I already had a new thermostat so I went ahead and swapped it. I tested the old one, and the new one, in 190 degree water and they both opened up. Darn.
Test drove it. The wrench is still on but I expected that. After a few miles the Engine Coolant Over Temperature came on again. I set the dash to show coolant temp and it showed 81 C (177.8 F). The coolant level is topped off and reads fine.
Is there a way to test the water pump without taking it out? Any other suggestions?
The dealer is backed up for a couple of weeks!
Thanks.