Heat Problem

[TheIceFishingKid]

I have a 2001 Chevy Blazer. When you turn on the heat it will put out warm air but not as hot as it should, the car is still really cold in the winter. I thought it was the heater core that was the problem but I replaced it and it did nothing. I also have had the radiator replaced along with most of the hoses. Has any one seen this problem before? Thank you for any help.

[Macgyver55]

I assume you have already done the thermostat? If not do it...

another thing to check would be the blend door and controls.

[Jeremy airjer W]

I would also be suspicious of the T-Stat. If the temp guage never gets to approximately the mid position than that is possible the cause.

The blend doors on this one are electronically controlled on both the manuel and automatic climate control.

[Hafnutz]

A common problem on GM vehicles with no heater output is caused by a leaking AC condenser. The AC condenser and the heater core are in the same enclosure under the dash. The condenser springs a leak and the refrigeration oil runs out. Then all the dirt and misc junk that gets in through the air intake sticks to it and plugs it up. No air can pass through and get into the vehicle. A simple cure is to remove the blower motor and flush the plugged a/c condenser with some brake cleaner. I like to follow this up with some degreaser and rinse with some water. All the junk will run out through the a/c drain and under the car. Your a/c still won't work but the heater will. I've done this to several older GMs.

[Jeremy airjer W]

I think the air flow is not the problem from what I understand. Its just not blowing very hot air. Would this be a correct assumption?

[TheIceFishingKid]

airjer

That is correct, the air flow is great it just wont heat up. I can't remember if i replaced the thermostat on this vehicle or the other one. They are cheap enough I will just replace it and see what it does. I will let you guys know. thanks you the help.

[Scott K]

That would be my first move to replace a t-stat, even new ones have been known to cause problems!

[TheIceFishingKid]

Heres an update.

It is still a no go. This was the vehicle I replaced the thermostat in, but I went ahead and changed it again. Also the blend door does not appear to be the problem.

A friend of mine told me that the seal on the radiator cap and/or reservoir tank may have a leak that is allowing air into the system. Does this sound possible to anyone. Because doesnt air in the system usually cause the car to run warmer, thus the temp gauge would read warmer. But the car isnt running any warmer then when it worked.

Just an FYI this all started shortly after the radiator was replaced, but my family mechanic assures me it has nothing to do with the radiator being replaced. I am starting to think other wise.

Any more help would be great, I prefer to do as much work on my cars as possible.

Thank you

[Scott K]

Are the heater hoses that go into the heater core getting hot? Is one hore cooler then the other hose?

[TheIceFishingKid]

They both seem to be just as hot. I was looking at it again today and when I was driving it I turned on the heat. For about the first 5 sec. after turning it on really hot air came out but then it went back to cool/warm air. It has not done this in the past, in the past it just starts out cool and continues cool.

[Scott K]

Well if the hoses are hot going in, but you dont have hot coming out of the vents, then you either have a bad blend door, or a plugged heater core.

[Jeremy airjer W]

If the heater core is new than I would bet that you have either an air pocket in it or its defective. The fact that you had heat for a couple of seconds tells me that the coolant in the core was hot enough to supply heat. The question is..is there enough getting into the heater core (air pocket, restricted flow.

This will make a mess but might be worth trying. Remove both of the hoses from the heater core. Have somebody start the engine, as soon as you see what hose is supplying coolant to the heater core shut off the truck. Install that hose back onto the heater core. Pinch off the other hose and leave off the heater core. while keeping the radiator full have somebody start the truck again. Continue to keep the radiator full and stop the engine as soon as air free coolant comes out of the heater core. Install the hose and try to shut off at the same time to prevent air getting into the heater core. Top of the radiator and let run without the cap. Keep the heat on full hot and the fan on low. Let the vehicle warm up fully, hopefully you will have heat!

[Shack]

If airjers tips do not help, worn or loose impeller blades on the water pump could also be suspect. I am not a chevy guy, but I have seen it in Fords.

It can cause poor circulation, just enough to get the hose hot going into core, but not fast enough to keep air warm after blower motor blows air threw core.

I figured everything has been thrown out .

Edit:I just read closer. I am sure it is an air pocket. May I ask why the radiator was replaced?

[TheIceFishingKid]

I believe the radiator was replaced because it had a pin hole leak and it was under warranty. That really does sound like a mess but I guess it must be done. I will not have time this week but I will let you guys know what the out come is next week when I do this.

Thank you to every one that has given me some input and if you have any futher input it would be helpful.

[TheIceFishingKid]

Well I know it has been awhile since I posted this but I just got around to fixing the problem after driving to Fargo and spending 4 hours in a car with no heat when its -25 outside. Man did that suck.

I was going to do what airjer suggested but thought I would start out by taking off some other hoses first, to try and keep the mess down. I found the air pocket on the first hose. It was one of the hoses that come off of the heater core that goes into the water pump.

I have been driving around with heat for a week now, but today on the way into work I noticed the air is getting cooler again. I have no coolant leaks and I am wondering how the air is getting into the lines. I have noticed that the car seems to be running a lot cooler than normal. Any more thoughts.

Thank you guys.

[Jeremy airjer W]

Make sure the coolant is still full! If there is less heat and the coolant temp is low it usually means the t-stat is stuck open/broke. I think your next step is to replace the t-stat.