late model chevy truck with snow plow prep it has a heavier duty cooling system for this problem. My last 2 trucks did this same thing til i got my diesel that holds 26 quarts of coolant. Ur watter pump and thermostat sound fine! But It is always a good idear to change ur t stat if u work on the cooling system and buy a superstat thata the best t stat to get.


If u need any wiring diagrams on that electric fan system to see if it is working propperly let me know. Let me know. [email protected]:waving:


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## brad96z28

brad96z28 said:


> If u need any wiring diagrams on that electric fan system to see if it is working propperly let me know. Let me know. [email protected]:waving:


 Oh just wanted to let u know one more thing In the 8 years that I have been a full time tech I have seen 1 watter pump that caused a cooling system problem!!!!!!!!!!!!!!!!!!!!!!! Count em 1. They either leak or the bearing goes bad and they make noise very very very rarely can it cause a cooling system problem.I belive on the 454 pump it has a cast impeller and not much can happen to it.


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## RJ snow

brad96z28 said:


> There is not wrong with ur truck! Ive also has sililar problem on a few of my trucks highway driving only! The plow diverts the cool air over ther trucks hood. Generaly fan clutch and electric fan is only gona be pushing around hot air. with the plow on and at crusing speed.The bigest thing that will help is the bigest radiator u can put in it and alot of the trucks came with the standard 2 row radiator! Put in a 4 row and make sure it is a quality radiator like a visteion not a spi or a ready rad please do urself a favor and ck to see if u have a 2 row radiator. Obvoiusly if the truck is fine in summer and winter and it only acts up with the plow on it the cooling system is not big enough.If u buy a late model chevy truck with snow plow prep it has a heavier duty cooling system for this problem. My last 2 trucks did this same thing til i got my diesel that holds 26 quarts of coolant. Ur watter pump and thermostat sound fine! But It is always a good idear to change ur t stat if u work on the cooling system and buy a superstat thata the best t stat to get.


 as far as t-stats and cooling flush and 2 core radiator and some of the others... no. I'd say the problem is definetly no ram air through the grille/rad. and if it's equipped with a aux fan that is what the problem is. As far as the aux fan where is the warm air coming from ? Its a push fan not a pull fan the clutch fan pulls air through and the elec fan pushes it through. there is no hot air outside the truck in front of the condensor/radiator now is there. The HD/Plow packages include these fans for that reason from the factory. The aftermarket solution will be better cause you can get a higher flowing fan thats customizable temperture wise for your application.

http://www.partsamerica.com/ProductDetail.aspx?categorycode=6003&mfrcode=PRF&mfrpartnumber=67010

http://www.partsamerica.com/ProductDetail.aspx?categorycode=6003&mfrcode=PAI&mfrpartnumber=30104

Have a look at these links at Parts America


----------



## RJ snow

brad96z28 said:


> Oh just wanted to let u know one more thing In the 8 years that I have been a full time tech I have seen 1 watter pump that caused a cooling system problem!!!!!!!!!!!!!!!!!!!!!!! Count em 1. They either leak or the bearing goes bad and they make noise very very very rarely can it cause a cooling system problem.I belive on the 454 pump it has a cast impeller and not much can happen to it.


The 15 years as a Tech and the last 7 or 8 as an Engineering Tech I would say I have to agree with ya.....


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## RJ snow

Just as a note I've also never seen a truck with a plow on it being tested in the wind tunnels at GM for cooling system optimization either.

These trucks nowadays are being designed to haul weight and get good fuel economy as well as the yuppie comfort riding standards. Trucks of years past didn't have alot of these problems cause the grills were wide open, and 25-35 years ago trucks with AC standard was un heard of. The whinners that want all the luxury along with the workability are sending these things into a world of problems. That why 35 years ago you could buy a nice HD truck for much less than a nice car, nowdays its reverse and getting worse.


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## TLS

RJ and Brad,

Thanks for all your info and suggestions.

Unfortunately, some are not entirely correct.

The auxillary fan that he has is either temp or computer controlled. The temps that it is told to engage is entirely TOO high.

He has a 195 degree T-stat. Truck _should_ run @ that temp...maybe 200.

Adding a cooler T-stat WILL produce MORE power, not less. Not that it matters here, but just getting this out there because saying it will make less power is just incorrect.

