Okay So I have a 1990 mustang GTwith the original 5.0 motor. I wanted to set the car up for drag racing so I took the 5-spd out and put in a C4 auto trans. Ever since I put the new trans in I've had nothing but heating problems. I've done many things to try to correct the problem.

FirstI started with putting a 160 thermostat in and buying an electric fan. That killed some heat, but not alot. I then purchased a new bigger radiator made of alumininum, and the car ran hotter. We then thought the car was not getting enough airflow so I custom made a grill for the car. This killed about 10 degrees, but when its humid out the car still runs at 230 degrees, and at idle it will get up 220 degrees.

I do have 4:10 gears which makes me run down the road at 3100 rpm @ 55mph. The trans cooler is mounted in front of the radiator, and car did run a little hot with the 5-spd. It ran about 210 in the hot summer, so I put the 160 thermostat in and that knocked it down to 180-190 degrees.

The only other thing I can come up with is the water pump is bad. I've ordered a new one and plan to put it in as soon as I get it. Please make any suggestions as to why my car is overheating?

 

i had the same problem on my '90 but with an a/c condensor in front of the radiator restricting airflow. i put a new clutch fan on it, took out my electric fans, and threw in a 160* thermo. that did the trick. also make sure you've gotten any air bubbles out of the radiator hoses. especially the top one.

 

water pump or head gaskets.....but first make sure the radiator cap is good = new = 16lbs cap..and make sure your gauge is accurate

 

Did, you take out your A/C condensor? And yes I did change the guages and bought brand new one's and I also have 16lb radiator cap. I'm only left with two options and that's the water pump and head gaskets. I just hope the water pump works.

 

make sure you are running the proper coolant/water mix. I have seen so many people screw that one up!

 

perhaps there is ALOT of crap stuck int eh fins of the radiator, take it out and hose it down.

 

Well, I don't think the water/coolant mix would make me overheat 40 degrees, and the radiator is brand new.

 

+1 on the air in the hoses as air captivation can screw with the thermostat. The other thing you might try is backflushing the engine. If you got crap in the coolant channels in the block, that can make a difference. Other than that, you've checked almost everything else.

 

wouldnt you notice poor idle quality if the head gaskets were bad?

 

I do not know the answer to that? It idles fine, it fluxuates on a cold start but i think its the idle air control