1990 Ford Bronco Teperature runs from Lower to upper end of

1990 FORD BRONCO
119,000 MILES • V8 • 4WD • AUTOMATIC
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PAUL ANDRESEN
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I ran hot and blew my head gasket. I had new heads put on as well as new radiator and hoses. I drove Truck a couple of days ago and was running hot . The red light for check engine came on. When I got the Truck home I decided to swap out the thremostat. It had never been replaced by the mechanic when I had all of the work done. Now with a new thermo, ( installed facing the right way) max temp 195 deg. the gauge goes down to the N and runs up to the L back and forth like this. I also took the Truck out of overdrive RPM at 2500 and it jumped above the L. I am affraid to overheat this Truck again, the last time ran me over 3K. Any ideas why it is jumping around so much.
Jul 18, 2008 at 12:09 PM
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DOCFIXIT
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If the engine is not getting hot my guess is the temp sender was fried on the overheat. Have you put a new one in since overheat?
Jul 18, 2008 at 12:24 PM
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RASMATAZ
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Have it block and pressure tested-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: Thermostat,Pressure test the Rad. cap,Clogged radiator,Fan clutch,Radiator electrical fan,collaspe hoses,water pump.
Jul 18, 2008 at 12:25 PM
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