hi, i have a 90 Chevy K1500 with a 350 and auto trans that is geting hot only when the ac is on and im sitting still, the motor has about 65000 miles on it as does the water pump, the radiator is new, the clutch fan is new and i have a 160 thermostat in it (had a 180 and didint help goin to the 160). temp runs 160-170 on the road and gets up to 210 siting. with the ac off the temp runs 160-170 at a idle. Any ideas?

 

You could add an electric fan to help push cool air through the radiator but I wouldn't worry too much, you aren't running hot. If you see it start creeping up higher then there might be an issue but 210 at a standstill is fine. It runs warmer because there is more of a load on it and being that you're not moving, the engine isn't getting airflow pushed through the radiator.

 

Also, running 160-170 while cruising is damn good. It's the nature of older clutch fan systems to run a little warmer when around in traffic.

 

Thank you! I tryed a electric fan already and it didnt help. Im not sure if it will get hotter than 210 cause i cut the ac off when it gets up there. I will check it today and see if it gets hotter than 210.

 

Did you have the electric fan outside pushing in ? I've known a few people who used the double fan setup off of an older Jeep Cherokee to push and it worked pretty well.

 

Yeah and didnt help anything lol Im gonna try a new water pump just to eliminate it and if that dont help, the only other thing i can think of is a problem in the motor (head gasket, cracked head etc.). i had a mis about a month ago when i would first start it and i changed plug and the #6 plug was wet and i noticed today it missed for about 20 sec when i started it so the plug is trying to foul again.

 

As i figured the water pump didnt help much. It idles at 205 now lol

 

Are you sure that you just don't have a bad temperature sensor?

 

Yeah i changed the temp sensor and then put in a machanical guage.

 

I had an over-heating problem on my 1990 suburban 454. I battled it for a couple of years changing everything the coolant touched (radiator, pump, thermostat, etc..), sometimes even change the item twice. Finally started taking the car to dealer, who was useless, as they said you need new exhaust components. So I changed them with no improvement.
As a last resort a friend suggested his mechanic he swears by. He diagnosed that the bearings on the distributor shaft were worn-out. Amazing! He mentioned that some of the plugs were firing as much as 10 degrees off! When I picked up the vehicle he worned me to be easy on the peddle because it's got a lot more power than I was use to. Duhh!! made a big difference, as I was not use to the way it was when I bought it new.
The particulars... at the time I started over-heating it was about 13 years old with 90K miles, I tow a travel trailer about 10-20% of all miles driven, and I have been very meticulous about the care of the vehicle. This distributor shaft bearing issue was something I'd never heard of, but he showed me the old parts and yep the bearings were worn down to nothing. They are a bronze type of bushing.

Good luck, I know how frustrating this can be. Oh... another this I did afterward was put in a Griffin Aluminum radiator. wonderful!!!