At 10+ years old, to replace a clutch fan, and a radiator is just smart thinking, as they're at their expected life to begin with. And with an unknown maintenance history, perhaps beyond their life. While doing this, new hoses and a water pump is simply a smart idea. Especially if he was running his current clutch fan at 100% lockup for an extended peroid of time. (I went through 2 waterpumps and 2 radiators in 15 years on my similar truck)

Yes, his problem IS air-flow through the radiator (snowplow related). Making sure this aux cooling fan comes on prior to 250 degrees is very important. Important for triggering the temp coil on the clutch fan.

One good thing RJsnow eluded to is the adjustable fan thermostat. With GM's temp control of this fan being a mystery, simply adding an adjustable fan thermostat to it is a pretty good idea. I'd set it in the 200on 190off zone. This will ensure it will stay on at operating temp forcing air across your clutch fan.

I still feel though Chris, that you need to eventually do all of my suggestions. Especially if you plan to keep this truck. You will not only eliminate your overheating problem, but also prevent other future problems as well.

So as a recap in order of importance:

NOW
* New HD GM clutch fan
* Hotwire or fan control relay the aux. fan
-----------------------------------------
LATER
* New 195 T-stat
* New radiator
* New Hoses
* New waterpump
* New 50/50 coolant


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## justme-

I guess you two techs have been lucky- I have seen a few GM water pumps with impellers rusted severe enough to reduce effeciency. the majority of the problems are leaking seals- but I have replaced 2 on my family's vehicles that were impeller related problems.

And TLS is right on the tstat temp - if you have a 195* stat it opens when the coolent at the stat is at the opening temp- 195*. the temp guage in the dash will read a little (just a little if the system is properly operating) higher, as in maybe 3 degrees higher because the tstat is in the FRONt of the engine block and the sending unit is in the rear at the top in most blocks- the hottest point.
In gas engines the stat should open and pretty much stay open keeping a consistant temp with coolent circulating through the radiator all the time once it's up to the correct temp. Stats wear out and should be changed regularly just like coolent- they do loose their setting through age. The wax pellet capsule can leak in coolent changing the opening temp, the spring can weaken or work harden again changing the operating temps. This paragraph should be almost standard in every ASE cert class, it's in almost every manufacturer's factory service manual.....


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## brad96z28

justme- said:


> I guess you two techs have been lucky- I have seen a few GM water pumps with impellers rusted severe enough to reduce effeciency. the majority of the problems are leaking seals- but I have replaced 2 on my family's vehicles that were impeller related problems.
> 
> And TLS is right on the tstat temp - if you have a 195* stat it opens when the coolent at the stat is at the opening temp- 195*. the temp guage in the dash will read a little (just a little if the system is properly operating) higher, as in maybe 3 degrees higher because the tstat is in the FRONt of the engine block and the sending unit is in the rear at the top in most blocks- the hottest point.
> In gas engines the stat should open and pretty much stay open keeping a consistant temp with coolent circulating through the radiator all the time once it's up to the correct temp. Stats wear out and should be changed regularly just like coolent- they do loose their setting through age. The wax pellet capsule can leak in coolent changing the opening temp, the spring can weaken or work harden again changing the operating temps. This paragraph should be almost standard in every ASE cert class, it's in almost every manufacturer's factory service manual.....


Just because u have a 195 t stat doesnt mean that it should always run at 195 or close to it. If it has an electric fan it the temp is gona change fairly well, no way is the temp gona be constant. If that where the case there would be no need for electric fans. When a car sits at idle for a long period of time the temp can vary by 20 degrees the car is gona run to when the fan is programmed at not when the thermostat opens. say most gm cars have 195 stat fan on at example 222 off at 210. The car is gona run at these temps regaurdless of the t stat.And driving down the road it may be running 195- 200


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## brad96z28

RJ snow said:


> as far as t-stats and cooling flush and 2 core radiator and some of the others... no. I'd say the problem is definetly no ram air through the grille/rad. and if it's equipped with a aux fan that is what the problem is. As far as the aux fan where is the warm air coming from ? Its a push fan not a pull fan the clutch fan pulls air through and the elec fan pushes it through. there is no hot air outside the truck in front of the condensor/radiator now is there. The HD/Plow packages include these fans for that reason from the factory. The aftermarket solution will be better cause you can get a higher flowing fan thats customizable temperture wise for your application.
> 
> http://www.partsamerica.com/ProductDetail.aspx?categorycode=6003&mfrcode=PRF&mfrpartnumber=67010
> 
> http://www.partsamerica.com/ProductDetail.aspx?categorycode=6003&mfrcode=PAI&mfrpartnumber=30104
> 
> Lol If it could get cool air from outside the truck we would not be having this conversation


