Boosted
Well-Known Member
My 2020 has a RT1252 as build. I purchased a RT1250 which is what I understand as the redesigned version. Would you still install this or just go for the RT1258?
Replaced factory RT1252 with RT1258 today
- Thread starter Hellwig
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
Mr Big
Full Access Members
The Motorcraft RT1250 Thermostat 190f/88, which is the same as the RT1258 specs. Check to make sure it will fit your 2020 Expedition Limited.
Are you sure they are the same specs? The RT1258 is 180 degree thermostat and I believe the RT1250 is a 195f/90.6.
Mr Big
Full Access Members
I'm not sure of anything. But if you go to an authorized Ford Parts site, all the specs are available for each thermostat. What I also find confusing is the RT-1258 specs show it is not for any Expedition. However, some thermostats are interchangeable. So, it doesn't mean it won't fit. You can plug your vehicle info here for fitment RT-1258.
Ford's site shows this, and no mention of any Expedition, which is causing more confusion:
From Ford Parts:
MOTORCRAFT RT1258 190 Degree Thermostat
Part Number: RT1258
Opening Temperature Rating (degrees F): 190 degrees F <---Notice it is not a 180-degree rated thermostat
Thermostat Flow Rate: Standard-flow
Vehicle Fitment:
Year Make Model Body & Trim Engine & Transmission
2025 Ford Explorer Platinum, ST 3.0L V6 - Gas
2025 Ford Police Interceptor Utility Base 3.0L V6 - Gas
2025 Lincoln Aviator Black Label, Livery, Premiere, Reserve 3.0L V6 - Gas
2024 Ford Explorer King Ranch, Platinum, ST 3.0L V6 - Gas
2024 Ford Mustang Dark Horse, Dark Horse Premium, GT, GT Premium 5.0L V8 - Gas
2024 Ford Police Interceptor Utility Base 3.0L V6 - Gas
2024 Lincoln Aviator Black Label, Livery, Premiere, Reserve 3.0L V6 - Gas
2023 Ford Explorer King Ranch, Platinum, ST 3.0L V6 - Gas
2023 Ford Mustang GT, GT Premium, Mach 1 5.0L V8 - Gas
2023 Ford Police Interceptor Utility Base 3.0L V6 - Gas
2023 Lincoln Aviator Base, Black Label, Black Label Grand Touring, Grand Touring, Livery, Reserve 3.0L V6 - Electric/Gas, 3.0L V6 - Gas
2022 Ford Explorer King Ranch, Platinum, ST 3.0L V6 - Gas
2022 Ford Mustang GT, GT Premium, Mach 1, Shelby GT500 5.0L V8 - Gas, 5.2L V8 - Gas
2022 Ford Police Interceptor Utility Base 3.0L V6 - Gas
2022 Lincoln Aviator Base, Black Label, Black Label Grand Touring, Grand Touring, Livery, Reserve 3.0L V6 - Electric/Gas, 3.0L V6 - Gas
2021 Ford Explorer King Ranch, Platinum, ST 3.0L V6 - Gas
2021 Ford Mustang GT, GT Premium, Mach 1, Shelby GT500 5.0L V8 - Gas, 5.2L V8 - Gas
2021 Ford Police Interceptor Utility Base 3.0L V6 - Gas
2021 Lincoln Aviator Base, Black Label, Black Label Grand Touring, Grand Touring, Reserve 3.0L V6 - Electric/Gas, 3.0L V6 - Gas
2020 Ford Explorer Platinum, ST 3.0L V6 - Gas
2020 Ford Mustang Bullitt, GT, GT Premium, Shelby GT350, Shelby GT350R, Shelby GT500 5.0L V8 - Gas, 5.2L V8 - Gas
2020 Ford Police Interceptor Utility Base 3.0L V6 - Gas
2020 Lincoln Aviator Base, Black Label, Black Label Grand Touring, Grand Touring, Reserve 3.0L V6 - Electric/Gas, 3.0L V6 - Gas
2020 Lincoln Continental Black Label, Coach Door Edition, Reserve 3.0L V6 - Gas
2019 Ford Mustang Bullitt, GT, GT Premium, Shelby GT350, Shelby GT350R 5.0L V8 - Gas, 5.2L V8 - Gas
2019 Lincoln Continental 80th Anniversary Coach Door Edition, Black Label, Reserve 3.0L V6 - Gas
2018 Ford Mustang GT, GT Premium, Shelby GT350, Shelby GT350R 5.0L V8 - Gas, 5.2L V8 - Gas
2018 Lincoln Continental Black Label, Reserve 3.0L V6 - Gas
2017 Ford Mustang GT, GT Premium, Shelby GT350, Shelby GT350R 5.0L V8 - Gas, 5.2L V8 - Gas
2017 Lincoln Continental Black Label, Reserve 3.0L V6 - Gas
2016 Ford Mustang GT, GT Premium, Shelby GT350, Shelby GT350R 5.0L V8 - Gas, 5.2L V8 - Gas
2015 Ford Mustang GT, GT 50 Years Limited Edition, GT Premium, Shelby GT350, Shelby GT350R 5.0L V8 - Gas, 5.2L V8 - Gas
2014 Ford Mustang GT 5.0L V8 - Gas
2013 Ford Mustang Boss 302, GT 5.0L V8 - Gas
2012 Ford Mustang Boss 302, GT 5.0L V8 - Gas
2011 Ford Mustang GT 5.0L V8 - Gas
I've been slammed and insulted for being persistent. However, the fact is, installing the wrong thermostat could cause serious damage to our vehicles. And like any forum, not all info is 100% correct.
Looking at that list, they are all smaller vehicles than Expedition/Navigator/F150 vehicles. It's possible that there are packaging differences that force a difference in design of the thermostat housing. It's also very possible that the cooling systems on these smaller vehicles are different from the larger vehicles thus warranting a different housing and a different set-point for the thermostat.
