I recently replaced both serpentine belts on my 05 M6. Prior to replacing is had a hell of a squeel. So two days later I noticed the temp on my guage climb a couple notches on the guage and instantly drop back down to normal operating temp (I'm assuming the t-stat was stuck or the fan kicked in). This happened again yesterday, after following a hard freeze over night (15 Deg). The vehicle had been running for a good 30 min on the freeway prior to the temp starting to climb. No coolant leaking. No more squeeling since I changed the belts. I'm thinking T-Stat is sticking, however that T-Stat was replaced last year so its not very old. Guess it could be defective....thoughts??