2008 Grand Prix Heat Issue

[Rtaft89]

Winters fast approaching and I'm getting cold! I had my HVAC checked out by the STEALership...$75 later, they told me they suspected a failed blend door actuator...and that they could replace it for upwards of $400. Well I replaced that myself....for $35.

Things I do know:
Blend door actuator is rotating left and right correctly
Coolant is full
Temperature gauge sits 1/2 way up after few minutes of cold engine start
Both upper and lower hoses get warm, with the top one more hot
AC blows cold
When changing the cabin temperature from cold to heat, a small temperature change is detected....to a luke warm temperature
I've never messed with a thermostat of a vehicle but from what I've read, I think I can rule that out.

Does this sound like a heater core issue?

Any advice is much appreciated! Thanks

[gmtech1]

Originally Posted by Rtaft89

Winters fast approaching and I'm getting cold! I had my HVAC checked out by the STEALership...$75 later, they told me they suspected a failed blend door actuator...and that they could replace it for upwards of $400. Well I replaced that myself....for $35.

Things I do know:
Blend door actuator is rotating left and right correctly
Coolant is full
Temperature gauge sits 1/2 way up after few minutes of cold engine start
Both upper and lower hoses get warm, with the top one more hot
AC blows cold
When changing the cabin temperature from cold to heat, a small temperature change is detected....to a luke warm temperature
I've never messed with a thermostat of a vehicle but from what I've read, I think I can rule that out.

Does this sound like a heater core issue?

Any advice is much appreciated! Thanks

How about the hoses on the heater core? are both hot, or is one much cooler that the other? Back flushing those is pretty easy.

[dagan06]

My heat is doing the same thing. One heater hose is much hotter than the other.

[Tech II]

Like GMTech1 said, if coolant level is ok, feel BOTH heater core hoses.....both should be about the same temp, and hot......if one is much cooler, than the core is blocked......try reverse flushing the core first....

[Lukas111]

Hi,
I have heating issue with my 2004 grand prix.
I changed engine month or so ago.
My car is heating very slowly, If I drive on fwy it will not heat properly at all, temp gauge will be about 1/4 or bit over.
If I drive in city, temp gauge will go close to 1/2 and over if I stop on red light. So it is not constant and vary a lot.
It does not loosing coolant. I assumed it was thermostat so I changed it but car seems to be doing the same thing.
water pump is not that old, i took it over from my old engine and it had about 20k miles on it or less.
Any other idea what it could be?
My mechanic told me that if there is no engine light car is running properly.
Asked me for $50 t replace thermostat so I decided not to deal with him anymore, I did it by myself.

Interesting thing was that I tried to bleed system and I release bleeding valve at working temperature and I get nothing out, not air or coolant. Hose was pretty hot.

[Tech II]

It certainly does sound like a thermostat, but you replaced it.....

This a 3.1/3.4/3.8?

Original coolant? Ever flushed?

Your bleeder could be plugged.....

Surprised a P0128 is not setting.....

[Lukas111]

Originally Posted by Tech II

It certainly does sound like a thermostat, but you replaced it.....

This a 3.1/3.4/3.8?

Original coolant? Ever flushed?

Your bleeder could be plugged.....

Surprised a P0128 is not setting.....

They only made this car with 3.8 engine.
Coolant that is used is dex cool(I heard a lot of bad words about it). Not sure about flush.
There is not codes on dash board and car is like that for more than a month.