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Pontiac Repair/car trying to overhead when idling


QUESTION: I have a 1990 Pontiac Grand Prix that when it is idling tries to overheat unless I put in neutral and rev motor up higher and can turn on the heater and after a minute or two it will start to cool off. I pick my grandbaby up from kindergarten and the line is quite long and I have to do this to keep it from overheating. It also does it if I am at a light too long or contruction work or anywhere where it is in idle mode. It is frustrating since it never ever even tries to do that at any other time. It has a new thermostat so the temp stays down right at all other times. Please help me so I do not have to do this when I am waiting for him. It is a 3.1L engine. It gets to the point of almost red and am afraid that it will overheat. Thank you.

ANSWER: Hi trudy:

well first off make sure when the dar is cold that the radiator and over flow are full if not there is a leak. next thing to check is to see if the cooling fans run. if the car is equipped with ac (and it still works) start the car up turn on the a/c and see if after a minute or so if the fan turns on. if so the fans work. if not there is an issue with the cooling fan. when it gets warm/hot see if the fans turn on if so then you have to look into maybe a mechanical issue like a head gasket starting to leak. again if the fans don;t run that is the root ciause of the issue. Hope that hekps you out. good luck :-)

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QUESTION: My husband says the cooling fan comes on when the ac is running but not when it tries to get hot and is idling. Probably fans then but why would they run with the ac and not when idling? Thank you. Oh and everything is full.

Ok here are a few more questions. when the fans are running do you feel the air moving across the grill going into the engine compartment? The air flow could be blocked between the radiator and the condenser for the a/c. dirt dust tree polin etx plugs ups the fins and the air flow is cut for the fans NOT turning on when it's hot the engine temp usually has to be upwards of 220 degrees or so for the low speed fan to turn on and 230 or so for the hi speed fan to run. so if it's getting that how and the fans are not turning on the engine computer controls the fans it could be that as the issue. The only way to tell is with a scna tool and see what the engine temp is reading and if the computer is commanding the fans(S) or or not.  

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Todd Puccio


General auto repair,electrical issues,driveability issues,anti-lock brakes,SIR systems,HVAC,engine performance,Gm specific. I have worked at my current dealership since the 1990 model year anything much older than that I have limited exposure to. I do not have very much transmission experience so those question you may want to ask of another expert. When you send me a question let me know the exact make/model/engine and year for the car or suv you have it makes it easier to answer the questions that way. If your happy with the answer I gave you please feel free to Donate. This is a free service to you and I am not compensated at all by this web site. I have 22 years of experience to share with you and my knowledge wasn't free to me. I had to pay for my education.


Experience in the area: I have been a technician in GM dealerships for over 22 years and I am a ASE master technician. I work at a Buick and GMC truck store Previously I worked at a Pontiac GMC store for 18 years. I Served a a lead technician when dealership was on a team system. I just recently moved to a Buick,Hummer,Saab Store when my franchise was purchased by this dealership. Organizations: ASE master technician


Education/Credentials:High school diploma,2 year vocational school degree 2 year college degree. Associates degree in applied sciences (auto technology)Awards and Honors: GMC master technician

Awards and Honors
Master GMC truck technician Master ASE technician in 9 categories

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