All right...I know this is for Ford trucks, and since I am a proud owner of a 1989 F250, I thought I'd ask a question about a general overheating problem...

My wife's Pontiac Grand Prix overheated tonight...it didn't boil over, but it got up as high as the needle would go and the light came on...I pulled over and the needle started coming back down... I took off again and the needle started to climb...I had the defroster turned on high and noticed the air coming out had cooled down a lot. then it started blowing warm again a minute or so later. When I pulled in at home, I left the car running and got the shoplight out to look the car over. The hoses were pressurized, nothing was leaking. the needle stopped just short of the red zone on the guage. I got in the car, revved it a little...the needle dropped then...a lot...back to almost normal. When I stopped revving, she started to climb.

Thermostat? I would think it's the water pump...least I hope not...

Any input will be greatly appreciated!

Thanks!
Phil

 

I had a similar problem on my truck. At idle the temps would go up. But if i was moving I could keep enough air flowing through the radiator and bring the temps down. My problem turned out to be two problems. The thermostat rusted itself shut, and the water pump bearing went out taking the pump with it. I was suprised to find out the my 300 can run air cooled. Hopefully your problem isn't bad. Sounds like you are not getting much water flow. I would start at the thermostat. One tip before I leave though. If you find yourself overheting, I usually open all my windows and turn the heater on full blast. It has saved me when I go offroading a couple times when I splash up enough mud to clog the radiator. hope this helps you

 

Toecutter,

Does the electric fan come on?

Jr has a good idea with the water pump.

It could be thermostat. I had one that was stuck barely open. Enough that at idle it would be okay, but when I was in traffic and going up the mountain, the darn thing would get hot. It never boiled over, but it sure got close.

My opinion is to start with the cheap parts first, i.e. thermostat.

You probably know this but you can heat a pan of water to boiling and drop the stat in it and it should open way up. There should be about 1/8" opening around the spring. If not, it's bad. And it should be easy to remove/replace.

 

I picked up a new thermostat for it this morning...haven't put it in yet. I replaced the water pump this morning...got to looking and noticed there was some water coming out of the weep hole. I'm starting to think it is the thermostat though...I don't think it's opening up all the way like J.R. said...I think it's enough as long as I'm moving and the water pump is pushing the water through, but then when it cuts to idle, there's not enough force to push enough water through. Like I said, when I rev it the guage comes down...soon as I let it idle, it starts going up. As far as the fans go, there's two of them...one was running last night, the other didn't kick in....may not unless it's really needed...

The thermostat oughta be real fun...they designed the exhaust from the front to run right in front of the housing so it's a royal PITA to get at....

Thanks for the advice!
Phil

 

Anytime Phil.

 

Yep...looks like that was the problem...I pulled it...after snapping the upper bolt on the housing, I was able to pull it out...looks like it was hanging up on itself so it was letting a little coolant through, but nowhere near enough. Now get to have fun drilling the rest of the upper bolt out and retapping...what fun.

Damn GM's...

Thanks again!
Phil

 

Aaaah...it never ends....must be an air pocket in there somewhere now. It travels around...first I get hot air and the heater is putting out good, then it the guage climbs up and I get cold air....step on it and the bubble goes somewhere else and I get heat again....I've bled a lot of air out, but I obviously haven't got it all....

Any suggestions on how to get it out?

Thanks
Phil

 

Try this. Drive around and let the car warm up. Then jack up the front end of the car to make the radiator cap the highest point in the cooling system. Then start the car back up and remove the radiator cap. Whatever air is in there should come out. Let us know how it turns out.

edit: run the heater while you are at it just to make sure you have water flow through your heater core.

 

Heh...well, looks like I've got a blown head gasket...I've got white foam on the oil fill cap, although the oil on the dipstick isn't foamy. The exhaust sounds like it's "chugging" and there's quite a bit of moisture coming out of the exhaust...I've had head gaskets go before, and they always seemed to put out a lot of fog...I don't ever remember it making the chugging noise at idle, but I've only had the car a month and a half...I think the used car dealership seen me coming. Other thing I noticed was there were a lot of bubbles coming up through the radiator when I was filling it as it was running. Problem there was, it wasn't taking anymore anitfreeze...so I let it warm up...added more anitfreeze once it was up to temp, and then it took...then there were no bubbles coming out of the radiator, but if you grabbed the upper hose it felt like there was air bubble going through it...then the temp kept climbing...around 260 I'd guess. Another clue was when I pulled the intake butterfly off there was a wet goo on the back of it...I'm assuming up through the blowby....I just hope I don't have a crack somewhere....parts are easy to get, but it's gonna be a royal pain....


Let me know what you guys think...I'm probably gonna start into it pretty soon...

Thanks
Phil

"I knew I shoulda bought that Ford Taurus I looked at... :-)"

 

Bad deal. I would agree it's a blown head gasket. Hope that's all that it is.

 

I've got a 92 Regal that has a coolant bleeder located at a high point on the engine. Look and see if you've got it (prolly do, GP is basically same thing) and open that little brass bleeder to expel air. In their infinite wizdom, what will GM come up with next?

 

Definitely a head gasket...material between water jacket and the metal ring was blown out on the number 2 cylinder. Amazing how a little steam can clean a piston and combustion chamber up.... I'm just glad it wasn't worse. Not an easy job pulling the heads off of one of these motors...royal PITA...not hard, just time consuming...so much stuff to take off....so much to disconnect...

Oh well, it's going together good...hopefully I can fire it up tomorrow.


Thanks for the input!
Phil

 

IT'S ALIVE!!! Got it fired up around 1:30 yesterday afternoon...

I've had this car 2 months and it's been nothing but a headache... I think it's time to sell it...

Let someone else deal with it...

Thanks for the help!

Later
Phil

 

On the topic of thermostat testing, I would suggest the following. Preheat water to just below the design temp of the the thermostat. Put it in the water as you gradually raise the temp. Note that the thermometer cannot rest on the bottom of the pan. At the design temp the unit should begin to open. The last two that went bad on me were opening 10-15 degrees late. By doing this test I was sure that the problem had been the thermostat and not something more serious. Good luck with that chibby, John

 

Eventually you will work through the problems and have a reasonably reliable car. If you bought another used vehicle would you necessarily come out better?