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1999 GMC Jimmy No Heat...


T Rex

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First, I have never had heat in the Jimmy since I've owned it, something Ive been meaning to fix. At school a week ago my temp gauge climbed up to max temp so I kicked on the heat (to see if it would work at all) and it DID! I couldn't believe it. I went to Napa and bought some stuff with dex-cool in it and put it as soon as I got home. When I opened the radiator cap there was almost a 1/4 inch of gunk stuck to the bottom of the cap. I cleaned it off well and filled it up with the dexcool. Turned the car back on and no heat. :/

 

So, after reading lots and lots of issues with Jimmys/Blazers and no heat I decided to flush the radiator fluid and put in some regular antifreeze and get rid of the nasty dex-cool (Its probably the stock fluid, yikes, only saving grace is the truck only has 65k on it). Anyway, I flushed it and got LOTS of crap out but still no heat.

 

I searched some more and found that if I need to get the car hot and feel the two hoses that go to the heatercore, well Im not 100% sure if it was because they both sit right above the engine or if there was warm coolant flowing through the lines but they felt warm. I should also note that when I squeezed the lines it felt like there was stuff cracking in there :/.

 

My next step is to take the left hose (return hose I believe) off and run water from my garden hose backwards through the heatercore to see if there is a clog somewhere. I need to burp the coolant system too... forgot about that.

 

Oil is brand new and full.

 

Also, Im VERY confused that I had heat when I had low coolant. What explains that? Searching on google didn't come up with anything worthwhile.\

 

Any other suggestions?

 

Sorry for the long read!

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No, the temp gauge reads 195 steady.

 

The owners manual says that it should be a 15psi radiator cap and the one on there is a 16... does it matter that much? I should probably replace it anyway though.

 

if it holds pressure your good... if not then replace it...

 

 

heater might just be packed full of shit...flush it, and retry it ;)

 

and the heater hose should be as hot as the radiator hose

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properly bleed the cooling system. find a plug, port or sensor on the motor as high as possible, remove the mentioned component and fill radiator with coolant until you see a small amount of coolant seep out. seal removed component and clean surface area before reinstallation. that should remove the majority of air from your cooling system. Run the vehicle cold with the cap removed taking note to add coolant as need until no more air escapes and your done.
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