I have a weird overheating problem, I was gonna see if anyone could diagnose it. I have a 91 LS and it only overheats when I go over this mountain on my way to work. It's the strangest thing. I can be driving 40mph and it can be 63 degree's outside and it'll start overheating once it I get to the top of the mountain(Mulholland). To make it stop, I just turn the heater on full blast and that seems to work. But still, it's a nuisance. Any help is appreciated.

 

could need a new thermostat, mine was doing that too except it would only cool down when i was stopped, and i changed the thermostat and it has been fine for the last 2 weeks atleast.

 

Im no expert but i would guess a combination of the extra work to get up the mountain and the higher altitude (less dense air carrying less heat away from radiator) could cause the overheating. If this is the only time it overheats, then i cant really imagine something being defective, its probably just the conditions that cause it.