HELP...NO HEAT and it's -5!!

[jennyrockstar]

So my 2000 Sonoma decided that I don't need heat in the winter
So far I've flushed the radiator, cleaned the hoses, topped up all coolant, and replaced the thermostat. After all that she started producing heat but only when she was parked. Just cold air when I was driving her. The Tempreture gage would go to 125 then drop. I drove her less than a quarter of a mile with the temp gage on 125 thinking maybe a line was clogged and it might just blow it out, nothing happened but she did drop back down and a mile later over heated and all the coolant leaked out near the water pump. SO I've replaced the water pump and seals and she's still leaking antifreeze and no heat! WHAT NEXT? ("For Sale" sign I think!!)

 

[epiphaknee]

I wonder if the thermostat is in backwards? Did you really mean that the Temp Gauge indicated 125 degrees or did you mean to say that it indicated 225 degrees? Is the new thermostat rated at the proper temperature? I think it is either 175 or 185 degrees.

Did you remember to replace the GMC thermostat gasket which surrounds the thermostat? It fits very snuggly in the housing and works very well?

When the water pump was replaced was a gasket used between the pump and the engine? Did you threadlock the four bolts, so that coolant won't leak out of the bolt holes? You can pull them out one at a time and determine which one(s) is leaking because it will be wet. Properly installed bolts will be bone dry.

It sounds like the thermostat is not openning and then causing overheating very early on.

Of course the heater core could be clogged too. You can disconnect the heater hoses and flush backwards and forwards with water to try and unclog the heater core. If a lot of debris comes out you know that the heater core is plugged or partially plugged. Sometimes the heat will return and sometimes it will only return for awhile as it becomes clogged again.

"She still leaks" coolant? Because the coolant level keeps dropping and needing to be topped off or because you can see where it is leaking? If you can't see where it is leaking from then you have to consider a blown head gasket (can verify by consistency of oil) or compression test or consider the heater core. The heater core is on the passenger side (behind the dash) and you can usually just run your hand over the carpet near the dash and smell the coolant on your hand.

 

[jdauphney]

heater

your heater core is most likely cracked

 

[I_Heart_SLTs]

Food for thought

If by chance you went over the reccommended time for a rad flush
the Dexcool breaks down and will fill the heater core with debris

try this...

unhook the heater core lines, flush with water and compressed air,

Blow it through both ways for several minutes.

That will get you toasty again.

 

[02zr2silver]

Although this may not be related and this is a late response, all with no heat problems should read this. I have a 2002 ZR2 with 85,000miles. For the past 2 years I have been plagued with no heat, and in Michigan in the winter, that is not a good thing. I have done all of the following: 1. 2 HVAC fuses ok, 2. backflush both the heater core and complete system 3. new thermostat, 4. new heater core, 5. new vacuum pots-3, 6. new electric temperature door control actuator, and 7. new HVAC dash control module. And................. still no heat!!!!! So after taking the entire dash and heater box off for the 3rd time, I finally found the problem. The gasket which seals the heater box to the firewall was oozing out on the top, down into the swing area of the temperature control door. It interferred by about 1/4in. I discovered this with the entire dash and HVAC box out to get at the electric temperature door control actuator . Then by tying to move the acutator, I found I could not rotate the door to the heat position. With the box off, you could see the interference. So I simply trimmed it back about 1/4in and now the door can move effortlessly! I reassembled and everything OK!!

Another bad design to go along with a bad design heater core which clogs up from the top!! Good luck on your problem.