# 99 Silverado No Heat



## Outty330 (Dec 4, 2008)

Had the truck in the shop mechanic stated thermostat was bad also claimed the water pump was "seeping" through the weep hole now ive have been under the truck in my garage several times before and saw no fluids so i found it hard to belive the "seeping" thing also fluid level has been were it should be.Wanted $500.00 to fix both I have a warranty but these issues are not covered go figure. So I told them to go ahead and change the thermostat @ $122.00 Seemed to work better for a few days when the outside temp has been above 30 degrees and now that it has been alot colder it will not blow hot air at all would a "seeping" water pump cause a no heat situation? I do not want to take it back and have them just keep throwing parts at it $$$$$ until they find the issue. Thanks in advance!


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## gearhead (Nov 30, 2004)

feel your heater hoses and see if they are getting warm-hot, you might need to flush the heater core.


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## Rubicon 327 (Oct 6, 2009)

Wouldn't be the 1st time a new t-stat went bad, I've had them be bad right after installation.

Just a ever so slight weep from the pump shouldn't do that, he may not have bleed all the air out of the system also.


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## 06Sierra (Nov 30, 2008)

The fluid in the overflow is good, but how about the radiator? Is it full?


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## Outty330 (Dec 4, 2008)

Thanks Gearhead, Checked heater hoses before I took it in to the shop top one was warm/hot lower was cooler.

Rubicon 327 so your saying change the thermostat again also with this being a sealed system with no radiator cap how would you bleed the air out. Sorry dont mean to act stupid just not up to speed on this type of system, thanks again!


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## overtime (Nov 5, 2009)

Just leave cap open and fill and run keep a funnel in overflow keep it about 1/4 full and just keep eye on it that what we do in the shop.


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## Outty330 (Dec 4, 2008)

thanks overtime I'll give it a shot when I get home from work, kinda sucks one of the coldest days here in central NY with lake effect flying and I got no heat :angry: sure was a dam cold ride in this morning!!


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## Gear_Head (Apr 29, 2009)

Outty330;931259 said:


> Had the truck in the shop mechanic stated thermostat was bad also claimed the water pump was "seeping" through the weep hole now ive have been under the truck in my garage several times before and saw no fluids so i found it hard to belive the "seeping" thing also fluid level has been were it should be.Wanted $500.00 to fix both I have a warranty but these issues are not covered go figure. So I told them to go ahead and change the thermostat @ $122.00 Seemed to work better for a few days when the outside temp has been above 30 degrees and now that it has been alot colder it will not blow hot air at all would a "seeping" water pump cause a no heat situation? I do not want to take it back and have them just keep throwing parts at it $$$$$ until they find the issue. Thanks in advance!


My hoses were getting warm at best and my overflow antifreeze tank was low on fluid. New water pump and the heat is awesome again.


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## Rubicon 327 (Oct 6, 2009)

Outty330;931334 said:


> Thanks Gearhead, Checked heater hoses before I took it in to the shop top one was warm/hot lower was cooler.
> 
> Rubicon 327 so your saying change the thermostat again also with this being a sealed system with no radiator cap how would you bleed the air out. Sorry dont mean to act stupid just not up to speed on this type of system, thanks again!


Sorry I didn't get to your question but Overtime got it!

I wouldn't say you need to replace it, just that I have had new ones be defective right out of the box so it wouldn't be a surprise to me if it were bad.

As I think was mentioned you may want to back flush the heater core and also change the in cab/cabin air filters as I have heard that can be a problem believe it or not.

Let us know how you make out.


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## Outty330 (Dec 4, 2008)

Ok I'll try and burp the system and let ya know thanks for all the suggestions!


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## jadyejr (Nov 29, 2008)

Had the same problem, put in a new thermostat, than my radiator started leaking so i put in a new radiator and a new coolant reservoir, still no heat, but the reservoir was cracked, as was the radiator, so they had to be replaced anyways. Ended up flushing it, my mechanic tried a soft flush first since the core is a little fragile, had heat for a couple days than no heat again, he went a head and flushed it back and forth a few times at full pressure and alot of nasty fluid came out, luckily didnt break the core... Now i have heat.

