I'm new to the forum. I just sold off my last VW bus and picked up a silver metallic '91 240 sedan for $650. I put new headlights and mounting brackets on it from a junkyard for $100 and it looks pretty good. All the power windows work, almost all the power locks work and my buddy with an R-12 tank charged the AC and that works too! Having driven air-cooled VW vans for several years, I'm not used to this level of refinement. Anyway, here's my problem:

The temperature gauge showed the car to occasionally come close to overheating. So, I flushed and filled while replacing the thermostat. No big deal, it probably needed done anyway. Then, the gauge still shows overheat situations. I happen upon your site and all it's lovely people, and disable the temperature compensator. I'm not the kind of guy who needs to compensate anyway. My question is this:

Knowing that my radiator is clean, my fan is turning, my coolant and thermostat are fresh and good and my water pump is neither leaking nor with bad bearings, what would be the next thing to check if my temperature goes sky-high again?

 

You need to check the temp with another thermometer to make sure that the car is in fact not overheating when the gauge is showing hot... Doesn't have to be anything super fancy, just a reliable gauge. It should read no more than 220-240F.

 

If it still overheats you need to check the cooling system pressure to test for an internal leak. Could be the head gasket.