Not sure if it's overheating.

[gabe4]

I've got a 98 with A/C. I tow a pop-up but this happend before as well. I'll be running along at like 220 then bam the temp gage maxes out the check gage light comes on. I pull over to check and nothing seems to be boiling over or anything indicating that it's hot the overflow looks like it's would normally. If I let it sit the temp gage gose back down which makes me think it's working ok. I suspect maybe the thermostat is not working correctly. Any suggestions.

[heeperman]

i would be looking at your temperature sending unit, begin with just cleaning the contact point, and see if that helps, if your gauge spikes you should definately be able to see signs of overheating (ie coolant overflow bottle boiling etc...)

[gabe4]

Is that what controls the thermostat, as far as opening and closeing it. This dose this only in situations that might make the motor run hot anyway, normally when going up a large hill with the AC on or if I'm towing.

[heeperman]

its what sends the signal to your gauge, your thermostat is mechanical and it controls itself, if your t-stat wasn't working you would either be over cooling or overheating, as it usually fails by remaining open or in the closed position. With your engine cold, remove your rad cap, start it up and watch the coolant in the rad, when the engine warms up and the t-stat opens you should begin to see the coolant flowing in the rad. Seeing as your issue is intermittent go with the sending unit first, seeing as its nice and easy to change and cost about $9

[gabe4]

I'll try that plus get it flushed out maybe that will help.

[87manche]

might want to look at the radiator cap too. As the motor heats up it may max out the pressure in the system, if the cap isn't holding you'll get a sudden spike/boilover.
Have it pressure tested or just get a new one. Cheap insurance.