I guess the main culprit on these trucks when it comes to the heater core is the dexcool, that gm recommends, it gets nasty, and gunky...

In fact theres a class action on it... http://www.thetruthaboutcars.com/gm-coolant-settlement-could-cost-hundreds-of-millions/


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## mossman381 (Nov 17, 2009)

You should flush your heater core. Disconect both hoses so you do not push the nasty coolant back into the motor or it will plug your heater core again. Flush it both ways. I use a garden hose to flush them.


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## Outty330 (Dec 4, 2008)

Flushed the heater core and I got heat!!!!!!!!!!!! Thanks for all the help guys. :yow!:


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## Rubicon 327 (Oct 6, 2009)

Glad to hear it!


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## Thermos017 (Dec 16, 2009)

did anyone put stop leak in the system? if so then just flushing the heater core itself is only a temporary solution. if the heat stops again get a chemical flush to add to the resevoir. follow the directions on the back of the bottle and flush the ENTIRE cooling system, not just the heater core. it's time consuming, but it's the only way to get rid of stop leak in the system. i've back flushed the core alone several times(takes about 10 minutes) on my wifes bravada and it works for 3 or 4 weeks then plugs up again. a previous owner had dumped stop leak in it and i haven't had time to do a full chemical flush yet. if that's the case for you too, then be prepared to replace or repair whatever part the stop leak was "fixing". once the stop leak is chemically flushed the leak will come back. And for future leaks, NEVER use stop leak unless you are stranded in the middle of the desert with no water and miles away from the nearest parts store. stop leak is an emergency only item. it is a bandaid that WILL damage parts with long term use. it starts with the heater core, and will eventually damage the radiator, t-stat and water pump.


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## Outty330 (Dec 4, 2008)

Thermos017 no it does not appear that there has been stop leak place in the system however it does appear that this fluid could be original hopefully I will be able to get through the winter with no addition issue and come spring I will do a complete system flush. The truck was an 1 owner trade and has been well taken care of and is in graet shape for a ten year old truck.


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## mikelawtown (Dec 5, 2004)

my buddy changed his housing-thermostat on his 5.3 and he didnt have any heat either so he let the truck run for an hour with no cap on it and after he replaced the cap went for a ride and heat now works..same as burping the system i guess..


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## mayhem (Aug 25, 2006)

The problem is the GM DEXCOOL coolant. It tends to create silt, not sure if its he coolant degrading over time or if its eating seals or what. The silt ges caught in the heater core and you lose all your heat.

Had this happen a cuople years ago, the plug of crap that came out of the core was like a pot of coffee grounds.

You're good for now, do a full lfusha nd fill in the spring and you'll be fine.


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## Thermos017 (Dec 16, 2009)

mayhem;944382 said:


> The problem is the GM DEXCOOL coolant. It tends to create silt, not sure if its he coolant degrading over time or if its eating seals or what. The silt ges caught in the heater core and you lose all your heat.
> 
> Had this happen a cuople years ago, the plug of crap that came out of the core was like a pot of coffee grounds.
> 
> You're good for now, do a full lfusha nd fill in the spring and you'll be fine.


thats all DexCool, not just GM's. and if you read your owners manual you will see that flushing the system and replacing the coolant is part of the scheduled maintenance for all vehicles that run dexcool. the purpose of the dexcool is to extend the life of the seals, not eat them. the brown sludge and chunks is caused by running the dexcool for much longer than it was intended. i believe the regular interval is 5 years or 150k miles. i personally go 4 years or 100k.

as far as the class action suite against gm, that was a copout on gm's part. they didn't want to admit that they were putting $#!t intake gaskets into most of their rigs and still do btw. by settling the class action suite (that only included 3.8 and 4.3l v6's from 95 to 04) they could avoid being forced to recall every v6 and v8 that they put the worthless plastic gaskets into. the problem with the gaskets wasn't the dexcool, but the higher heat at the back of the block would cook the plastic, causing it to get brittle, then crack apart creating a leak at the back of the block. in some cases chunks of plastic would run through the cooling system and end up in the heater core. depending on the rig that it was in, the leak was very hard to detect, and some ppl could only smell coolant, and never actuall saw it. the only reason imo that the heater cores were included was because most major shops wont just backflush a core. they would rather replace it with new parts and nail you from two directions for extra coin. they get the markup on the part, plus a helluva lot more in labor, than they would if they just backflushed the core.

