I have a 86 gxl i just swaped a motor into, the motor runs really strong. The one thing it does do is very weird how it overheats. I can drive it around town for hours in town and the temp guage would be normal temp. I would take it on the high ways the heat would raise from 1/4 of the way to half way, when i would slow down from doing about 80 (consistant speed) then the guage would starn moving not creeping to hot. I never let it get really hot about 3/4 of the way up. Some times it would give me symptoms of a blown motor with the blow back out of the resivor bottle. It has a new thermostat, cooling systems been flushed, 2 e-fans 1pushes and 1 pulls they are both are wired on a relay and turns on as the car does, the heater core is good and radiator doesnt leak, there is new coolant in the whole system.
If anyone can help at all plz toss some ideas
-Tea-