1999 Pontiac GTP heat/cool air same time

[George Foote]

Hi All,

I'm a first timer here.

I need some assistance in determining what's going on with my vehicle.

Back ground - 1999 Grand Prix GTP, 54K miles, 3.8 engine, supercharged
on 4/2003 (43K miles) cooling system was flushed, thermostate (180 deg) and water pump were replaced. Dexcool was reinstalled. ($600 bucks)

Recently, with the colded weather in Maryland .. I've used my heated.
The results of getting heat are mixed. From the driver side - the dash air vents and defoster blow out warm air, not hot but a good warm air . From the passenger side, its cool to cold air .... almost at times the temperature of the outside air. The variuos dash switches .. fan speed .. temperature selection and dual passenger selection all seem to respond okay.

Could the force of the flush locked any internal cooling system doors to an open position?
Could the the control panel .. an electrical problem ... be at the root of all this?

Whatever it is .. how much of a cost would I expect to see?

Thanks,
George

[paul1965]

From what I know understand about dual zone climate control vehicles, the blend door is the only thing that controls the temperature to both driver and passenger. If that is the case, it is impossible that the work you had done caused the problem (especially if it was not a pre-existing condition). More than likely, there is a large air pocket within the cooling system. There should be a small bleeder valve that can be opened to purge any air from the system. To properly bleed the air, the engine should be cool and not running. Crack the bleeder screw open, then add coolant to the radiator or resevoir. As the force of the coolant goes in, it purges the air from the system.

[Rocketboy]

Your symptoms sound similar to what I am experiencing with my 1999 GTP with 53K miles. This topic was also discussed in the below thread.

http://www.automotiveforums.com/vbul...d.php?t=162147

[George Foote]

Thanks guys for your replies.

Paul .. from your information it sounds like a good "burp" would fix it. It also sounds like the dealer might have failed to bleed the system after it was flushed .. do you agree?

Rocketboy ... sounds like we've got identical problems. Was your cooling system flushed recently too?

Thanks,
George

Now I'm wondering .... Maybe because the coolant system contains an air bubble... this could explain why my dash temperature guage is so active. It goes from 108ish to 200ish always. The radiator fan kicks in and lowers the temperature alright but, it just moves too much for my liking. My 2000 Jimmy temperature reading goes up to 190ish and never moves during my travels.
Paul .. do you think that an air bubble could cause this guage movement?

[paul1965]

An air pocket in the cooling system will cause the cooling fans and guage to react differently. The sending unit is designed to be surrounded by liquid, not air, so it's going to make it act erratically. Get the system bled and see how it works. It may or may not cure your problem with the temperature control, but should take care of the gauge problem.

[George Foote]

Thanks for your reply Paul.

I'll get with my dealer, set up an appointment and see what happens ... I'll FYI you when its resolved ... I mean paid for.

George

[Rocketboy]

No maintenance has been done to my cooling system, or the rest of my car for that matter outside of regular oil changes and tire rotations. I have had no problems up until now.

Like you had stated, let us know what you find out.

[kilroypr]

Let me tell you something, Paul is correct. The only thing that would control your car temp is inside the dash itself not the cooling system and if the dealer charged $600.00 and did not bleed the system you have to wonder if it was worth it. When you have air on the cooling system excesive presure is excerted on hoses and components that could cause a leak. Erratic temp readings could be caused from such readings and even fuel economy could be affected since the PCM(ECU) uses the temp reading with other sensors to control air/fuel mixture. So definetly you are correct, they should doublecheck your car since you payed then already a lot of money

[Ripn12s]

There is a bleeder valve on the top of the Tstat housing. Run the car up to temp, use screwdriver to open valve and wait for sign of coolant escaping. Close valve when you see coolant.

Im sure your other problem is somewhere in the dash.

[George Foote]

Update ...

Ah warm .. no hot air everywhere.

Here's what the dealer did ...
Complete cooling system check and found a defective "heat door actuator" (pn # 16163982).

Replaced the previously added (service from 3/31/2003) Dexcool with new Dexcool.

Test drove it for some 40 miles for verification of excessive dash temperature movement .. .... they too noticed the excessive movement and corrected it by repeatively bleeding the system. The temperature guage was moving some 15+ deg's on a normal drive ... coming home from the dealer today... some 12 miles .. it remained steady at 190 deg.
and the heat was WOW!

Here's what I did .. paid a bill for $439 (almost a 50-50 ..parts and labor)

Thanks all for your input... have a good one.

George

[George Foote]

Update ....

The temperature guage needle once again is moving from 190 to 205 deg's. It seems to move the most during the first few miles of warming up. Its rather uneasy watching the guage go up and up .. and hoping it stops .. and feeling releaved when it drops back to 160 deg and remains somewhat steady at 185-190. I had a 1991 Pontiac which did something similar to this .. except one day the needle continued to move until it overheated.
Well, I called the dealer .. see what happens now .. I'll keep all posted of the next episodes result.

[kilroypr]

Well looks like something related to the cooling system. What did they said about the water pump?

[George Foote]

Nothing said about the water pump yet .. it was replaced about 12K/one year ago.

Question for Rocketboy .... What does your temperature guage do during a normal drive? Does it move? Is it steady? If so, what temperature? My moves from 185 ish to 205 ish. Not like a yo-yo .. most of the time its at 185 ish ... then it seems that under load conditions it begins to climb gradually up to 205 ish then drops back.

Thanks,
George

[Rocketboy]

Honestely, I have never paid attention. I will watch this weekend.

[George Foote]

Well here's the latest .. kinda.

Friday it was back to the dealer. I spoke with the shop manager .. I felt like it was a good discussion.

From just a week ago when they reflushed the cooling (which was also done a year ago) it had signs of that rusty dexcool appearance. If this happens it a week .. what the crap happens it 1-2 years??

They now want to do an "old time flush" .. not totally sure what that means .. but, it sounds more like the way it should be done .. flushing it out with water until it runs clear... then refiling it with coolant`.
So, next week the car goes in for this. I'll update.

A few other comments about this meeting ....No hassile from the dealer.... has offered a loaner car too .. and an "off the record" statement was made ..."if it was me, I'd replace the dexcool with that green stuf... plus. if you don't replace the dexcool ...then flush the system like you would the green stuff .. every 2 years".
This I've heard and read about too. Maybe someday I will but, for now I'll let them do their flushes and make my case for me.

Thanks Rocketboy .. let us know what you see with that guage.