# any shade tree mechanics help with chevy



## cincy snowdog (Dec 19, 2005)

One of my trucks is acting up,it is a 1998 k2500 with small block vortec,(4x4).
it just hit 59050 miles and is overheating.
when you start it and run for five mins or so it climbs to 210 ,at that time it has no heat inside the cab.
what is the issue:
1. intake gasket bad? dont spit out where it is visible.(a problem with these motors)
2. bad thermostat?
3. bad waterpump?(no noises ,maybe impeller broke inside?)

it was overheated while it was being driven before it was noticed.(heads damaged now? 

where do you think i should start,waterpump then thermostat,then if no results intake gaskets.
any help will be greatly appreciated .
HAPPY HOLIDAYS to all


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## terrapro (Oct 21, 2006)

first check to see if you have any antifreeze. when the water pump goes bad it leaks all the antifreeze out from a weephole. second i would replace the thermostat which from what you describe is what it sounds like it is, the thermostat is not opening to let the coolant circulate which is why the heatercore is not getting any heat

plus the thermostat is much cheaper than a waterpump so if you are trying to rule things out i would start from the bottom. it probably wouldnt hurt to put in a slightly cooler one, yours is a 195 id go with a 185 if you can find one but youll probably get the 180. if it runs the same as it did before you let it over heat than you are probably very lucky and you didnt do any damage. just cross your fingers and dont drive it unless you really have to.


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## TenOfClubs (Dec 19, 2006)

probably a thermostat, but of course make sure the coolant level is up. avoid any colder thermostats with FI vehicles. If the coolant temp is lower than what its supposed to be, the PCM will enrich the fuel mixture (like a choke would with a cold engine) and this rich mixture will make quick work of your catalytic converter.

Im not sure if 98 has the "expensive" thermostat or not. (I dont think so) but the newer ones come complete with the housing, and come in a box the size of a heater core! those are expensive.


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## Robhollar (Dec 27, 2003)

To Start with Id do a coolant pressure test while it was running and lets see if it holds 15 lbs of pressure. Also see while under pressure if its blowing out the tell tail white steam out of the exhaust. If its not holding pressure or its blowing steam your prob looking at a bad head. 

Now we have to think why did it overheat in the first place? It will be my bet you prob will find your water pump has taking a dump. Or you may have a stuck thermostat. How I find if the thermo is stuck Ill use a non contact inferred thermometer. While its running Ill check the temp difference between both sides of the thermostat housing. 

The are other things that can be causing your probs. You could be air locked or your radiator maybe plugged. Last but not least anytime I do any coolant service I always change the rad cap. It my not need it but I feel better be safe then sorry. Im a bit of a freak when it comes to the maintenance of cars and trucks. When it comes down to it change the water pump, thermostat, and rad cap. While everything is all apart completely flush the coolant system with fresh water but be careful with the heater core. You can easily damage it with to much pressure. Do this and ill bet your coolant trouble will be min...Rob


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## poncho62 (Jan 23, 2004)

*They about covered it in the above posts......Do not go with a cooler thermostat. *


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## terrapro (Oct 21, 2006)

poncho62;341608 said:


> *They about covered it in the above posts......Do not go with a cooler thermostat. *


i dont know if you guys are speaking from experience but i am. i have replaced the thermostat in 3 chevy vehicles with colder ones. 2 1990 trucks w/5.7TBI and an 89 S10 blazer w/4.3TBI all of them had a better idle after warmed up and got 1-2 mpg better gas milage afterwards. im pretty sure that 160 is the temp when the comp goes into closed loop mode so having a 180 stat will not effect the gas milage the way you guys are saying it will. i guess you dont have to take my advice but i have only had positive consequences from replacing my thermostat.


