Changed coolant and Thermostat still very little heat 2008

**veener79** · 11-15-2014

My wife said she noticed yesterday that she was not getting much heat out of her vents. The fan is working well but he temps are not there. Some times she would feel heat for a short time and then it would stop. Figured since the thermostat had never been changed it was a good chance because noticed the car was running a little on the cool side. Car has 93K on it. While at it I changed the radiator hoses. (what a pain to get to those clamps). Took the car out for a long drive. Even with the heat cranked to 90 it is comfortable in the car when 20deg out but not hot.

I am now worried it is a heater core. Been searching for help on this. I did not feel heater hoses to see if they where hot. Was going to do that after my wife takes it for long tomorrow. If it is a heater core what is the best way to try and fix it with out taking it out? Know that would be a huge job. Thanks for any help on this.

**Fivefingerdeathpunch** · 11-15-2014

Back flush the heater core first before you determine that the core is the problem.

It's kinda common to need to back flush the core to bring it back to life so to speak.

**idrivejunk** · 11-15-2014

Could also be an actuator issue behind the dash, there are electric and vaccum types both involved if you have a 97-03. If you hear any funny noises behind the dash as the car warms up, thats where I would look first because problems are common. The heater core job is a pain, but most of it is just moving the console and once the passenger seat is out its not so bad getting in there.

**Scottydoggs** · 11-15-2014

pull both heater hoses off the alt bracket, put a garden hose to either heater core hose, and fill it till clear water comes out the other hose. then put them back on.

your core has air trapped in it. this will fix it

**veener79** · 11-15-2014

Thanks will do the flush this afternoon. Bad part is this is my Wife's 3rd Grand Prix and the other two all had heater issues. Both the dealer could never get right. Hope I am better then the dealer she use to work with.

**Scottydoggs** · 11-15-2014

sounds like air trapped. happens all the time. every winter we get a influx of help i got no heat. 99% of the time, its just air a bound heater core.

**veener79** · 11-15-2014

Never had a car that could have this kind of issues so easy mostly when work is even not done to it. Must be a fun design flaw.

**stealthee** · 11-15-2014

Design flaw is GM's middle name.

**Scottydoggs** · 11-15-2014

funny but, its never happened to my car. ive flushed my coolant a few times, changed elbows, did a lim job, did a water pump, changed the radiator. none of that was at the same time either. not once has my heater core had air trapped in it yet.

seems to just happen to random cars here and there. why? i dont have a clue. but flushing it cures the issue.

**veener79** · 11-15-2014

Just flushed it. When I undid the bottom hose maybe a 1/8th of a cup came out. The hose was not at hot as the top. The top hose I had more fluid come out. Back flushed back and forth on each hose. First time forced fluid sounded like someone hacked up something. The fluid came out a dark deep red. Took flushing each hose 3 times (6 flushes) before the water would stay clear. Did if a few more times. Got the car back together and had heat almost as soon as the engine started. Just sitting in the car at it at 90deg for a few minutes in 20deg outdoor temps we had to turn it down. Now her car is all set for winter I hope. Thanks guys.

**Scottydoggs** · 11-15-2014

sounds like yours was clogged up with dex coolant sludge maybe. glad its all hot now.

**HighOctaneRacing** · 11-15-2014

Well it's good that you got it fixed but in the future if this happens on a another vehicle, just grab both the heater core hoses and see if one's colder than the other one. if it's colder than the other one then you know the heater core is clogged or has air.

**markpa** · 11-15-2014

Sounds like dexcool got you. Hope you out green back in. Also check the passenger compartment air filter. These get dirty quick.

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**veener79** · 11-15-2014

Changed out the filter last night also. Yes it got dirty over the last year or two. Not as bad as when I first did it after about 4 years because my future wife at the time did not know the car had one. Still running Dexcol because I knew I could not get all of it out of the block. Shocked how bad the heat core was because what came out of radiator was not bad. After taking off the hoses I looked at the block and it looked clean.

**Scottydoggs** · 11-15-2014

how to flush coolant.

remove the t stat, put the t stat housing back on, take the upper hose off the radiator, then push it down to the ground to a bucket or let it fly.

get your garden hose out, put it in the rad turn it on, then fire up the car, let it run till clear water pumps out the top hose.

then turn the hose off, run the car till no more water comes out the upper hose. then turn it off.

put your t stat back in, with new gasket, the upper hose back on.

now take 1 gallon of full strength green antifreeze, not the 50/50 crap. ( parts store cheap green is fine to use) dump the whole gallon in the radiator, fire up the car, fill the rad with hose water till its full. top as needed till its ready to be bled of air. it will burp and take coolant as the water in the block warms up the t stat opens up for a few seconds till cold coolant hits it and it shuts again.

now to bleed the air out, let it idle rad cap off till the fans turn on, (when the fans are on the temp is over 195 deg, the t stat is wide open) then open the bleeder screw on top the t stat housing a few turns till a steady stream of coolant comes out the hole, shut the screw, top off the rad. cap it.

done.

doing a flush this way will get most of the boogers out. you can flush to clean water, then add a flush kit, drive it some then fill and flush again, and then add new green coolant.

most of use have changed to green coolant.

**robinsone** · 01-04-2015

what he said, had the same problem, flush worked like a charm

**stocker** · 01-07-2015

Originally Posted by markpa

Sounds like dexcool got you. Hope you out green back in.
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I'm taking your comment too literally but telling someone (with less knowledge than veener) to "put green back in" would be bad advice. Flushing the system from dex to green is fine, obviously.

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