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## brad96z28

We all agree that the problem is the plow being on the truck. But what will help the situation? If the aux fan is not working at all, then fixing that fan, or an replacing it with aftermarket fan may will do the job. But seeing how it doesnt have a problem in summer I bet it works. What will help Is a bigger radiator. It may not solve the problem but it may take a lot longer for it to heat up while driving. Answer me this guys if both fans work why dont they work when he has the plow on driving? Because it cannot pull in the cool outside air rite? Id like to know when the truck gets hot say over 230 and u open the hood is that aux fan running? Have u seen that fan run? Good luck


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## brad96z28

Belive it or not I had saved the 1 watter pump that I have ever seen cause a cooling Issue. Makes a good conversation piece cause it is such a rare occorance Here is a picture of it. My boss has run his garage for 33 years and this is the first one he has seen cause a cooling issue. Oh by the way This was a replacement watter pump that was less then a year old.


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## brad96z28

Has anyone seen my fins???????????????


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## Acmemechanic

*Disolved Impellers*



brad96z28 said:


> Belive it or not I had saved the 1 watter pump that I have ever seen cause a cooling Issue. Makes a good conversation piece cause it is such a rare occorance Here is a picture of it. My boss has run his garage for 33 years and this is the first one he has seen cause a cooling issue. Oh by the way This was a replacement watter pump that was less then a year old.


I will agree it is a rare Occurence Disolved impellers that is but I have seen about 5 I believe in my 25 years and each time It was found as a last resort diagnosis.I believe that you guys advising That a 50+/- Dollar part be overlooked are doing the Poster a Disservice.If he/she does their own work than changing it Will Add to their Vehicles Dependabity factor at best.I am suprised no Ford Techs got in and advised Knocking all the Freeze out plugs out and Pressurewash the cooling jacket.Do not Attempt this at home!!!Or on anything other than a Ford!!!:yow!: :yow!: :yow!:


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## Acmemechanic

Acmemechanic said:


> I agree the severe duty fan clutch solved all problems on my 94 Former City Truck.They wear out and don't respond to temperature like they should.Add a blade and you actually have a Negative Airflow to the grill {Vacuum} I could be Wrong but don't believe the spring trick would work.:yow!: :yow!: :yow!:


I state again NEGATIVE AIRFLOW is the Heart of the problem


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## RJ snow

brad96z28 said:


> RJ snow said:
> 
> 
> 
> as far as t-stats and cooling flush and 2 core radiator and some of the others... no. I'd say the problem is definetly no ram air through the grille/rad. and if it's equipped with a aux fan that is what the problem is. As far as the aux fan where is the warm air coming from ? Its a push fan not a pull fan the clutch fan pulls air through and the elec fan pushes it through. there is no hot air outside the truck in front of the condensor/radiator now is there. The HD/Plow packages include these fans for that reason from the factory. The aftermarket solution will be better cause you can get a higher flowing fan thats customizable temperture wise for your application.
> 
> http://www.partsamerica.com/ProductDetail.aspx?categorycode=6003&mfrcode=PRF&mfrpartnumber=67010
> 
> http://www.partsamerica.com/ProductDetail.aspx?categorycode=6003&mfrcode=PAI&mfrpartnumber=30104
> 
> Lol If it could get cool air from outside the truck we would not be having this conversation
> 
> 
> 
> Not for nothin Brad but where is heated air coming from in front of the core support or in front of the radiator. The problem is flow through. Even if the air in front of the rad is 10F, if there is not enough flow it won't cool at its optimal level which is what CK is experienceing. Don't laugh to loud....
> 
> An electric fan will pull ambient air from from behind the plow which maybe whatever temp it is outside and froce it through the rad at whatever CFM its rated for therefore increasing cooling capacity to remedy a hot running truck with a plow on it.
> As far as lower temp making more power is not actually correct it will decrease fuel economy because your fuel mixture will be richer via the ECM which thinks motor is colder than it should be. Todays gas needs an op temp to be in the 200-220 range for optimal burn in the cylinder.(The lower the Octane the Higher the burn temp needed) And with todays prices at the pump I'd bet he's been using 87Octane like most everyone else.. Also there's one thing nobody here has mentioned... the radiator cap...Remember that 210F under 16# pressure is actually quite a bit higher temp than what you actually relize. Especially since your combustion chamber temps are running near 1280F.
Click to expand...


