Whats up everyone, I have searched the message boards and can't find this on, but anyways, I have an 89 iroc with the 5.7 tpi engine. I just recharged my AC and the car is now overheating whenever the ac is on. Car has a brand new radiator, 2 brand new fans that run all the time, new 160 degree thermostat, hypertech chip, and the air dam and deflector are there and in good condition. When I don't run the AC the car never pops above 160, whether in traffic or on the highway when I turn on the AC it slowly starts to rise until it reaches upwards of 260 degrees. Any help you can give will be much appreciated. Ok and just in case you were wondering I am running the correct mixture of coolant. I am a trained and licensed ac repairman so the ac system was charged properly.

 

Could be any number of things. Having the AC on just puts more load on the cooling system by heating up the condenser(in front of the radiator) Your cooling system is capable of cooling the engine, but not the engine and AC. How is the water pump? Hoses OK? Ignition timing? and all the other stuff that affects the cooling of your car?

 

Car has new pump, radiator, hoses, and 160 degree thermostat. Timing is 10 degrees advance at idle.

 

I have the same problem on my 91 Z28. It drives me crazy. It just slowly gets hotter until i have to turn the AC off to cool it back down. I have also noticed that when i go above 80 on 90+ day is when i run into that problem, but on a 100+ day nothing I do helps it. I would love an aswer to that problem.

 

Yep thats what mine does but unlike yours it will still cool down to 160 when I turn the ac off, no matter what temp it is outside...

 

That is with the AC on. When it is off I have no problem keeping the car cool. I run 180 Thermastat and it runs at that on the highway no problem.

 

I dont know much about the a/c and cooling but have you guys checked to see if the condensor is in tip top shape and to see if theres anything blocking it.

 

I have cleaned it out before. It was not that bad to begin with, but it didn't make any difference for me. I am going to try a high flow water pump next and see if that will help.

 

Heres a dumb question, have u checked to see if the fans are running when the a/c gets turned on??, i know u said that u wired the fans to be on all the time but they could turn off some how. I dont know much though but just a try. I cant really think of anything else, its very weird that ur car runs so cool withour the a/c on and just by turning the air on u overheat

 

Well, I tryed a suggestion that I read on this board. As you know hot coolent is always flowing through the heater core, at least it is on my 84 Z28. That in its self is not a real big problem but were the coolent from the heater core returns to is. The coolent source for the heater core comes from the front of the intake manifold. This is were the hottest coolent is returning to the top of the rad. This makes sense because you would want the hottest coolent for the heater core. But its that hot coolent (cooled some) from the heater core that returns to the water pump that is the problem. Coolent is also being sucked from the bottom of the rad. (cold side) and is being preheated by this hot coolent that is returning to the water pump. I installed a heater control valve from a Monte Carlo and shut off that hot coolent to the water pump. This helped some but if its 90+* I still have to shut off the A/C in stop & go traffic. It does take about 15 min longer though to reach 260*. My next mod is to put that plate (that I have had for years) on the water pump impeller. To be continued !!!!

Auggie

 

I USED TO HAVE THAT PROBLEM UNTIL I MODIFIED THE AREA WHERE THE K&n FILTER GOES. YOU NEED TO GET MORE AIRFLOW GOING SO IT COOLS THE ENGINE. WHEN YOU STOP YOU ARE SLOWING THE COOLING PROCESS. TRY CUTTING OUT THE AREA UNDER THE FILTERS SO YOU CAN GET A BREEZE IN THERE.

AGGIEz28
91 MAROON Z28