cooling issues, fans wont start


Asked by May 09, 2012 at 07:03 AM about the Pontiac Grand Prix

Question type: Maintenance & Repair

98 grand prix,3.8,. had a blown head gasket, removed the heads had a valve job done, and replaced all gaskets involved with replacing the heads. also replaced radiator, water pump, tstat, ect sensor, and antifreeze.went to start car, fired right up, but no fans come on, gauge climbs fast to 200+ degrees, nothing no fans, i unplugged the ect and both fans come on, so fans and relays ok,it doesnt boil over though, i would think it should, previous owner removed heater core, also my ground on battery gets very hot, please i need some help,  

8 Answers

check for air pocket , if the sensor isn't sitting in anti freeze it won't work. when the engine is cold ,warm it up with the radiator cap off until thermostat opens ,if the anti freeze level drops ,top it off & put cap on . if you see bubbles that don't stop , good chance you have a cracked head, did you have the heads pressure tested?


thanks, but yes i had the heads pressure checked and complete valve job,im pretty sure i got all the air out of the system, i have ran the car with the cap off and i have top it off, i can feel when the t-stat opens up cause the radiator goes from cool to warm. but the temp gage spikes up at 240+ degrees in less than 5 min. im pretty sure the ect sensor is sitting in antifreeze, i took an ohms reading at the ect, when cold it was 2300+ ohms, than another reading when engine was warmed up 230+ohms, after reading some other sites on t/s the sensor it reads out as working fine, i also checked all my grounds, I just cant c why the fans wont come on, also when the gage is spiking at 240+ degrees, it never once boils over and i can put my hand on the radiator cap, is there any way i can wire the fan relays to work when i turn ignition on, in other words by pass the pcm, so i can drive this thing,

3 out of 3 people think this is helpful.

If your gauge is climbing that fast there is a restriction somewhere or blockage. Can you see the coolant flow in the reservoir and you said you have bleed system correct?

1 out of 1 people think this is helpful.

i'm wondering if there is a electrical problem. the engine shouldn't get that hot in 5 minutes. all 7 of my 3.8 L engines never did reach 240 that quick. only if there was air in the system.


I've got a 1999 3.8 with 179,xxx and when I drove for 10 mins or longer it would shut off as I was driving . Later I found that it was a bad ignition module , replaced that . Now it stills shuts off at around 200deg , so then I replaced the thermostat now I can drive about 15 mins , then shuts off . Why ? Everywhere I go the same answer , it could be many many things . I need the answer to be narrowed down a little more than that . But , in the beginning , I also put some bars stop leak in it as well cause it leaked anti freeze but I couldn't find out where . So I don't know if that hurt anything or not . I need some help . Auto stores most likely just want as much money as possible from you , and , my Service Engine Soon light just now came on .

1 out of 1 people think this is helpful.

unplug your TEMP SENSOR and your fans will run when the engine is running and stop when you shut the engine off . However your problem lies in the FUSE BOX in behind the GLOVEBOX there is a fuse for your fans in there as well .

8 out of 8 people think this is helpful.

AIR POCKET in cooling system has MULTIPLE SYMPTOMS from a bouncing temp hand , no heat from vents , can cause overheating in a hurry , BLEED OUT from the TOP OF THERMOSTAT HOUSING (let engine run for 3-5 minutes then shut off ) 7mm just loosen BLEEEDER until you hear the air spewing out and close it when the air stops , start the car back up and REPEAT until all that comes out of bleeder is antifreeze( can take 30 minutes - 1 hour to complete in extreme cases )

3 out of 3 people think this is helpful.

water pump?

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