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## RJ snow

CK my reccomendation is to totrally rebuild your entire cooling system...After that if you still have a problem then go back to my original post reply and install the High flow electric fan. ROTFL 

Seriously... If you jump in and replace the water pump on an old system the next thing to go will be your Rad or heater core. (Just because of increased pressure and flow in the system.) And beleive me you don't wanna be changin out a heater core with snow on the way or in lousy weather.
As always, if your replacing temp related components on your engine it is a wise practise to replace the T-stat too.
A much forgoten item is your Rad cap, if it doesn't hold a proper pressure the temps will rise dramaticlly while at higher speeds and higher power situations.

While I think most of our intentions here are good, My choice would be to correct a root problem therefore saving you a bunch of money and time.

The best practise is to look for the obvious and check the rest. 
If the waterpump is not leaking or making noise don't touch it. 
Would you replace your radiator just for the hell of it(point taken?)
The obvious would be you put on a plow.
Take the plow off and put a piece of cardboard in front of your radiator it'll probably do the same thing as when the plow was on...(air flow problem)
Generally if the aux fan came from the factory it will be hooked up to an independant coolant temp sensor.(it may be broken or corroded connections)
Find that sensor and jump it to turn on your fan.
The aux sensor will also be set for a higher temp than a ECM sensor but less than the dummy light sensor. Your GM dealer will know what that temp is and should have that part in stock. Most chiltons manuals have component locations if you don't know where to look for it. 
Generally speaking the ECM sensor will have 2 wires and a very small connector with 28or36 gauge wire. The fan sensor usually has 1 wire connector as well as a dummy light sensor with 16 or 24 gauge wire(thicker).(if i'm not mistaken its a dark green wire)
Pop off the connector from the sensor and short it to ground and the fan should run. The coolant sensors control ground. The ECM sensors are variable resistance which gives the ECM a variable voltage signal.(1-5 vdc) hense the 2 wires, one is 5vdc signal and the other is variable vdc return. I could really go into it as far as how to diagnose this but I want to get some rest before the storm gets here tonight. 
Trust me get the electric fan workin/replaced and your problem will be solved.


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## brad96z28

Acmemechanic said:


> I will agree it is a rare Occurence Disolved impellers that is but I have seen about 5 I believe in my 25 years and each time It was found as a last resort diagnosis.I believe that you guys advising That a 50+/- Dollar part be overlooked are doing the Poster a Disservice.If he/she does their own work than changing it Will Add to their Vehicles Dependabity factor at best.I am suprised no Ford Techs got in and advised Knocking all the Freeze out plugs out and Pressurewash the cooling jacket.Do not Attempt this at home!!!Or on anything other than a Ford!!!:yow!: :yow!: :yow!:


 Well most of are trying to figure out what the real problem is before we throw around 50 bucks or whatever on something that is a shot in the dark to say the least. Some basic testing of that fan is the key at this point, and then take it from there.Once he gets the truck in proper working order he can worry about dependability.A disservice would be a waste of 50 bucks when u indeed have a bad fan motor!


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## brad96z28

brad96z28 said:


> Well most of are trying to figure out what the real problem is before we throw around 50 bucks or whatever on something that is a shot in the dark to say the least. Some basic testing of that fan is the key at this point, and then take it from there.Once he gets the truck in proper working order he can worry about dependability.A disservice would be a waste of 50 bucks when u indeed have a bad fan motor!


ck did u get any wiring info yet on that fan motor?


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## RJ snow

CK how did ya make out with the cooling problem ? 
I wanted to post this for ya so you have a tried and true procedure...

coolant temp sensor is located = UNDER HOOD, CENTER, UPPER ENGINE AREA, PASSENGER SIDE OF WATER OUTLET, MOUNTED IN INTAKE MANIFOLD

*cooling fan switch is located = UNDER HOOD, PASSENGER SIDE, LOWER ENGINE AREA, ABOVE CENTER EXHAUST PORTS, MOUNTED IN CYLINDER HEAD*

coolant needed for 50/50 mixture is =ANTIFREEZE NEEDED 3 5/8 GALLONS FOR A 50/50 MIX

