1999 Ford F-150 Over heating but no steaming.

PHILDMAC

MEMBER
1999 FORD F-150
4.6L
V8
4WD
AUTOMATIC
239,000 MILES

I had trouble last year no heat and the heat gauge would go to the top than down to mid way. Put in a new thermostat no help, ford dealer put a new water pump, worked good all summer and fall. In dec. It started acting up again, some times heat some times not. Some times there is heat and it will start to blow cold air, if I turn the blower switch off than back on it will blow hot for a while than maybe cold again some times not. I have been told head gasket or cracked head I just don't know what to think.

6 Replies

JACOBANDNICKOLAS

MECHANIC
109,896 POSTS

Is the coolant full? Are you using coolant?

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Tuesday, January 13th, 2015 AT 6:45 PM

PHILDMAC

MEMBER
4 POSTS

Yes I have to add 1/2 gal per week some times less.

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Wednesday, January 14th, 2015 AT 3:39 PM

JACOBANDNICKOLAS

MECHANIC
109,896 POSTS

Okay, we need to determine where the coolant is going. Are there any leaks that you see? Have you checked the engine oil to make sure it isn't mixing with coolant? By any chance, is there excessive white smoke from the exhaust?

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Wednesday, January 14th, 2015 AT 6:08 PM

PHILDMAC

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4 POSTS

No smoke no fluid in oil and no leaks

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Thursday, January 15th, 2015 AT 3:04 PM

JACOBANDNICKOLAS

MECHANIC
109,896 POSTS

Okay, then I doubt there is a problem with the heads or gaskets. Since you can turn the heat off for a period and then get heat again temporarily, it sounds like the heater core may be partially blocked. Try flushing the heater core and see if that takes care of the issue.