I have a 1991 Toyota pickup, 4 cylinder that overheats going up steep grades. I've replaced the fan clutch, water pump and flushed the system. No rust. It runs well. So I don't know what else could cause it to over-heat. The water circulates through the radiator at the top pretty well and there is no foaming like it would for a warped head gasket. What else is there?

 

Blocked Radiator ??

Auto or Manual ??

Auto transmission dumping more heat into the cooling system then it can handle

 

Make sure the ignition timing is at spec.

Engines out of time often throw extra heat into the cooling system.

 

manual transmission. suspecting a blown head gasket. Radiator seems to have good flow. it's 10 years old though.