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## TenOfClubs (Dec 19, 2006)

the vehicle goes into closed loop as soon as possible. that usually means as soon as the O2 sensor comes online. That requires heat from the exhaust in those old chevys, as they only had single wire sensors, the newer ones are heated sensors, and are operational much sooner. 

the early Chevs were about the only manufacturer that was too cheap to have an O2 without a heater, thus they programed their pcms to operate as such, and put less dependency on the 02 than other vehicles. 

the old Chevys you listed are speed density systems, and are prehistoric in the auto motive industry. I still wouldnt use a lower temp stat in that vehicle though. Along with melting down your cat, you contaminate your o2, contaminate the oil with excess gasoline, and usually get poorer performance.

the extra gasoline may lower combustion chamber temps, and prevent pinging which may allow the vehicle to run with more spark lead, thus giving it more power, but still contaminating the oil, and the atmosphere.


as much as we like to think we're smarter than the manufacturers, we're not.


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## PDQ Pete (Dec 22, 2002)

If your loosing coolent out of reservior when it gets hot, possible head gasket or cracked head.


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## cincy snowdog (Dec 19, 2005)

ok,worked on it for few today,thermostat changed(only had 195 degree) and water pump was circulating but it is losing a/f .
it is internal-burning out the exhaust and a/f in oil.
head ?
head gasket ?
intake gasket?
looks like the news years project .
Now would you rip the whole motor and get a jasper rebuild or just rip the heads off and rebuild it .(i can rebuild it but i was concerned as far as over heating the block)
thanks to all for the help and Happy Holidays.


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## cincy snowdog (Dec 19, 2005)

or the intake gasket first?


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## Robhollar (Dec 27, 2003)

Youve got head probs. Ya it could be just a gasket but theres no way im gonna tear it down and put it back together only to find the heads blown. Heads dont blow for no reason id still suspect the waterpump is bad. If it was me Id change the heads, waterpump thermostat and flush the coolant system to be safe. After all if your gonna be that far into it you might as well change the pump too. Better be safe then sorry...Rob


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## B&B (Nov 4, 2006)

Robhollar;341769 said:


> Youve got head probs. Ya it could be just a gasket but theres no way im gonna tear it down and put it back together only to find the heads blown. Heads dont blow for no reason id still suspect the waterpump is bad. If it was me Id change the heads, waterpump thermostat and flush the coolant system to be safe. After all if your gonna be that far into it you might as well change the pump too. Better be safe then sorry...Rob


I agree! While the Vortec heads are an outstanding head as far as their efficiency to make power, they will crack in a hurry when subjected to an overheat condition due to their thin wall castings.I'd pull the head's too.


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## cincy snowdog (Dec 19, 2005)

The initial cause was the thermostat i believe.
Would you feel safe keeping the block?
Also would you scrap the heads or magnaflux them first?Buy new or junk yard?
I have heard of the intake gasket causing this,any thoughts?
This is still a clean truck,so its worth fixing.


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## poncho62 (Jan 23, 2004)

*If you have antifreeze in the oil, there is a possibility of bearing damage. Best to check that out too.
*


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## Ding (Nov 13, 2006)

If you find the heads are bad you can get new heads with valves already in them, yes new (not rebuilt) with complete valves for $250 a piece. Or just go with a crate motor (exact replacement) for around $2000. I use Pace or Scoggins-Dickey. Of course you have to supply the labor or have someone else do the work. I usually go with an entire engine unless it is minor damage.


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## cincy snowdog (Dec 19, 2005)

yeh we will start pulling it apart this week ,i will find out which way i will go.
thanks to all for your input.


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## east end turf (Jan 24, 2006)

figure out how the antifreze is getting out first by looking at the plugs and doing a leakdown test figure it out before you start just throughing new parts at it could be intake manifold gasket the spark plugs should tell you where its coming from if its on top did the problem start with a plow on the truck ? my 94 chevy overheats on highway if your not watching the guage!! just courious? i went to a 180 thermostat with no ill effects so far 4 years and 30 0000 mi


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## WetChicken (Dec 23, 2006)

Wow, I am surprised that no one said to check plugs until now!

If changing pump, thermostat, heads, etc you might as well do the radiator (if it is in question and the budget allows), hoses, and belt(s). Nothing like that warm fuzzy feeling of security when you're out at 2AM.


