Mechanics

OVERHEATING 97

1979 Ford F-150 • V8 4WD Automatic • 135,000 miles

I have 97 f-150 4x4 extra cab with the 4.6 ltr v-8. A couple of weeks ago I warmed it up for work and acouple miles down the road my heater went cold and I noticed the temp gage dropping. It dropped to a little above cold and stopped and a minute later shot to the top. I turned the heater off and a minute later it dropped back down to normal and I was able to turn the heater back on and it held normal all the way to work. It did the same on the way home. Thinking it was the thermostat I went to napa and bought a new one and replaced it. I had to ad about a half galon of coolant. All was well for a few days when on my way home from work it did the same thing. I found where a little coolant escaped out the pressure cap so I went and replaced it, I really didnt have to add much for coolant this time. Again all was ok for a few days and it started again. There is no white steam from the exhaust, the fan clutch appears to be doing ok, theres no water in the oil, it has a new thermostat and coolant cap, things appear to be clean, and there appears to be no leak. I would be very gratefull if you could help me out with this mystery. Thanks, wa
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Username97
February 5, 2011.




Pressure test coolant system
white steam from the exhaust usually is an indication of a head gasket failure

BMRFIXIT
Feb 5, 2011.


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