I'm having a problem with the heater. After the Blazer warms up the thermostat stays around 160 degrees. The heater blows
a little bit of warm air. When I stop at a stoplight or something it starts blowing out cold air. When I start driving again it starts
blowing out the little bit of warm air. I am wondering if it is the thermostat not allowing the engine to get warm enough or if it is the
heater core. I read some posts earlier about the core leaking and were it is located. I have noticed a sound of swishing water behind the glove box area. Any help is greatly appreciated.

Eric

 

From reading other posts on this topic, I would say it sounds like you heater core is leaking. How is your coolant level? If some is leaking out of the heater core you'll probably notice it in your resevoir and/or radiator.

Most of the other posters will have better opinions than mine.

 

Hey there........My 4 wheel drive went out last week and NOW i have NO fricken heat!

1996 gmc jimmy

You need to flush out the lines with air and fill up again. Sludge builds up in there and it is suppose to help it by blowing it out. That will get rid of the noise under glove box too. mine had that......This is what I did, and I think i need to still replace the heater core. Trying to find out what else i can do on here. GOOD LUCK!

On my system the thermostat has been changed, whole system blown out by air and heat still is bad. Cold air is blowing out, but pressure of air is slow. There is not too much different between med and hi. Got any other suggestions? I really don't want to replace heater core.....

 

If your coolant resevoire is filled to the proper level and your heater is acting as yours is, the line from the coolant resevoire to the radiator may be clogged and not letting the antifreeze into the radiator. (Been there, done that!) If the coolant is that low, it will only circulate thru the heater core when the engine is at highway speeds. My 98 did the same thing and the temp guage did not indicate that it was running hot due to the low coolant.

If the vehicle has cooled down, remove the radiator cap and see if the radiator is low. I suspect it is. Fill all the way up and you should be good to go. If that is the case, you will need to blow out the line from the resevoire to the radiator. I would then drain and clean the resevoire.