I am asking this for my step dad he has a 1989 Firebird with a 2.8 v6 and the car will overheat sporadically. somedays it will over heat before he can get down the road a mile and otherdays it will go hours with out overheating. I have racked my brain for the last few weeks trying to figure this problem out and correct it. I have check everything in the cooling system and it all seems to work fine but nothing has solved the problem.

 

Bump

 

Sounds like the thermostat may be sticking. You may want to replace it with a 180 high flow if it has been in there a long time. Summit has one I use, Part # EMP-301. You can also replace the fan switch for one that comes on at 185-200 instead of the factory 225 or so.