Running hot and No AC


Asked by Jun 06, 2016 at 11:27 PM about the 1999 Pontiac Grand Am 4 Dr SE Sedan

Question type: Maintenance & Repair

Baby (my 1999 Grand Am SE) has always been touchy when it is in the 80s.
We have always paid VERY close attention to her temp gauge. She had
routine  maintenance done today. (Back up lights fixed and her valve covers
tighten to stop a small leak) When I drove her home I noticed that she got
hot faster than usual, but settle in to her normal temp range. So I parked her
under her favorite shade tree. A few minutes ago after she had sit for 4
hours I went and started AC and her temp gauge went from 0 to
150 in a matter of seconds. (It usually takes driving her at 55mph for 10
miles for her to reach 150) Have I got a bad thermostat? Is it the AC not
working that is doing this? Do I need another new water pump (We are
pump number 4) Am I just being paranoid? Help.

4 Answers


Inspect the complete cooling system might be new RADIATOR time. 4 water pumps is a clue lots of debris in system. look for loose fins on the radiator and corrodes areas If you really like the vehicle replace the Radiator. 17 years, was good life for the old one.


Her radiator is fine...just had it checked. The only reason she has had 4 pumps...the first one cracked when she was ten, then the dealership put on the wrong one at that time, leading to a complete over haul of the the engine and pump #3. 4 came when her timing chain was replaced along with several hoses and her belts...which was 2 years ago. The only thing that has changed with her at all is the AC has stopped.


The AC not functioning will not effect the engine temperature. There is less load on the engine without a compressor working to compress refrigerant. UNLESS, its binding and the belt is slipping or burning (I think you would notice) I would expect water pump number 4, to still be Ok after only 2 years. which leaves the temp sending unit... after starting and displaying an almost instant 150 degrees sure doesn't behave like a t-stat, we all know it takes a while for an engine to come up to temperature not a few seconds! If you have a multimeter check the Resistance of the coolant sender / sensor unit..COLD 50-80deg 9400 Ohms.... HOT 180-220deg.175 Ohms.. IF resistance doesn't decrease as the coolant temperature rises replace this $15 sender / sensor. Regards


Thanks. I also wondered, could I have a belt pully that is not working?

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