I have an 86 T/A with the single fan set up. the car seems to run cool enough on the city driving but when you get it on the highway the temp goes up and there is a notable pinging from the engine like spark nock. I also noticed that even in the city when the fan comes on at about 190 it stays on and dont go out till you turn of the car? I already put in a new waterpump, thermastat, radiator cap. Heat is good. Any ideas?

 

make sure you have on your air dam underneath the car it helps to push air up to the radiator on the highway, ive heard of this causing overheating in my buds trans am.

 

You should also have a bunch of plastic pieces on the front side of the radiator that shroud the sides of it, forming a ram effect for the air to pass through. If you don't have those installed, that will also cause the car to run hotter on the highway. The airdam is the big thing though. If you don't have that you will run alot hotter at speed. My old 85 didn't have one when I got it, so we made one for it and promptly dropped at least 40 deg on the hwy.

Good luck

 

Also, check to see if the radiator is clogged. Had this problem with my Ranger. Ran hot on the freeway, and cooled off in city driving. An easy way to check this is to feel along the face of the radiator after the car has been driven. Mine was smoking hot along the top few rows, and the rest was cool to the touch. After removing the coolant, the problem became very obvious, as the core was mostly plugged by years of gunk.