Ok, Ive been trying to diagnose the problem myself for 2 nights now to no avail. Dad has an 00 F150 with the 6 along with a manual transmission. 2x4. For some reason, especially when hes going down the highway any distance the temperature gauge shoots up to high, the coolant light comes on, low oil pressure light comes on as well. We checked the fluids, it doesnt really seem to be missing anything. Its a little low on oil, but I know it is burning some out the exhaust. I flushed the coolant with this prestone super flush stuff, new coolant, had new plugs about 50 k ago, new filters, basically a tuneup. Put a new thermostat in it. Truck is sitting right at 200 k. Any body have any ideas as to what may be causing this? Thanks in advance!

 

First things I think of:

Radiator needs cleaning out or replacing. It seems the DIY flush won't solve the problem. Professional clean out or replacement is required.
Air bubble trapped in the coolant system. (left over from the flush/fill)

Bad thermostat (did the problem start after installing new thermostat?)

Some sort of electrical problem causing false indications.

I'm probably missing the real cause.

Maybe somebody else will chime in.

 

I had a F150 302 that would run fine all day around town and never overheat. As soon as I would hit the highway go about 60, the temps would rise. My lower radiator hose was being sucked closed because the spring inside the hose had failed. If the bottom hose is soft it might be part of your problem
HTH
regards
rikard

 

Have the coolant tested for exhaust gasses.

Methinks you might have a blown head gasket.

Steve