In my experience, i have never had dexcool fail before it's scheduled maintenance interval, regardless of brand. it's all about taking care of your car before it brakes. if the coolant is starting to look more brown than orange/red, then its past time to change it. if you have 150k+ miles, or a rig over 5 yrs old (remember, the car was made 1 year before it's model year), change it. don't wait for the problems to occur. poor maintenance accounts for about 85% of my work. if you don't change your fluids at the proper intervals you are going to have problems. i tell all of my customers this, and yet the problems keep on comin [/rant]


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## Outty330 (Dec 4, 2008)

Hey Thermos017 can I run regular "green" coolent in the system instead of the Dexcool after I flush the system? Any harmful afects by doing this? Thanks!


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## Thermos017 (Dec 16, 2009)

Outty330;945761 said:


> Hey Thermos017 can I run regular "green" coolent in the system instead of the Dexcool after I flush the system? Any harmful afects by doing this? Thanks!


That is a personal preference as far as i'm concerned, however i tell all my customers to run oem. the new dexcool was designed to prolong the life of the seals in the newer rigs and parts. they won't last near as long if you run green. the seals for vehicles running dexcool are not the same as previous models, and they require the added lube and protection they get from the chemicals in dexcool. the only reason to change to green is if you don't want to change coolant as often. unfortunately if you run green, chances are you'll be replacing the coolant more often anyways, because you'll be replacing the water pump and t-stat gasket more frequently.

if you run green coolant in a rig, don't expect any warranties to be honored either. and i'm not saying manufacturer, i'm saying parts. if you sprang for the extra dough to cover a lifetime part and you take it in with green antifreeze dripping off of it they will probably tell you "sorry bout your luck". it's not going to destroy your engine to run green, but you are more prone to leaks, especially from your water pump and water outlet/t-stat housing. which, if not monitored, could lead to over heating and engine damage over time.

try to think of oem parts (including coolant) more like fuel or oil. if your car manufacturer told you to run 87 octane unleaded fuel, would you run 92 octane or diesel? if you did you'd find you get a lot lower gas mileage than you should if it runs at all, because your car was designed (and programmed) to run on 87. some rigs (fords) won't run worth a damn at all if you run too high an octane over the manufacturers suggestions. i know if you put premium in a ford 4.6L they get a helluva noise that sounds like the lifters are goin out, or like there is a rod knock almost. if they told you to run 5w30, would you run 5w20 or 10w40 and expect it to last as long as its potential? No. The same goes for ALL fluids you put into your vehicle. you don't have to run what they tell you, but i promise it's in your best interest.

as i said previously, its all about maintenance. follow the maintenance intervals in your owners manual and you shouldn't have the issues others are having. if you don't have an owners manual, contact your local dealers service department and they'll be glad to fill you in. if you look at all of the people having problems with dexcool you will find their rig is more than 5 years old, or has more than 150k on it.


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## Outty330 (Dec 4, 2008)

OK Cool Dexcool it is then thanks for the advice! I'll be sure to keep up with maintience truck has 97,000 miles and I would like it to last as long as possible.


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## jadyejr (Nov 29, 2008)

So what octane fuel should I run with the 6.0. I've been running premium, i've always had German cars and have always ran premium in them and gave been doing the same in my truck, what's the oem?


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## Thermos017 (Dec 16, 2009)

dunno off the top of my head. if you have an owners manual it will tell you what fuel to run. what is the year/make/model? what add-ons, if any, does the engine have? most newer gm's recommend 87 octane. GM is building their rigs for economy nowadays. that doesn't just mean getting the most mileage from your fuel, it also means getting the most mileage with the cheapest fuel. again, that is also a question your local dealer should be able to answer. don't ask a dealer though, ask the service department. most salesmen know one thing about cars, and that is to tell you what you want to hear, not what you need to know.


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## gearhead (Nov 30, 2004)

don't forget, never put tap water in with either the green or the dexcool


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