Also curious that the same thermostat is specified for 3.0 Ecoboost V6 vehicles and 5.0 and 5.2 Coyote V8 vehicles.
Mr Big
Full Access Members
I know, right? Very confusing.
I can confirm it fits and works...so far 
Edit: The link in post #44 shows the same thermostat I received and installed (rated at 82C/180F). Bottom line - If you want the lower 180 temp, the RT-1258 will work in a 2019 Expedition.
Edit: The link in post #44 shows the same thermostat I received and installed (rated at 82C/180F). Bottom line - If you want the lower 180 temp, the RT-1258 will work in a 2019 Expedition.
Last edited:
Hellwig
Full Access Members
Seal is RG640. I didn't re-use the old seal, although it's still relatively new.
Calidad
Full Access Members
This is 190F updated thermostat Ford put in my 2019 after having issues with the all metal thermostat sticking and causing temp issues.
The transmission temp can be monitored in the dash menus from zero F and up. Prior to the replacement at 75,000 miles transmission temperature was running warm all the time 210-220 unloaded mild temps low speed city driving. Fan was constantly running at 212 F. The thermostat failure was slow and progressively getting worse eventually triggering a coolant temp of 234 in cool temperatures at 70 mph on the highway with just me in the car.
After the 190F thermostat replacement
Highway transmission temperatures run 183-195 F. Stop and go in town 190-201 F. Towing my 8700lb boat through 40 minutes of heavy stop and go traffic 205-216 with it cooling down immediately to 200 while climbing a decent grade. Prior to the thermostat replacement I couldn’t get it to cool down beyond 210 from 227-230 even with 30 minutes of idling parked.
The F250 6.8L 6spd I recently used to drag my boat from sea level over a 7400ft pass. Ran 190-210F on the transmission temps over 190 mile haul.
I haven’t dragged the boat up that pass yet with the Expedition running the new thermostat. Last yr at 68,000 miles I tried and had cooling issues that seemed to get progressively worse and decided to get a friend to do the final haul of the boat. This was when I was starting to suspect a thermostat issue. Two months later no towing I saw the engine temp spike and knew the thermostat was failing.
One big difference between the Expedition and the F250. The F250 has a cooler on the transmission line with a fan. You can hear the fan kick on and see the temperature nose dive even under hard climbing conditions 2nd gear 3500rpm 40-45mph.
The Expedition only has the heat exchanger so as you load up the engine and generate more coolant heat you hit a point where the heat exchanger can’t efficiently cool the transmission. So the Expedition engine under high load generates heat which starts to degrade your ability to keep the transmission temps down.
The transmission temp can be monitored in the dash menus from zero F and up. Prior to the replacement at 75,000 miles transmission temperature was running warm all the time 210-220 unloaded mild temps low speed city driving. Fan was constantly running at 212 F. The thermostat failure was slow and progressively getting worse eventually triggering a coolant temp of 234 in cool temperatures at 70 mph on the highway with just me in the car.
After the 190F thermostat replacement
Highway transmission temperatures run 183-195 F. Stop and go in town 190-201 F. Towing my 8700lb boat through 40 minutes of heavy stop and go traffic 205-216 with it cooling down immediately to 200 while climbing a decent grade. Prior to the thermostat replacement I couldn’t get it to cool down beyond 210 from 227-230 even with 30 minutes of idling parked.
The F250 6.8L 6spd I recently used to drag my boat from sea level over a 7400ft pass. Ran 190-210F on the transmission temps over 190 mile haul.
I haven’t dragged the boat up that pass yet with the Expedition running the new thermostat. Last yr at 68,000 miles I tried and had cooling issues that seemed to get progressively worse and decided to get a friend to do the final haul of the boat. This was when I was starting to suspect a thermostat issue. Two months later no towing I saw the engine temp spike and knew the thermostat was failing.
One big difference between the Expedition and the F250. The F250 has a cooler on the transmission line with a fan. You can hear the fan kick on and see the temperature nose dive even under hard climbing conditions 2nd gear 3500rpm 40-45mph.
The Expedition only has the heat exchanger so as you load up the engine and generate more coolant heat you hit a point where the heat exchanger can’t efficiently cool the transmission. So the Expedition engine under high load generates heat which starts to degrade your ability to keep the transmission temps down.
Attachments
Let me add a data point to the thread. Count me as another happy convert to the 1258 thermostat. The 1258 was marked 82C and dropped my transmission temps 20* +/-.
2018 FX4/heavy duty tow. Transmission has always been run at 207 at light load and would run up to 215 in the heat of the summer or pulling a trailer. 150k miles. Swapped in the 1258 thermostat and left the truck wiht the dealer to have all the drive line fluids since it was time include transmission service. Just finished up about 10 hrs driving on a roadtrip. 1258 and fresh fluid. 184 trans temps under light load up to 191 for long highway pulls at 85 mph. Most of the trip I had to CC pinned at 80 mph. Moderate hills to flat and I got 19.5 MPG. Not bad for 150k miles, AT tires and a roof rack.
2018 FX4/heavy duty tow. Transmission has always been run at 207 at light load and would run up to 215 in the heat of the summer or pulling a trailer. 150k miles. Swapped in the 1258 thermostat and left the truck wiht the dealer to have all the drive line fluids since it was time include transmission service. Just finished up about 10 hrs driving on a roadtrip. 1258 and fresh fluid. 184 trans temps under light load up to 191 for long highway pulls at 85 mph. Most of the trip I had to CC pinned at 80 mph. Moderate hills to flat and I got 19.5 MPG. Not bad for 150k miles, AT tires and a roof rack.
Similar threads