*OPERATION* 
The auxiliary fan circuit contains the auxiliary fan, coolant temperature sensor and a relay. When the sensor reaches a predetermined temperature, it closes the circuit to the relay. This energizes the relay sending 12 volts to the auxiliary fan. When the temperature decreases below the set point of the sensor, the circuit opens and the voltage is no longer applied to the auxiliary fan. 
*TESTING *
1 Check the condition of the fan switch and wiring. Repair as necessary. 
2 Attach one end of a jumper wire to a good 12 volt power source and the other end of the jumper wire to the orange wire at the cooling fan relay. 
3 The fan should operate. If the fan does operate the switch is probably defective. 
4 If the fan does not operate, unplug the fan electrical harness and apply 12 volts directly to the fan. If the fan does not operate, the fan motor is probably defective. If the fan does operate, the relay could be defective. 
*REMOVAL & INSTALLATION* 
1 Disconnect the negative battery cable. 
2 Disconnect the sensor electrical lead and unscrew the sensor. The sensor can be found on the right side of the engine.



















I'm certain this will answer any fan related questions so get out your test light and/or DVM and make sure whats working and not working before ya spend a fortune chasing a problem


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## TLS

Any of you other guys here actually HAVE this same truck with this problem?

Mine overheated in the Summer when towing. Where's the plow blocking airflow problem there? Going down the highway.....where's the electric fan there? It was running, remember. These trucks ran hot. And were on a fine line when they left the factory.

Yes, it is an airflow problem. Replacing his clutch fan and T-stat is likely all he needs to do. Hot wiring the aux. electric fan to either a switch, a temp switch, or hot all the time will help, but NOT be a cure all. It's a low rpm 10" shroudless AUXILLARY fan. Have you guys actually SEEN this aux. fan? With all that fancy wiring and what not, the fact is, this tiny fan is only good for creating a slight breeze which may help activate the thermo coil on the clutch fan.

His problem is the age of everything guys. It's a 10+ year old truck. My similar/exact truck started having problems well before that age.

When I mentioned the water pump, I NEVER indicated that it was the *cause* of his problem. For a BBC water pump to last 10 years is stretching it. However, replacing a clutch fan that was rigged to stay locked up all the time, and draining coolant to replace T-stat and radiator, your freakin ******** not to put a new water pump on it WHILE all of this is off. Hell, if it had a ton of miles on it, I'd say to throw a timing chain on it as well! You guys are thinking like mechanics, I'm thinking logically.

If he plans to keep this truck, ALL of these things will NEED to be done in 2-5 years anyway due to FAILURE. While he's got the time, he should get it ALL done. If he just wants to get it through the winter, and he's thinking of selling it, then, by all means, replace only whats NEEDED.

OK....did I miss anything


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## brad96z28

TLS said:


> Any of you other guys here actually HAVE this same truck with this problem?
> 
> Mine overheated in the Summer when towing. Where's the plow blocking airflow problem there? Going down the highway.....where's the electric fan there? It was running, remember. These trucks ran hot. And were on a fine line when they left the factory.
> 
> Yes, it is an airflow problem. Replacing his clutch fan and T-stat is likely all he needs to do. Hot wiring the aux. electric fan to either a switch, a temp switch, or hot all the time will help, but NOT be a cure all. It's a low rpm 10" shroudless AUXILLARY fan. Have you guys actually SEEN this aux. fan? With all that fancy wiring and what not, the fact is, this tiny fan is only good for creating a slight breeze which may help activate the thermo coil on the clutch fan.
> 
> His problem is the age of everything guys. It's a 10+ year old truck. My similar/exact truck started having problems well before that age.
> 
> When I mentioned the water pump, I NEVER indicated that it was the *cause* of his problem. For a BBC water pump to last 10 years is stretching it. However, replacing a clutch fan that was rigged to stay locked up all the time, and draining coolant to replace T-stat and radiator, your freakin ******** not to put a new water pump on it WHILE all of this is off. Hell, if it had a ton of miles on it, I'd say to throw a timing chain on it as well! You guys are thinking like mechanics, I'm thinking logically.
> 
> If he plans to keep this truck, ALL of these things will NEED to be done in 2-5 years anyway due to FAILURE. While he's got the time, he should get it ALL done. If he just wants to get it through the winter, and he's thinking of selling it, then, by all means, replace only whats NEEDED.
> 
> OK....did I miss anything


Hey might as well put in some new spark plugs and a new gas cap.Cant hurt either, but it wont fix anything either. Real mechanics do some simple testing first.Let see if we can get the truck in proper working order before he starts throwing unneded parts in it. :waving:


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## brad96z28

I'm certain this will answer any fan related questions so get out your test light and/or DVM and make sure whats working and not working before ya spend a fortune chasing a problem

[/QUOTE]

AGREED!!!!!!!!!!!!!!!!


