taken from gmtips.com
Common Reasons that F-Bodys Overheat
The first step in tackling a consistent overheating problem is to determine in what instance is your car overheating:
1. On the highway.
2. Normal traffic, city driving.
Overheating on the Highway– is a pretty sure bet that the air dam on the bottom of your car is damaged or gone. This scenario usually confuses us because we are use to a car cooling down at higher speeds and yet here we are overheating at 60 or 70 MPH. Especially in the Trans Ams and Firebirds, although it happens to Camaro’s also, our cars do not have a grille. Our fresh air supply has to come from somewhere. It comes from underneath our cars. We have a “scoop” called an airdam that scoops air up from the underneath and diverts it to our radiators and make no mistake IT IS ESSENTIAL. This air dam is easily torn off on curbs, etc. and the first step in diagnosing a overheating on the highway problem is make sure this piece is in tact. It is not very expensive from the dealer. Without this piece, at highway speeds, the airflow just bypasses the engine bay and scoops right out the back of our cars with no cooling effect whatsoever.
Overheating in General– is tackled in a little different approach. Providing you have made sure the air dam is in place we will follow a diagnostic sequence to try to determine where the problem is. YES, you could install a high volume waterpump, an aluminum desert radiator, lower fan switch, lower thermostat, and convert to dual fans (for single fan users) BUT, why not fix the problem first. Your car was designed to operate normally with the equipment it has and at one point in it’s life I’m sure it did. So we should repair before we modify.
Make sure you have no trouble codes. Code 15, Coolant Temp Sensor Bad, or Code 44, lean exhaust. Have you made any radical changes before your car went haywire? Headers? New Cam? Have you been having transmission troubles? Because if you have there may be nothing wrong with the stock cooling it just may no longer be able to keep up, in which case you will need to jump right to making modifications.
The engine has to be in proper tune. Especially timing. If the timing is off your car may overheat. If we are in tune with no major “heat producing” mods, our tranny is OK, and we have no trouble codes then lets check the following:
1. Obstructions to the radiator. Nothing like a giant Wal-Mart bag covering our radiator to decrease airflow. Check for leaves, cardboard, racoons, anything that might be blocking airflow.
2. Condition of the radiator – Are the fins straight or are they smashed closed. Straighten all fins. Depending on the age and visual condition of the radiator consider either replacing it or having it rebuilt. If you suspect radiator damage at least take it to a specialty shop and have it pressure tested.
3. Check Hose Condition – to make sure your hoses are not collasping under operating temps.
4. Check Thermostat – Unless you’re really sure just replace the thing. It’s cheap enough and chances are you need it.
5. Check the radiator cap – same as above, it’s cheap enough, when in doubt replace it. Operating the system “under pressure” is what raises the boiling temp within your system. If you’re losing pressure it will boil at a much lower temp.
6. On a cool engine – remove the radiator cap and watch for coolant circulation as your car warms up. Lack of circulation would indicate a bad water pump.
7. Everything Else – would include testing your antifreeze for the proper 50/50 mixture. Consider draining and flushing the system to rid it of contaminants (dispose of this highly toxic solution properly). Refill with fresh antifreeze and consider using distilled water instead of tap water. Check for any leaks. Check the interior for the sweet smell of antifreeze which might indicate a leaking heater core.
ATGO is not responsible for any damage done to your vehicle by following the above instructions.