1994 f150 xlt 5.8l 2wd
temp is in normal range most of the time. when at highway speeds/2500 to 3000 rpm temp gauge is almost to the red line. Moves around a little at the last white line and back to the L in "Normal" and sometimes back close to the red line. Not loosing fluid. Have changed the thermostat twice with last one from Ford. I can see the thermostat open and temp drop on the gauge when running around in town. Would not think fan clutch is the issue because its at speed when I have the issue. What should I check for? Any thoughts?

 

Did you ever figure this out? I'm having this exact problem and have replaced the whole cooling system but the heater core. 92 E250 5.8

 

no.
oddly enough my temp problems only occur in the winter and spring, and not all the time. runs on low end of normal now that its 100 degrees outside.

 

FYI this was repaired. Random overheating was from timing cover leak. Air getting sucked in or trapped was causing the problem. Runs on the low end of "Normal" now. Replaced water pump and timing chain while it was opened up.

 

Thanks for updating this! Glad to know you found and fixed the problem.