I have a 97 f150 with a coolant problem. In the morning when truck is cold the temp gauge comes up to temperature then I loose the heat and the temp gauge goes to cold. Temp gauge starts rising past normal going to hot then drops to normal and heat returns. The system has been flushed 4 times, heater core has been changed, and thermostat has been changed 3 times. The cylinder sensor has been changed along with the radiator and cap. What do I do? Bob
Water pump and/or drive belt comes to mind based on the other things you have tried.
Chris
Or air trapped in the system.
Of course I'm still trying to figure out how heat gets "loose" ;)
check the water pump and belt. check for kinked hoses
or collapsed heater hoses, or blockage of some sort in any hoses.
One other possibility is a blocked heater core.
Are you losing coolant?
-jim
By loose (lose) the heat do you mean that no heat comes from the heater?
Yes I lose heat not heat at all. Temp Gauge goes to cold then past normal with still no heat then drops back to normal heat returns.
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