Overheating 2.5NA

[RoverDover]

My deefer got a bit hot the other day. I decided to replace the thermostat today, upon refilling the coolant through the expansion tank I noticed the cap did not sit well. upon further examination it appears the lobes that hold the cap on have been bent out of shape and hammered back into shape. I never noticed this before because I never has an overheating problem before...could this be the culprit?

[RoverDover]

I replaced my expansion tank and cap, got in the truck and went for a drive. The temperature held steady at the mid range until I hit a pothole. suddenly the gage went through the roof! I turned the head lights off and the gage settled back down in seconds, I turned the headlight back on and the gage went through the roof again. Any Ideas which wires I should be tracing to find the problem?

[SafeAirOne]

Your instrument panel ground is bad. The instrument panel lights are grounding (sending their voltage) through the fuel and temp gauge circuits instead of the normal way.

Make sure those thumb nuts that hold the instruments onto the instrument panel are tight--THat's what usually cures it for me.

[RoverDover]

that makes a lot of sense (not that I would have thought of it on my own though) Thanks, I will check it out tomorrow night.

[SafeAirOne]

This has happened to me on more than one occasion. There's nothing quite as...invigorating...as driving along at night and seeing your temp gauge pegged beyond the "H"!