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

[rcarlisle]

I have quite a bunch of driving each week and have been riding my motorcycle. But this week, it's supposed to be cold and I borrowed the wife's 03 GP GT, 3800 ser II. Coming down last night to where I stay during the week, I didn't need the heat. But this morning I did and it's not there. My daughter had mentioned that it didn't seem warm enough for her, but she stays cold, so I didn't think about it, other than I needed to check it. Well, I did. And she's right, no heat.

Here's what I do have: 48 degrees this morning. temp gauge reading 170 ish at normal running speed., will increase to 185, or even 200 at stoplight. So I checked coolant and added some, just to make sure. Dexcool. No change. My thought was if it were almost completely out, it wouldn't ever show warm. coolant in radiator, too, up to neck. When i turn on defroster, I can hear motor lug down, so I assume the compressor is kicking in as it should. Can feel no discernible heat with sliders all the way up. Just cold air. Colder when defroster on (compressor).

What do I check next? Is there one of those actuator doors that go bad in other cars? how to access?

I thought it would be warmer to drive car - I may be wrong. I at least have heated grips and seat on bike.

Thanks
Randy

[00Beast]

Crack the bleeder with the engine hot (be careful, and preferably have the nose of the car angled up) and make sure it's a stream of fluid that comes out, to make sure the system is bled. If there's an air bubble, it's gonna be in the heater core.

[Archon]

Make sure that your coolant to water ratio is not too high. If it is, the coolant is not as efficient at removing heat from the engine, and will also affect the amount of heat that you get from the heater.

Also, feel the heater hoses going to the heater core. Are they at least quite warm? If not, then the heater core likely has air in it as Beast mentioned. If one of the hoses is a lot warmer than the other, then the heater core is likely plugged. Back flushing it should help that.

[rcarlisle]

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 fans came on and I could make it produce some heat inside. upper hose still soft, squeezable, not really hot to touch.

Played with heat sliders and can hear an audible change in both with fan on.

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, check that. Where I am I don;t thing there is a hill within 50 miles to get nose up...but will check it out. I don't have my manual here, so am kinda dependent on you guys and net for instructions.

Thanks for the help.
Randy

[Archon]

Do you have ramps, or a jack and jack stands to raise the front end?

[rcarlisle]

Yeah can probably use those here at work. May try it tonight or one evening if I can get the parts together. can the lower rad hose be changed easily? May as well change hoses too while I'm at it. Added insurance.

Randy