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## cincy snowdog (Dec 19, 2005)

east end turf;342713 said:


> figure out how the antifreze is getting out first by looking at the plugs and doing a leakdown test figure it out before you start just throughing new parts at it could be intake manifold gasket the spark plugs should tell you where its coming from if its on top did the problem start with a plow on the truck ? my 94 chevy overheats on highway if your not watching the guage!! just courious? i went to a 180 thermostat with no ill effects so far 4 years and 30 0000 mi[/QUOTE
> it overheated because of the thermostat, it runs fine ,just kicking the a/f water out the exhaust.
> Last year one of our other chevys starting leaking(visible on top) from the intake,we replaced gasket and its been fine .
> What kind of color would i look for on the plugs?
> thanks for the advice to all.


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## B&B (Nov 4, 2006)

If it's burning the coolant you should be able to see it on the plug's. They'll usually have a heavy white "crusty" build up on them,


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## east end turf (Jan 24, 2006)

Look For Any Color Difference When You Remove Plugs Then When You Find The Different One You Can Pressure Test That Cylinder. That Is As Simple As Puting A Low Pressure Air Source In Cylinder And Listening To Where The Air Is Going Some Air In Crankcase Is Normal Snap On Or Mac Or Craftsman Makes A Tool For This . Oh Make Sure The Piston Is At Top Dead Center Or The Air Will Come Out One Of The Valves! Also The Air Might Come Out Of The Radiator If The Head Gasket Is Bad ! Hope This Helps Let Me Know How You Are Making Out!!


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## RYDER (Sep 19, 2005)

Check the heater core.


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## NorthernILPlwr (Oct 20, 2006)

Im an ASE certified master automobile tech. The vortec engines have major problems with the intake gasket. The OE gasket ALWAYS fails. You will then get the problems you are experiencing. GM has not come out with a replacement gasket that fixes the original problem. FEL-PRO has. They use a metal core on the intake gasket where the OE gasket was prone to fail. Pull the intake off and replace it with FEL-PRO part# MS98000T
Shown Here:









If you overheated it change the thermostat. Only use the OE temp thermostat. The truck will overwork itself trying to reach operating temprature. These engines were made to run efficently at about 210 degrees. If you lower that temp the truck will not get optimum fuel mileage, heat, etc etc.

Hope this helps!

-NIP


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## suzuki4life (Nov 14, 2006)

i have the same truck/ engine. It has had the intake gasket replaced at 73K. I bought it at 75K and it was leaking coolant, never overheating though, so i replaced the waterpump and its mint. Not sure what temp themo it has in it.



-zach


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## east end turf (Jan 24, 2006)

Hey Northern What Do You Mean By Over Work ? Too Much Timing Too Much Fuel?


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## east end turf (Jan 24, 2006)

Cincy What Have You Found?


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## NorthernILPlwr (Oct 20, 2006)

suzuki4life;345244 said:


> i have the same truck/ engine. It has had the intake gasket replaced at 73K. I bought it at 75K and it was leaking coolant, never overheating though, so i replaced the waterpump and its mint. Not sure what temp themo it has in it.
> 
> -zach


he said he had coolant in the oil and vice versa



east end turf said:


> Hey Northern What Do You Mean By Over Work ? Too Much Timing Too Much Fuel?


yea exactly. The computer will adjust fuel trim and timing to try to warm the truck up. If you start your truck up on a cold morning ad drive until it gets warm your fuel mileage will be less than a truck that was already at optimum operating temprature. The computer adjusts for engine temprature. Thats why when a computer temp sensor goes bad the truck runs like crap. Its adjusting for what it thinks is a cold engine.


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## Zippy (Oct 20, 2006)

I have an 87 GMC with the 350 TBI in it. When I bought it I was having the same troubles that you are describing. It ended up being the intake gaskets. 

Kevin


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## cincy snowdog (Dec 19, 2005)

just to let you all know we have it on the road ,it was the intake gasket was leaking down into motor. changed the gasket,changed the oil twice and so far three thousand miles it going strong .thanks to all who responded.


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## Foxfire (Sep 25, 2003)

*Chevy*

Yes but wouldnt it just be smarter & cheaper to buy a FORD ? Just makes sense to me ..... I dono. Just my thought !!!


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