1997 Ford F-100 Heater goes cold then overheats

ALASKAWAKE

MEMBER
1997 FORD F-100
V8
4WD
AUTOMATIC
121,000 MILES

The heater started going cold, then it overheats and blows coolant out pressurized tank. When heater starts working again, it cools fine and runs great. One mechanic replaced thermostat, the other replaced water pump. I picked it up and it did it again before I could get to work, mechanic picked me back up and changed out the thermostat, but it did it again on the way home. Ran fine after I pulled over and the heater started working again. He tested with the green to blue chemical for head gasket leak, but was negative. Any ideas? Another mechanic keeps saying "blown head gasket in early stages". Would you replace engine or do gasket job? Someone else said the catalytic converter could be bad. Help.

2 Replies

RASMATAZ

MECHANIC
75,992 POSTS

If the radiator is not clogged and fans are working and it passed the block test could be airlock in it try bleeding it and see what happens

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Saturday, June 12th, 2010 AT 3:52 AM

ALASKAWAKE

MEMBER
2 POSTS

The radiator is new. I'll check the fan. How do I bleed it, I tried once by parking on a hill tilting the cap to the highest point and letting it run with the radiator cap off. With all the changing of parts in the cooling system, would it lock up once and clear itself, or would it keep happening? The new thermostat has a hole in it the mechanic said to let bubbles through. I was going to drive it again today and see if it happened again.