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Discussion Starter · #1 ·
My 2020 Supercrew is back in the shop again. Literally a few days after getting it back from them replacing the wiring harness with the knock sensors and coolant sensor I noticed the engine was running cold and taking forever to warm up. Sometimes you will be sitting at a traffic light and the temperature gauge will just start dropping back down to the cold. And then to make things even more complex, there are days it is fine and runs between 190-200 degrees. Last Friday I drove the whole way home with no heat. The engine just would not get warm. Then the next day I ran some errands and it ran fine with temps between 190-200 degrees all day. Any help here would be appreciated because the dealership is perplexed why it's doing this. I have 3 hours of video on my phone of me driving with the temperature gauge barely moving off the cold. The shutters are working as they are supposed too. I even went as far as using the infrared temperature gun to check engine temperatures on days the temperature gauge was reading on the cold side to see if the engine was actually running cold and it was. After a half hour of driving I got a reading of 130 degrees off the front of the cylinder heads. The issue is, without the truck kicking a fault code they really can't do much. Also for those who don't know, the cooling system runs on a series of valves that open and close to control engine temperature. It's a very complex and overengineered system and the service manager said it could take days to figure out why somedays the truck runs cold and other days it runs hot. Anybody who has experienced this before or who might be able to help us out please feel free to comment.
 

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2021 Powerboost Platinum FX4 Kodiak Brown
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Well, that's a unique quandary around here.
I don't think I ever remember anything like it.

When you say that it is running 190-200 when things are normal, where are those numerical values coming from? (Forscan enabled dash, or ODB connected pid)

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Discussion Starter · #4 ·
Well, that's a unique quandary around here.
I don't think I ever remember anything like it.

When you say that it is running 190-200 when things are normal, where are those numerical values coming from? (Forscan enabled dash, or ODB connected pid)

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Those temperature readings are coming right from the temperature sensor via the OBDII port. I have forscan, and a couple apps and they all are on the same page. I have also done some data logging. The dealership did the same thing. Hooked their laptop up to the truck and drove it.
 

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2021 Powerboost Platinum FX4 Kodiak Brown
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OK. I had to ask. No offense but it's truly an odd consideration that an Ecoboost F150 is running too cool. And so the first natural opinion is "that can't be", therefore the notoriously misleading dash gauge must be the culprit.

But if the pcm is stating those cold temperatures, that's a different story. Amazing. I didn't even think the cooling system on these trucks could shed enough heat to bar the truck from reaching higher Temps than 130F

Bottle it and sell it to the 3.5 summer towing crowd!

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Discussion Starter · #7 ·
OK. I had to ask. No offense but it's truly an odd consideration that an Ecoboost F150 is running too cool. And so the first natural opinion is "that can't be", therefore the notoriously misleading dash gauge must be the culprit.

But if the pcm is stating those cold temperatures, that's a different story. Amazing. I didn't even think the cooling system on these trucks could shed enough heat to bar the truck from reaching higher Temps than 130F

Bottle it and sell it to the 3.5 summer towing crowd!

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Yah it is a weird thing and like I said, the service manager has never seen anything like it. We sat there and I showed him some videos of me driving around and the temperature gauge all of a sudden just goes back to the cold side and he was perplexed. When I get home from work and can grab the top radiator hose with my hand and hold it there for a minute and not get burned, then you know something is wrong...
 

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Has the truck always ran cool since you bought it? What were the issues you were having that caused it to need the initial repairs you mentioned?


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Sounds like something may be causing your T-stat to stick. Has that been replaced? I don't know how many T-stats I have had that either have stuck open (most common) or stuck close (happened only a couple of times). And just because it's new, doesn't mean it can't fail.

And don't settle for the "they tested it". Get a new one installed. EVEN if they say they installed a new one.
 
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Sounds like something may be causing your T-stat to stick. Has that been replaced? I don't know how many T-stats I have had that either have stuck open (most common) or stuck close (happened only a couple of times). And just because it's new, doesn't mean it can't fail.

And don't settle for the "they tested it". Get a new one installed. EVEN if they say they installed a new one.
True story

Bought my wife's explorer, used. It would never heat up, it was around 10f at the time. Pull the t-stat housing and found a chunk of gasket lodged between the base and spring, forcing it to always be open.

Anything is possible.
 

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t-stat for sure.

And I dont know why the truck would ever throw a code for a faulty t-stat so its kind of a stupid situation.
 
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