The Motorcraft F6TZ-8575-EA is the factory thermostat for a 1996–2003 7.3 Powerstroke. Motorcraft lists it as RT-1201. It replaces F6TZ-8575-BA, F9TZ-8575-AA, RT-1125, and RT-1197.

It is the long-stem thermostat for the stock water pump and the stock housing. A thermostat that sticks open runs cold and the heater stays weak. A thermostat that sticks shut overheats on a grade. The DieselSite pump kits use the International short-stem 205-degree thermostat. This one does not go in that pump. The housing ring is Driven Diesel DD-73L-TSHR. The billet housing is Beans 220050.

It fits 1996–2003 F-250 through F-550, E-Series, and 2000–2003 Excursion trucks with the 7.3.

Fitment

• 1996–2003 Ford 7.3L Powerstroke
• Super Duty, E-Series, and Excursion
• Genuine Motorcraft F6TZ-8575-EA
• Stock water pump
• Housing not included

Replace the O-ring or the seal with it. Bleed the system until the thermostat opens. A low degas bottle is air in the heads.