03 Grand Prix - where's the heat????

[Randall Carlisle]

Hey, been lurking thru the forum for better part of day. Nice forum. My wife has an 03 GP GT.

I am driving it this week and it has no heat. So from what I've read - i either need to flush heater core and bleed, or need actuator doors. This morning I had no heat. Temp gauge reading 180 or so, but would go up to 200ish at stoplights and then drop back down when moving again. I can hear the compressor kick in when I turn the fan on when it's on defroster setting. Both sides seem to be equally cold when turned to full hot. And even colder when on defroster. Will check heater hoses when I get in this evening. It does have coolant but was a tad low. Dexcool 50/50 added.

There are no fuses for blend doors, correct? And the blend door actuator is what is controlling the amount of hot/cold, correct? These are electrically operated, not vacuum, from what I have read. Fan works in every position, and it changes from defroster to vents to floor with no problem.

Only other issue I have with the car are those uncomfortably shaped headrests...

My first car was a 73 GP. $300 and was stout as an ox.

Randy

 

[Scottydoggs]

when the cars warmed up, carefully check to see if both heater hoses are hot. if they are cold, flush the core.

 

[loopy smurf]

Has the heater core been bypassed? I had a car once where the previous owner bypassed the heater core instead of fixing it when it went out. Not sure if this is your first winter with this car, or what, but that just popped into my head.

 

[Randall Carlisle]

Wife bought car new in 03 or 04. It was last 03 they had - not sure, but we've had the car since beginning. So the heater hasn't been intentionally bypassed.

Here's what I found last night. I drove home - 30 miles. Had heat on occasion, if I left it off, then turned it on - like it was "saving up". Soon as I turned car off, popped hood and checked htr hoses, both warm but not hot, as well as upper hose. They all felt about the same to my non-calibrated hand. upper rad hose was squishy, would gurgle back thru expansion tank.


After dinner, went back out and started car to let it warm. And warm. And warm. Would not get to 185, which by my guess would be the big mark btw 160 and 210. So then I sat there with foot on pedal, "idling" at 2500 or so, which finally got it above the 185 mark, but never to the 210. The engine fans came on and I could make it produce some heat inside. upper hose still soft, squeezable, not really hot to touch, with car off or on.


Played with heat sliders and can hear an audible change in both with fan on. So I think the blend doors are working


So my theory is that it has either or both: air in the system and maybe a stuck open thermostat. The coolant is not warming enough to heat the heater core? My uncle, who is pretty mechanical, thought the same thing.


May try to bleed it out this evening, and check that. I don't have my manual here, so am kinda dependent on you guys and net for instructions.


Thanks for the help.
Randy

 

[Fivefingerdeathpunch]

I would say a coolant change and new thermostat would fix this issue.

On my car that first big mark after 160º is 195º, then it goes 210º.

I would say there is air in the system or the thermo is getting stuck and not allowing the heat to build up.

To bleed the cooling system the car needs to be at operation temp and then open the bleeder ontop of the thermostat housing with a screw driver or 7mm? socket and turn it about 1-2 turns until you see a little bit of air/coolant being spit out. Wait until its a steady coolant stream and close it up.

You can also hold the rpms at say 2,000 and crack it open for 3-4 seconds at a time and close it. Do that over and over for about 1 min and that can get the air out aswell.