New thermostat works!

[HiTechRedneck]

New ride new part. 2020 Navi BL

2017-2022 Ford Engine Coolant Thermostat HL3Z-8575-B | TascaParts.com

2017-2022 Ford part # HL3Z-8575-B - Engine Coolant Thermostat

www.tascaparts.com

This T-stat HL3Z 8575 B comes in at 182 degrees f. Which means it starts opening at 182 and is likely fully open at 197 to 202. Again with engine coolant temps in the range just over 200 degrees on a warmed up engine. (at the thermostat of course)

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So let me see.... Now you're telling us that the correct thermostat according to Tasca opens at 189?

 

[Action]

Based on service replacement parts at an authorized Ford dealership
For 2020 Navigator 182 degrees f
For 2020 Aviator 189 degrees f

The temperature of the thermostat is when it starts to open.
The fully opened point of a thermostat is about 15/20 degrees higher.
Which creates an operating temperature well over 200 degrees f.

The thermostat does not control how hot the system operates. It controls how fast and how high the cooling system warms up. After the thermostat has reached it's fully opened point, it is no longer doing much as coolant is free flowing into the radiator.
What controls the cooling of the hot coolant is air blowing through the radiator and the water pump moving the coolant.
And what I have said and will continue to say is the cooling systems are designed to operate over 200 degrees f. Normal would be over 205 degrees and higher. Temps of 215 to 220 are very common.

In post #1, you posted, "Temp never got over 200, stayed at 190 most of the time." on a 300+ mile trip
Coolant under 200 degrees f is a problem on a warmed up engine. It is too cold. Especially on an Ecoboost engine that is direct injected and boosted. The crankcase has more blow-by than a naturally aspirated engine
I have not seen and no one has posted about an old or new (rated) thermostat. Post #11. Still waiting for that answer.

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[NavigatorPro]

The specific problem with the old thermostat was it seemed to get stuck closed. If you look at old versus new...the new one seems more robust and of a different design.

 

[Action]

^^ +1
Thanks for the clarification.

And there is no difference in the temperature rating. Both are 182.

Since this thread does not have the thermostat part numbers here it is. These are Motorcraft numbers not full Ford part numbers.
RT 1238 - previous
RT 1252 - new

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[NavigatorPro]

The additional thing to know about thermostats are there are no forever thermostats and they usually fail slowly. So its good to keep an eye out on things and if the temperature gets loose probably the stat is worn out. Someone said 7 years life on a stat but I have had quite a few fail open and close on different vehicles way before 7 years. Basically its a wear away item and not a forever item. If you feel like something wrong with the cooling system dont be afraid to change the stat first.

 

[Action]

My 2006 still has the original stat.

Since my ownership (bought used about 90,000 miles ago) I have replaced the coolant 3 times. (drain and refill) I did it when I bought it and 2 other times most recently this spring.

Mind you I have a 5.4l V8. Different kind of engine.

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[NavigatorPro]

I had a 1991 Ford.Mustang 5.0 when.one day Im guessing in 1994 there was no heat meaning stuck open. It comes down to a lot of factors.

When it comes to a 440 horsepower bi-turbo beast used in severe or extreme service settings you have to watch everything closely. Looking..listening...questioning...