Thermostat OEM Volkswagen or Motorcraft

Your thermostat is probably stuck open. Replace it with an OEM Motorcraft version, not aftermarket.

I had a bad thermostat and it's only indication was the temp rising when going up hills under sustained load.

I had this year ago, thermostat was stuck closed, so coolant couldnt go to big circle and into cooler, it went up after 10 minutes of highway driving up to 115° (obd temps) on dash it wasnt that much

I used the genuine part as there is no desire to redo it again too soon.

It has been two weeks since the repair without issues, so I am going to call this one solved. If I was paying for this out of pocket in the future, I would only replace the thermostat and not the pump as that is what was closing and causing the issue.

The Motorcraft thermostat sounds promising though, never have an issue with genuine ford parts.

I replaced the thermostat from a non-OEM to Motorcraft about a month ago, and the only difference has been the speed at which the dial moves from higher temps to its normal positon.

Sounds like your water pump is working, but maybe your thermostat is stuck closed? Have you tested the thermostat?

Original was stuck open, replaced with new VW which now appears to be stuck closed. ????. Fortunately I have recently acquired a new OE thermostat on clearance for jollies.

I bought a Motorcraft thermostat from the Ford dealer for my Crown Vic and it ran about 20 degrees cold.