Is the temp gauge electrical, or a Bourdon tube type? I'd suggest getting one of those infra-red temp checkers, like we use for tire temps on the race track, and doing a little testing at the thermostat housing or radiator top tank while the problem is happening. I'm betting you're having a gauge problem, not an actual overheating situation. The tire temp probes we use at the track register from below zero to 400 degrees F., and cost about 50 bucks. Well worth it, for any tool box. Just point and click, and the electronic readout comes up in about one second.
Jerry
