closeshave2

So I bought a '96 GT a couple of weeks ago to use as my daily driver. I've been struggling with an overheating problem ever since. I've replaced the thermostat, the water pump and the radiator at this point. The car seems to run perfect, with the temp gauge straight up, until I turn on the A/C. With the A/C on, the temp gauge slowly starts to climb even if I'm doing 60mph down the highway! Once the gauge gets high enough to make me uncomfortable, I'll turn the A/C off and the temp gauge returns to normal.

I'm baffled by this. I've checked the fan and it appears to come on when it should. The thermostat appears to be functioning as it should since the upper radiator hose gets hot. Can anybody offer up a suggestion as to what could cause this type of behavior?

Thanks in advance.

closeshave2

TTT

Any suggestions?

jlg32281

Where are you? How hot is it? What anti-freeze mixture are you running? Drain your coolant, and run a 90% distilled water, 10% anti-freeze, and an additive (water wetter of similar). You can also put in a lower temp thermostat. I run this setup with a 160 thermostat.

closeshave2

I'm in Texas. With temperatures over 100 degrees for the past two months, driving without the A/C can be uncomfortable! My wife won't even ride in the car...

I'm running 50/50 coolant with Water Wetter. The thermostat is 195. I was considering changing to a 180 thermostat, but I don't think it will matter. The temp gauge is steadily straight up until I turn on the A/C.

Changing the coolant and/or the thermostat will surely make the car run cooler. But when I turn on the A/C, I suspect it will inevitably make the temp gauge start to climb just as it does now.

Or am I not understanding something?

closeshave2

TTT

Alright, so maybe running 90/10 coolant is worth trying. The only thing I'm concerned about is corrosion. Is 10% coolant enough to keep rust from being a problem?

Any thoughts?

Modular_Madness96

Try power washing the condensor maybe its just really dirty and slowing airflow?

ROB 98GT

I had that problem all the time with my 98. I had march pullies installed so switched back to the stockers and the problem went away!

powerfreak

Did you "burp" out the cooling system enough??? there might be some air trapped in there.

You can also get a tuner and program the fans to come on at a colder temp...can't hurt, being that your in texas.

jbors1

im new here, but dont most cars run hot with the A/C on?

03FstStngKB

Yeah most cars do run hotter than what would be considered the norm. Cars who's cooling system is not running at maximum efficiency like it's suppose to I suppose would compound an overheating issue though and I would think you would realize a general cooling problem w/o running the a/c in some situations.

Correct me if I am wrong but other than the compressor putting a good strain on the engine, the main reason why your temps run hotter is because of the basic application of how a/c works. You have a heat exchanger or condenser that is drawing hot air out your car and where that exchanger is located is right in front of the radiator. When the fan is pulling cooler air into the radiator it is also pulling the hot heat out the exchanger thru the radiator also. I am no a/c guru but I think that is basically the concept behind the warmer temps??