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## RJ snow

TLS said:


> Any of you other guys here actually HAVE this same truck with this problem?
> 
> Mine overheated in the Summer when towing. Where's the plow blocking airflow problem there? Going down the highway.....where's the electric fan there? It was running, remember. These trucks ran hot. And were on a fine line when they left the factory.
> 
> Yes, it is an airflow problem. Replacing his clutch fan and T-stat is likely all he needs to do. Hot wiring the aux. electric fan to either a switch, a temp switch, or hot all the time will help, but NOT be a cure all. It's a low rpm 10" shroudless AUXILLARY fan. Have you guys actually SEEN this aux. fan? With all that fancy wiring and what not, the fact is, this tiny fan is only good for creating a slight breeze which may help activate the thermo coil on the clutch fan.
> 
> His problem is the age of everything guys. It's a 10+ year old truck. My similar/exact truck started having problems well before that age.
> 
> When I mentioned the water pump, I NEVER indicated that it was the *cause* of his problem. For a BBC water pump to last 10 years is stretching it. However, replacing a clutch fan that was rigged to stay locked up all the time, and draining coolant to replace T-stat and radiator, your freakin ******** not to put a new water pump on it WHILE all of this is off. Hell, if it had a ton of miles on it, I'd say to throw a timing chain on it as well! You guys are thinking like mechanics, I'm thinking logically.
> 
> If he plans to keep this truck, ALL of these things will NEED to be done in 2-5 years anyway due to FAILURE. While he's got the time, he should get it ALL done. If he just wants to get it through the winter, and he's thinking of selling it, then, by all means, replace only whats NEEDED.
> 
> OK....did I miss anything


TLS I suggest that you put that flow chart to work also...The aux fan is not a low rpm fan. It should be running at about 1000-2500 CFM (thats cubic feet per minute) so It'll be running at about 2K-3K rpm which is definetly not low rpm. As far as towing in the summer same air flow problems exsist only difference is that now we have an excessive load at low MPH rather than blockage of ram air, GM's mistake was to add A/C with a heavy duty package which is why the Aux fan was needed to acheive proper cooling levels while under heavy load ect. In the summer time towing case senerio I would be looking for loose or corroded wiring as to why the fan was running slow... The root problem still remains the same as with A/C installed the air has to pass through a heat exchange situation( a/c condensor) before reaching the radiator which increases ambient tempertures about 25F-50F depending on what the outside temp is. All said and done... the truck if towing should have the HD package for towing (w/ 4 core Radiator) with heavy duty suspension) Many of these trucks don't have the HD package and are being used for towing and running a 2 core radiator & light suspension ect.. So the mistake here is that the owner/operator is using a truck which was not properly set up for its application. While not trying to take the manufacturer side of this, many a guy went and bought a cab and chasis setup without the HD package added there holmes wrecker setup and ran into this problem. In my opinion if its a work truck don't bother with the a/c and try to run a dumper or wrecker and if you have to have a/c then make sure you include proper HD and suspension package along with it. The $1500 or $2000 saved isn't worth it in the long run. 

Oh ya as with a slow running fan try hot wiring to the fan motor and check run speed against the system being activated by the sender unit. If different check your wiring for loose or corroded wiring.

And logically speaking I think I'd rather do the diagnosis and repair a root cause than spend a fortune on what might be wrong, plus logically the middle of the season would be the last time I would be looking to do the required upgrades to achieve a HD package coolant system.


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## justme-

brad96z28 said:


> Hey might as well put in some new spark plugs and a new gas cap.Cant hurt either, but it wont fix anything either. Real mechanics do some simple testing first.Let see if we can get the truck in proper working order before he starts throwing unneded parts in it. :waving:


REAL mechanics also know enough to recognise common mechanical issues. Is everyone so blind these days by the OBD plug in and diagnose on todays vehicles? I don't have a 454, never had need of a big block, but I am well aware of their propensity for overheating and GM's consistant lack of adaquate cooling in those vehicles equipt. I am also well aware of the typical person's maintenance habits, especially on cooling systems. 
I'm gracefully bowing out of this one- I still stand by my suggestions and TLS's suggestions. 
I may still be a "kid" to some here, being just shy of 30, but I have been wrenching vehicles, mainly trucks and mostly GM since I was 7. We'll see what we'll see.......


