Just returned from a great roadtrip in the STS. What a fabulous touring car.
My problem was apparently the passing I did as we were driving through rural Eastern Washington. Outside temps were about 41-45F.
I got a couple of "Coolant Hot" messages flick on and as I coasted down from 95MPH the message would go away and I watched the temp drop quickly from 240 to 195-200. It would only seem to get realy hot under two or three conseuctive full throttle blasts (imagine passing a car).
I checked the coolant and it is fine (just had it flushed and filled), and I assume the water pump is fine, otherwise I don't think it would have cooled down as fast as it did (in seconds) or at all.
My suspicion lies with the thermostat. The car is all original at 89K miles and wonder if anyone can think of anything else before I replace it. And also if you have any tips on replacing.
Thanks for reading, happy motoring.