It might be the computer-its job is to energize the fan relay relay when it senses the correct temperature from the coolant temperature sensor or a coolant temperature gauge sending unit.
Doing a block and pressure tests will help find what's causing it to overheat.
Do the block first to pinpoint a combustion leaking into the cooling system or a gas analyzer to sniff for hydrocarbons at the radiator fill neck.
Pressure test: do not do a pressure test if there's leakage at the headgasket this might cause coolant into the cylinders and lock it up or bend a connecting rod if cranked thereafter. The headgasket should be repaired before doing the pressure test.
If the block and pressure test passes check the following: ,Pressure test the Rad. cap,Clogged radiator,air lock in the cooling system ,Fan clutch,Radiator electrical fan,collaspe hoses,water pump.
Sep 28, 2008 at 6:52 PM
