I have an 86 Trans Am and my car is starting to overheat. I put a new radiator and fan motor in last december and since summer hit it has started to run hot. The replacement radiator was smaller than the stocker so that maybe the problem. By the way, i have the fan operated by a switch and it runs all the time. With the AC on it naturally runs hotter but it didnt last summer with the old radiator and fan motor. The polarity on the motor is right and it is pulling air and not pushing. Any ideas?

 

what kinda mixture of coolant are you running?

what type of thermostat?

did u replace the rad cap lately?

hows the air dam?

 

I had the stock 195 in it but changed to a 160 but saw no change. the coolant is about 60/40 with more water. i did this cuz my mechanic told me to and he happens to be my dad but he hates my car. the cap was tested not too long ago. im sure it is in a flow problem. last summer that car ran about 160 regardless on the outside temp. this was with the fan running with the ignition switch. when i replaced the fan motor i ran it to a toggle switch in the car. i run it all the time and its ok on the temp as long as im not in stop and go traffic. in traffic it goes up and i know its gonna do that but the fan is running and once it gets up to around 210 it wont stop. With the AC on it gets worse and heats up real fast. im sure im gonna have to have a fan that pulls more CFM and prolly a bigger radiator.

 

why did u get a smaller rad., you should of at least gotten the stock replacement?

it could be your waterpump?
you also might have a clog somewhere around the heater core, i would bypass that for a while and see if it changes anything..

 

I bought the radiator because they told me it was a factory replacement. the heater core has been bypassed for about 3 months and showing no change. the new radiator is thinner so the fan sits farther away from the radiator. i might add that the new radiator is aluminum as the old was copper. aluminum has better heat transfer but it is smaller. so im stuck with a problem of what do i replace first. the waterpump is a little over a year old so i hope it isnt that. ill prolly start with the fan and buy a bigger one. my car is equipped with AC but only has a single fan.

 

yeah i would upgrade to dual fans first, or a faster single fan.

 

TATPI,
You didn't mention your air dam. Is it in place? your symptoms sound very much like the engine isn't getting enough airflow at high speeds. The fans can't pull enough air for the heat generated at high speeds so the engine depends on air scooped up by the dam. Also, it's better to have it angled forward, not backwards. In a worst case scenerio, if the air dam is missing or angled too far backwards, the airflow under the car could be pulling air backwards through the radiator, fighting the fan's pull and making the fans even less effective.
Having the AC on will always make the car run a little warmer because it puts more strain on the engine.
Also, see what you can do to reduce the gap between the radiator and fan. The fan could be pulling less air through the radiator because of this.
The main thing to fix is the air dam, do that first.

 

my problem is not at high speeds. once the car is moving it is fine and the temp drops like it should. and the airdam is intact and is not angled backwards.