1989 1500 PU clutch fan???

[southerndesert]

Hi All,

New here and looking for some warm engine help. I have a 89 1500, with new 350 engine, trans, and most everything under the hood including a newly installed AC system (done at dealer) The trouble I am having is with the engine getting hot while sitting at a light or moving slowly. Now the truck has always run at 180 degrees up until the new AC was installed. Now it gets up as high as 230 degrees before I panic and shut it off (AC). I called the dealer and he says no big deal, but if it didn't do it with the old crappy growling AC unit, why now with the new one? Could it be the fan, can I test it somehow? Just a note it is 107 degrees here during the day now, but the truck always ran cool last year.

Thanks in advance, Bill

[curtis73]

My honest guess is that your old thermostat was stuck open. 230 degrees is quite normal for a hot engine. Don't panic until you the radiator boils over... and even then its not cause for panic since its operating as designed.

Engines prefer to run hot. DRIVERS prefer that they run cool. The problem may also have been the the old "growling" A/C didn't cool very well. Not cooling well means less heat at the condenser, which means less heat to the radiator.

The worst that happens at 230 degrees is an ignition retard and loss of power. Your oil is blissfully happy at that temperature since it is successfully evaporating contaminants. Your fan clutch may need to be replaced.

My guess is that your A/C is also a culprit for the increased heat. If you think about it, it is a heat displacement device. It takes heat from the cabin and deposits it in front of the radiator. The better it cools, the more heat it makes at the condenser.

230 is quite healthy. You are however (especially for a chevy since they lack cooling system refinement) asking the vehicle to do incredible feats. Its 107 outside, no moving air except an idling fan, A/C on full blast making 250 degrees at the condenser. The fan is pulling 107 degree air over a 250 degree condenser, and asking it to cool a 230 degree engine.

Two solutions; either kick it in to neutral and rev it slightly to get air moving while you're stopped, or install a couple 12" electric pusher fans ahead of the radiator to come on at 200-215 degrees and hotwired to be on when the A/C is on.

I've been in Chevys at highway speed in the desert where the fan clutch kicked in. That is ridiculous. If a cooling system can't cool itself with 70-mph air and 15% throttle, then it is completely inadequate, as most of the late model GMs are in the cooling area. Better radiator, supplemental cooling fans, and airflow are the keys. Whatever you do, do not reduce your T-stat temp rating. That will just open it sooner and postpone overheating by 30-40 seconds. Once the stat is open, overheating is caused by more heat in than can be taken out. Even if you remove the stat, it won't help overheating in this case. You'll still overheat in summer and have little or no cabin heat in the winter.