I have an 87 trans am 350 tpi. Its been overheathing a lot specially in hot weather. The overflow tank gets full and starts to boil. I replaced the water pump for a new1. The thermostat is new. I flush the radiator. The air dam is in good shape. I notice that the temperature gets higher when the car is not moving. I don't know what else to do.

Turn your car on in your drive way and open the hood. Then turn on your Air Conditioner. Do your fans come on?

If they do, then the fans work as does the relay that controls them, thus all of your fuses are good by defaut.. Turn off the AC and watch your Temp Gauge. When the temp gets around 220 degrees or so, your fans should turn on. Do they?

If they do not, there is your problem. Most likely is the fan sensor located on your passenger side head or the wiring going to it.

If your fans work, another thing you can do is take your radiator cap down to your local sears auto center (only because I know for a fact they do this--not sure who else does), and ask them to do a pressure check on it. Should be around 16psi or so. If it's not, this could be part of your problem as it's not holding the proper pressure in your radiator.

Hope this helps.

i agree that sounds like some grimlins in your fans or in your wiring.

Check the front of the radiator (hard to do wihout removing parts), I have found complete blockage of the fins behind the A/C condensor which reduces the radiator cooling by 20% or more. This is a out of sight condition which requires effort to check..