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## RJ snow

I agree, we all may different opions as to the Why,When,& how to..But as long as the main objective is reached... "helpin a brother in arms out of a tight spot with a bit of sound technical advise that won't cost a bunch of money in the process." I really don't want to debate over the problem just help CK get his rig running without the worry of cookin the engine. 

CK... let us know what ya find out.

 

Waitin for winter to arrive...


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## CK82

Ok, I took the truck in had the T-stat replaced, and the radiator boiled (come to find out the radiator is a new steel core, not sure if its 2 or 4, I forgot to ask the tech. The tech said the radiator was fairly clean tobegin with so like a lot of you have suggest there is a lack of air flow. Anyways now the truck runs anywhere from 10 to 14 degrees cooler and runs about 195 at all times w/out the plow on. This week I will add the plow and take it for a test drive to see what happens. Sorry to get everyone worked up about this problem but you all have a point in some way. Thanks for the help so far, I will let you know what happens after I put the plow on. If this doesnt fix the problem, I will need to find a way to get more cooler air in through the radiator (better aux. electric fan, or HD clutch fan). What I'm really glad about is that so far I havent had to put a ton of money into this problem. 

Chris


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## TLS

Chris,

Glad to see you saw an improvement.

Chances are though, that if you fooled with the clutch fan, it's likely still the culprit. In addition to Genuine GM parts, you have Hayden and Flex a lite. Make sure you get the Heavy Duty or Severe Duty clutch.

Test drive it though now with the plow. See if you hear the clutch engaging.

Also to test it, get it hot (drive it around on a warmer day with the plow on), come home, pop the hood, and then shut the engine off. Grab the fan and see if it's easy or hard to move with your hand. If it rotates easily, the clutch is shot. If it's real stiff, you may be OK.


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## CK82

TLS:

Sorry to take so long to get back to ya...Had the truck and plow out for a small dusting a few days ago, the truck stayed a lot cooler, did get a little hot for 15 minutes or so while on the highway, but the T-stat has helped, I think the HD clutch/fan would also help, but I am happy for now! Thanks for the help guys. Chris


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## Rappa

I was having the same problem in my 05 2500HD. High speed would overheat every time. Took it in to the dealer, guess what they did... Installed an new HD Clutch Fan. Problem totally solved. 

On another note, I have the exact opposite problem with my 454, it runs at about 150 ALL the time. Maybe there is no Thermostat in it at all. Reading this thread has me questioning that now. 


Replace the fan.


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## LITTLEELVISDAN

Reviving an old post. 
64,000 original miles on truck.
I have a 1995 ck3500. 
Purchased new in 2018, 454 crate motor from GM. New aluminium oversize 4 core radiator, 2- 16 inch electric fans with external t-stat set to come on at 150 deg. Sounds like a jet engine coming down the street. You can feel the air rushing in from a foot in front of the grille parked. I can even make the fans run when the motor is off. New water pump and t-stat. I can get the truck to idle at 185-200 on a cool day. Drive it normal and it stays 185-200 on a cool day. Hit some hills and it goes to 210.. put my race trailer on and BAM 210-230 and can’t get below 210 and if I hit a hill it’s 230 and can’t recover even in Park at idle. 
Had the same problem with the factory 454 before we spun the main Bering due to a oil pump failure and blew it. 
Since the air and transmission cooler sit in front of the radiator I am having the transmission flushed in hopes of discovering the transmission cooler is overheating the incoming air. Cause when I open the hood everything including the radiator is scalding hot. Also have. Acowl induction hood going on to see if I can get all that heat out from under the hood. Looks to be no where for it to get out with stock hood..

Any help is appreciated.


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## Randall Ave

Sounds like you are not getting enough coolant flow. Is the lower hose collapsed under a hard pull, is the spring in it? What is the inlet and outlet temps at the rad when running hot


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## kimber750

What temp thermostat is in the engine? Do you have a tranny temp gauge?


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## LITTLEELVISDAN

Do not know what deg t-stat is currently. Also having that changed to 185. 

I will have them check the lower hose for the spring.. good idea...


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## dieselss

Raise the fan temp to about 180.


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## Randall Ave

You have checked to see if your temp gauge is accurate?


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