Poor Heat - 2007 Grand Prix GT

[runt]

On my 2007 GP in the past I've done the following:

 

 - New T-Stat.  195*F which is stock.

 - Bled cooling system with one of these:  https://www.amazon.com/EPAuto-Radiator-Coolant-Filling-Funnel/dp/B01I40ZQWE/ref=sr_1_2?ie=UTF8&qid=1508244770&sr=8-2&keywords=radiator+funnel+bleed

 - Checked/re-checked coolant levels.

 

My issue is this:  the car gets up to temperature just fine.  Once the T-Stat opens and I'm traveling at highway speeds (55mph or so) the temp on the gauge and inside the vehicle drops.  It isn't cold per say but it's chilly enough that my windshield won't get fully cleaned off.  My past W's were always HOT in the winter and this is lukewarm at best.  During the summer the temps get to the middle mark and stay there even in extreme heat it rarely moves above the middle.  Now I'm lucky to be on the first hash.  (there are 4 bigs lines on the 04+ so I use the middle one as 'where it should be')

 

This car doesn't have the metal cap so I'm thinking maybe replace that next. 

 

The only things done to the car are intake and I've removed the engine cover.

[Grandprix1]

Are you sure you bled it well enough? What coolant did you use? Was it the correct mixture?

 

 

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[vipmiller803]

Backflush heater core and rereplace tstat with different brand

[runt]

I bled it twice last winter to be sure.  Never did replace the coolant.  Color was good at that time I was closer to 53k miles. 

 

I have a feeling the backflush is what it needs.  Tstat was a good one but I'd do it anyway.  Might just do a full flush, backfill and see what it does.

[Psych0matt]

Same issue here, Mine was fine until I flushed everything twice, I have a feeling I got a bad thermostat I didn't notice the heat thing until last night, but mine acts like it has some air until I rev it a bit which seems to open it until next cycle

[94 olds vert]

My 2000 GTP had luke warm heat until I flushed the heatercore and replaced the coolant. I also replaced the T stat at that time. After that my heat was much hotter.

Edited October 17, 2017 by 94 olds vert

[Schurkey]

On my 2007 GP in the past I've done the following:

 

 - New T-Stat.  195*F which is stock.

 - Bled cooling system with one of these:  https://www.amazon.com/EPAuto-Radiator-Coolant-Filling-Funnel/dp/B01I40ZQWE/ref=sr_1_2?ie=UTF8&qid=1508244770&sr=8-2&keywords=radiator+funnel+bleed

 - Checked/re-checked coolant levels.

 

My issue is this:  the car gets up to temperature just fine.  Once the T-Stat opens and I'm traveling at highway speeds (55mph or so) the temp on the gauge and inside the vehicle drops.  It isn't cold per say but it's chilly enough that my windshield won't get fully cleaned off.  My past W's were always HOT in the winter and this is lukewarm at best.  During the summer the temps get to the middle mark and stay there even in extreme heat it rarely moves above the middle.  Now I'm lucky to be on the first hash.  (there are 4 bigs lines on the 04+ so I use the middle one as 'where it should be')

Backflush doesn't fix an engine that isn't warm enough.  Backflush may improve coolant flow through the heater core or the radiator.

 

Your engine isn't staying warm.  Faulty thermostat.  Are the cooling fans running?

[runt]

Just replaced that last year but might warrant another one.  Fans run as expected as far as I can tell.

[White93z34]

How much does the gauge drop off?

[runt]

Drops almost 1/4.  Gauge is at half when the car is "hot".  When the t-stat opens (i'm assuming) it drops to nearly 1/4.  Thinking I should flush the system and do another new t-stat. 

[Leadfoot]

Does it warm back up if you stop driving and let the car run while sitting still somewhere?  My bet is on a thermostat.  This is exactly what happened to me with a bad thermostat twice.  

[Imp558]

Did it do this when it had the old thermostat? I'm starting to wonder if maybe they gave you the wrong temperature stat. It will have the temperature stamped on the bottom of it

[runt]

Can't say it warms after sitting but it will warm up if I hammer on it.

 

Gonna do another t Stat and bleed the system down again. Havent had much time to check it out but it hasn't been cold either.

 

 

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[W30olds]

Air in the system maybe? Had the same issues when I replaced my radiator last year. Finally I bled the air out with the bleeder screws and that solved my issues. Good luck man!

[Psych0matt]

Replaced my thermostat tonight and made sure it was all topped up, will report back tomorrow. I've heard that parts store thermostats are kinda crappy for this engine so I ordered an ac delco for a few dollars more

[runt]

Been dealing with lack of heat in the house so haven't looked at this.  Will keep that in mind before I talk to my mechanic buddy.

[Psych0matt]

It helped marginally, but at this point I'm thinking my heater core is blocked up. I flushed everything up good in the spring, but I didn't do the heater core on its own so that's probably the issue now

[W30olds]

It helped marginally, but at this point I'm thinking my heater core is blocked up. I flushed everything up good in the spring, but I didn't do the heater core on its own so that's probably the issue now

Could maybe your blend door be stuck, or not working. Maybe the heater control valve?

[Galaxie500XL]

Could maybe your blend door be stuck, or not working. Maybe the heater control valve?

You reminded me of an issue I had on my '95 Cutlass that could apply here...I had a failed actuator that operated those doors on my old Cutlass, though mine failed open, which meant I had heat 100% of the time.

 

Mine had the electronic climate control, so it had actuators, rather than using cables or vacuum to operate the doors.  I honestly don't know what method is used on the 2007's...but if I were a betting man, I wouldn't be surprised if it uses actuators, too.

 

I about died when I saw what new ones cost---nearly $250.00.  After some patient searching, I found out that certain full sized GM pickup trucks used a different part number, but it was compatible.  Found one in a junkyard, on a truck that someone had already removed the dash--cost me $5.00, and about 5 minutes of work removing it---and nearly 2 hours to properly install it on my Cutlass.

[Galaxie500XL]

...AND...a couple of minutes with Google, and I think I have the answer..

 

2007 Grand Prix uses actuators for the blend door.

 

http://www.partstrain.com/store/details/Pontiac/Grand_Prix/Dorman/Heater_Blend_Door_Actuator/2007/RB604108.html?source=bngpla&utm_source=bing&utm_medium=cpc&utm_campaign=PTNBNG-SH-Brand%20Dorman&utm_term=1100006267481&utm_content=PTN-BNG-Brand-BR-Dorman

[runt]

Something to keep in mind! Thanks!

 

 

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[Psych0matt]

I'll have to look at this too, although mine worked fine last winter (but that was before I flushed the radiator and cooling system)

[Galaxie500XL]

IIRC, they fail most often after the battery has been disconnected...they go through their full range of motion, and generally fail by eating their internal gears.

[Psych0matt]

don't think that's my issue, I get warm air at higher RPMs

[runt]

don't think that's my issue, I get warm air at higher RPMs

 

Same here.  I'm sure, for me, it's either air or heater core needs a good flush.