As a form of habit, I just change my thermostat when I do a coolant change every 2-3 years. When there is no coolant in it, all there is to do is unbolt the housing, stick the new one in, put in a new seal and put the housing back on.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record