1999 Pontiac GTP heat/cool air same time

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

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.

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/vbulletin/showthread.php?t=162147

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?

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.

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

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.

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

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.

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

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.

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

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

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

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.

Well the only times that I have seen my needle climbing is under twisty and climby roads at the center of the island and it climbs a little and then back and keeps like that untiil a decent straight comes along where it gets steady. I have never seen rust on dexcool on my GP, even I replaced the green stuff with it on my Z34 and flush it ever 3/4 years and comes relatively clean and no rust at all. That is really not normal. I never have seen anything like what you comment here, and if the shop knows what they are doing they are supposed to flush the cooling system and make sure the car behaves as expected before turning it to you. Definetly I want to see how this turns out.

Not much of an update yet to relate ... more FYI.
This week it was "correctly" reflushed. It seems that the tech which initially flushed it wasn't totally up on how to do it. That's scarry! Well that old fashion flush that I mentioned before .. it was either done with water then refilled with dexcool ... or it was just done right.

It was kinda busy when I picked up the car that evening .. I spoke to the shop manager (he actually flushed it this time) and he thought that the temperature guage wasn't moving that much .. but, agreed it moved and thought the supercharger might have something to do with that ...which I don't understand??? Furthermore, he strongly recommended a "2 year" flushing cycle going forward. (Sounds like GM with there dexcool, owners manuals, sale literature, customer service folks and the dealership are not on the same page!!! Gee, what happened to 5 years/150K miles.)

I also wanted to know about the return of the rusty/muddy looking dexcool appearance ... what if it returns? Well there was a "it might return" in his reply "because of the dexcool properties" ... sounds like a little smoke up my you know what. I don't want rusty coolant!!

He/we agreed to monitor the coolant system for the next few months and see what it looks like in the spring ... and to bring it back for a recheck.

FYI...
I also have anyone GM vehicle - a 2000 Jimmy with 46K on it. The heating system works great. The temperature guage gradually moves to 205 deg and remains steady. I've never had the coolant system flushed. This morning (cold engine) I decided to look a the recovery bottle and remove the radiator cap and look in. Here's what I found ..

1. Recovery bottle was empty (according to many of the web sites about dexcool problems ... this is one of the two areas to monitor)

2. Radiator cap (on outside rim) had dried dexcool (this is the second item to watch ... if the cap gets too contaminated .. it fails to seat/seal correctly)

3. No signs of overflow down the radiator side

4. Inside the radiator the coolant .. no the fluid ..was about an inch low. I stated "fluid" .. because what I could see was clear, not the good old dexcool color ..red/orange .. looked like water. Does dexcool separate from water??? I hope not!

5. The inside of the radiator was totally.... I mean totally clean. The inside looked like it was new. No rusty/muddy deposits.

This vehicle goes in for a flush next week ... I'm planning to have them replace the radiator cap, over fill the recovery bottle ... and oh yeah, have their best coolant system tech work on it. Since the coolant in this vehicle is 4 years old, deciding to flush the system "mileage early" (it has 46K miles) wasn't a difficult one to make.

Interesting comparison .. both GM ... both with dexcool.

I'll update this thread "if" or "if not" or "whenever" conditions on the Grand Prix cooling system change .. and even if nothing happens ... and also after that spring look see ... I'll still let you all know.

Sadly, I still forget to look at the temp gauge when I drive it. Keep in mind my wife normally drives this car.

Anyway, good news for me, for the time being anyway, my actuator has mysteriously starting working again and I have heat on both sides of the car! I am sure that having it go out, even only temporarily, is a sign of things to come. For the time being, I am not going to mess with it.

I’ll try to remember to look at the temp gauge this weekend, and report back.

If you can get your hands on a scan tool hook it up to the car and see what the PCM see's for temp when the needle starts jumping around on you..

Also have u replaced the temp sensor?? Maybe thats gong on you.

I had this problem and check this out! I have had the same exact symptoms and have been a mechanic for over 15 years an drecently found out what this was and GM may deny this although I got the info from some insiders I know. The problem is that Dexcool sucks! When Dexcool begins to break down it forms rusty, brown clumps that clog the radiator and heater core. Flushing will only solve the problem temporarily. I bet you knew this when the brown rust returned! The problem with your heat may be a clogged heater core. Quick check. At operating temp. feel the two heater core lines ( rubber hoses the enter the firewall
just right of center-passenger side.) When at operating temp, they should both be the same temp with the heat on. If not, coolant is not circulating. This stuff blocks everywhere. Have you taken off your radiator cap to find clumps of Dexcool there? Anyway my problem was solved when I flushed the systme of the Dexcool and began using the green antifreeze. No more problems case closed. I manage an automotive shop and not many know this, but the Dexcool was the problem. I got the info from a GM service manager I know a few years back when they began experiencing these problems. I bet GM will deny this. How else are they going to get cars into there shops that have 5 year 60 mile warranties? Dexcool is good for 100,000 miles? Warranty is up and the car is in the shop!

Guys thanks for you replies.

Rocketboy .... yeah, check that guage and tell us what happens.

Ripn12s ... No, the temp. sensor was not replaced/ or checked that I know of.

Theguru ... Yeah, good old Dexcool. Positively don't like it.

Ripin12s & Theguru ... as I understand it from the dealership .. a complete test of the cooling system was done. I'm not sure if the temp. sensor was checked but, I'm thinking that it would have been checked because I returned the car with this problem. Yes, the hose temp. check going in and out of the heater core was mentioned too. (I believe they used some kind of a hand held tool to see deg numbers).

Since my last input here, I sent a e-mail to Prestone requesting verification on whether or not GM vehicles are still using Dexcool. I read this on another web site.


From Prestone ......
The Prestone Extended Life Antifreeze contains our own patented formula that is not the same as the type that was factory filled in your vehicle. Prestone only became a supplier to GM in 2001. Depending on how extensive the rusty residue is the contaminants may continue to appear even after a cleaning and flushing is complete. A good cleaning, however, should remove a significant amount of the debris. The Prestone Extended Life Antifreeze is approved by GM for your vehicle.

Thank you.

Prestone

Until I recieved this from Prestone, I was very reluctant to consider any coolant switch. I would assume that the "Prestone Extended Life Antifreeze" is green and not a direct color match (reddish/orange) for Dexcool. If that rusty look reappears (no bets please ... I'm sure it will) .. I plan on taking Prestone's e-mail to the dealer and have them reflush and replace the Dexcool ... free.

Now, keep this in mind .. I have two GM vehicles .. the 1999 Pontiac GTP and a 2000 Jimmy. The Pontiac is the only one that the Dexcool has the rusty appearance. The Jimmy ... 46K miles ...(looking into the radiator) was like looking into a new car's radiator ... no rusty at all .... totally clean.


I'll keep U-all informed as to the condition of the last flush results, still now with Dexcool, and if the rust reappears .. and if its back to the dealer.

C-ya.