🔧 Improved Motorcraft RT1139 Thermostat for Enhanced Engine Performance Review

Ordered for 1991 Explorer. Does not fit The front of the thermostat has a protrusion that does not fit the opening in the case. A return is unfortunately not possible, as it is stated on the packaging that it is non-returnable if opened.

This is a 192F thermostat. It's a real Motorcraft and that's all I want to use for it. I went back and bought an extra one to have on hand. I boiled it in water to compare to my old thermostat and it opens a lot more so it's no wonder why my engine was running hot.

As others have said, install Motorcraft parts in your Ford and you will have fewer problems. In my case I had a subtle cooling problem about 5 years/15k ago and bought a new thermostat from a local shop. It wasn't Motorcraft and guess what I had to replace again this week?

Yes, it costs 3x more than other aftermarket thermostats. But you get what you paid for. This thermostat serves its purpose while keeping my EEC 4 happy. (Always use a 192 degree thermostat for EEC 4 units or your car/truck will run rich and possibly fail the emissions test and recycle the fuel. You will also get more heat from the heater)