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Aluminator 12-29-2009 05:48 AM

99 Silverado No Heat
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. 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!

SlimJim 12-29-2009 09:20 AM

I can see no way a seeping water pump could cause a no heat condition. I have had seeping water pumps and you may not see any fluid coming out but there is usually a stain around the weep hole caused by the hot fluid coming out. Depending on how much is seeping out, you may have to add water occasionally. The thermostat is what I would have guessed caused the no heat condition. Feel your radiator hoses to make sure the engine is getting hot. It's not likely they installed a bad thermostat but it could happen.....or one with the wrong temperature range.

RUFFNECK4LYFE 12-29-2009 04:22 PM

The weep hole indicates a seal is leaking and the bearing is being washed with antifreeze. Which means it will lock up soon. As far as heat, check the heater bypass valve. That valve is either run by vacum or electrical. It has to open to let hot coolant run through the heater core.

acnas 12-30-2009 05:07 AM

I dont believe there is a heater bypass valve on a Silverado. It is possible that the leaking water pump could let air into the system causing a air lock in the heater core not letting the coolant flow. Gm water pump comes with the thermostat.

goldenhammer 12-30-2009 09:55 PM

What temperature thermostat did the tech install? Check your OEM rating. I just fixed the exact same problem on a freinds F150. Ran the engine for almost 20 minutes and no heat, no heat to the heater core hoses (they were cold). Installed a thermostat and still the same problem THEN i checked the rated thermostat temp and factory specs recommend a 195* degree thermostat. A good one cost $19.99 plus gasket and sealant. Everything worked fine afterwards, if there is no weeping at the seep hole check for antifreeze smell inside the cabin. There may be a leak somewhere else.

Aluminator 01-04-2010 06:13 AM

Well turns out the heater core was plugged flushed it and got heat. :D I'm thinking I will flush the system come spring and change the coolent is there a differnt option when it comes to coolent besides the dexcool gm puts in? I'm being told the Dexcool is what causes most of these issues.

RUFFNECK4LYFE 01-04-2010 03:44 PM

Additives is what causes this sometimes. Like the redline water wetter. It tells you to change the coolant after 12,000 miles. Cause it will break down and clump up the coolant system. I had dex-cool in my 2001 5.3 and just flushed it and put the green stuff back in. The dex-cool is mainly for aluminum heads. We have cast iron.

blueboy02 01-05-2010 11:55 AM

I had the same problem and i've talked with a bunch of machanics and they said if your going to switch from the dexcool to regular fluid you need to make sure the system if flushed completely because if it's not it will do the same and clump up and plug everything in your system. They told me to drain it and then fill it with water and a little dish soap run it for a minute, drain it, then repeat, after you've done that two times, fill it with just water, run it, drain it, then fill it with new fluid.

RUFFNECK4LYFE 01-06-2010 01:49 AM

Yeah I agree wit blueboy02. Better to be safe. So several flushes will assure its all gone.

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