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  1. #1
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    Default Persistant Heater Issue

    I have a 2006 Grand Prix that I've been having problems with the heat on for the entire winter. Back in early December, I discovered that I was only getting barely warm air from the heater. It was about this time that I noticed the engine temperature not getting up to where it needed to be. I replaced the thermostat. This took care of the low engine temperature, but the heater problem persisted.

    The next thing I noticed was that the hose going into the heater core was hot, but the one coming out was only warm. I knew I needed a coolant change anyway, so I had a mechanic change the coolant and back-flush the heater core. After this procedure, my heat was excellent...for about two weeks. After this time, it was back to only slightly warm air coming from the heater. Another thing I noticed after the change was that I couldn't keep coolant in it. This was a problem I had a couple of summers ago. It had stopped leaking, and hadn't given me any problems since. I'm guessing the combination of a flush and new coolant reopened the leak. After searching for a leak, I finally found that one of the coolant elbows was cracked. I replaced both elbows with aluminum replacements. No leaks, I haven't had to add coolant since, but I was still just getting slightly warm air coming from the heater.

    Fast forward about a month, and I am down to NO heat. It's much warmer to turn it off than to leave it blowing on heat. I've tried the knob, and you can hear the blend door opening and closing. You also can feel the difference between freezing cold air, and just cold air as you switch between cool and hot. The air coming out when it is set to hot is not remotely warm. It's not even room temperature. It's cold. What I've discovered is now, both the hoses going into the heater core and coming out of the heater core are barely warm. They feel like the only warmth on them is due to the engine heat. They aren't remotely as warm as they are supposed to be.

    Along with that, I'm also seeing swings on my temperature gauge. It will swing from the "quarter" mark up to halfway, where it normally would run, and back down to the quarter mark. I say it like that because I'm not certain what temperature the marks represent. Normally, shouldn't it warm up to operating temperature, the thermostat open, and just hold that temperature?

    Does anyone have a suggestion of what may be going on? I'm about out of ideas.

    Thanks,
    Last edited by Singlealt; 03-20-2017 at 07:22 AM.

  2. #2
    GT Level Member mguzzo's Avatar
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    Default Re: Persistant Heater Issue

    First step would be to re-bleed the system. You can search for ScottyDog's procedure, or briefly;

    take off radiator cap, start the car. turn the heater on full blast.
    make sure radiator is filled as the car runs and warms up. when the t-stat opens the coolant level will drop, keep filling it.
    once the T stat opens, put the radiator cap on and run the car a few more minutes, any air will come up to the bleeder screw on the T stat housing
    crack open the bleeder screw and run the car until you get a steady stream of coolant. close the bleeder screw.
    check the heat and temperature gage. you should be at operating temperature, the temperature needle should be steady and you should have good heat.
    If everythings good, shut off the car and make sure the overflow is filled enough.
    --
    Current '98 GTP Coupe: Still stock and rust free. That will change.
    Old '98 GTP Coupe: VS Cam, 3.0, S2IC, 42.5#, TOGs, N*/LQ4, Corsa. it once ran a 13 flat
    Older '98 GTP Sedan: Pullied, rockered, SSIC, etc. Stock 14.33 @ 96.5 / PB: 13.89 @ 101

  3. #3
    Killa Bee Scottydoggs's Avatar
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    Default Re: Persistant Heater Issue

    flush your heater core.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, 2.8, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW

  4. #4
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    Default Re: Persistant Heater Issue

    So basically you think the heater core hoses could be air locked? Would I not see the level in my reservoir drop?

  5. #5
    Killa Bee Scottydoggs's Avatar
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    Default Re: Persistant Heater Issue

    these cars always get air trapped in the core. take both hoses off the alt bracket, flush both hoses with a garden hose till clear water comes out. replace the two hoses and try to keep the hoses filled with water.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, 2.8, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW

  6. #6
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    Default Re: Persistant Heater Issue

    Quote Originally Posted by Singlealt View Post
    I have a 2006 Grand Prix that I've been having problems with the heat on for the entire winter. Back in early December, I discovered that I was only getting barely warm air from the heater. It was about this time that I noticed the engine temperature not getting up to where it needed to be. I replaced the thermostat. This took care of the low engine temperature, but the heater problem persisted.

    The next thing I noticed was that the hose going into the heater core was hot, but the one coming out was only warm. I knew I needed a coolant change anyway, so I had a mechanic change the coolant and back-flush the heater core. After this procedure, my heat was excellent...for about two weeks. After this time, it was back to only slightly warm air coming from the heater. Another thing I noticed after the change was that I couldn't keep coolant in it. This was a problem I had a couple of summers ago. It had stopped leaking, and hadn't given me any problems since. I'm guessing the combination of a flush and new coolant reopened the leak. After searching for a leak, I finally found that one of the coolant elbows was cracked. I replaced both elbows with aluminum replacements. No leaks, I haven't had to add coolant since, but I was still just getting slightly warm air coming from the heater.

    Fast forward about a month, and I am down to NO heat. It's much warmer to turn it off than to leave it blowing on heat. I've tried the knob, and you can hear the blend door opening and closing. You also can feel the difference between freezing cold air, and just cold air as you switch between cool and hot. The air coming out when it is set to hot is not remotely warm. It's not even room temperature. It's cold. What I've discovered is now, both the hoses going into the heater core and coming out of the heater core are barely warm. They feel like the only warmth on them is due to the engine heat. They aren't remotely as warm as they are supposed to be.

    Along with that, I'm also seeing swings on my temperature gauge. It will swing from the "quarter" mark up to halfway, where it normally would run, and back down to the quarter mark. I say it like that because I'm not certain what temperature the marks represent. Normally, shouldn't it warm up to operating temperature, the thermostat open, and just hold that temperature?

    Does anyone have a suggestion of what may be going on? I'm about out of ideas.

    Thanks,
    Once the car is up to temperature, the temperature gauge can fluctuate a little bit, depending on the outside weather, your driving speed and whether the fan for the radiator is blowing or not. But it is a gradual slow change, not jumping. Maybe bleed the system is a first thing to do.

    Regarding no heat, it looks like the heater core is clogged. So it might make sense to flush it. I am not sure how often a heater core can be air locked but bleeding the system could help that I guess.

  7. #7
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    Default Re: Persistant Heater Issue

    I think your initial clogged heater core was cleared of the obstruction on your first flush and it may be clogged again. You might want to do another heater core flush again as well and flushing your entire system with water 2-3 times until it runs clear. And like the others mentioned be sure to do a proper bleeding/burping of the system. Lisle spill free funnel can be helpful with this.

  8. #8
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    Default Re: Persistant Heater Issue

    Take it from Scottydoggs had same problem couple years ago he told me to flush heater core had to do it twice.First time heat lasted a couple days had to do it again been good now for a few years

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