jpfarfalle

So I have a 2020 F150 with a 2.7. I got it CPO (or whatever that means because it keeps breaking lol) in September of last year.

So I’m having an issue with my cooling system. I drive 50 miles each way to work daily so I’ll remote start my truck and I’lol start driving. It’s about 60 degrees here in NJ on my way to work. So I’ll get on the highway going about 70 MPH and it will warm up and get close to what shows OT on the dash. Then it will just slowly drop. With my Bluetooth OBD scanner plugged in I’ll see the temps get to about 175 and then slowly plummet.

If I accelerate hard sometimes the temperatures wil go right back to 205 which is where it will sit when I don’t have a problem. Other times it will just drop all the way and the truck goes into limp mode and throws a DTC P1299 which is cylinder head over temp. If I clear it the temp goes right back to 205. Truck comes out of limp mode and is fine until it drops again.

Let me mention if I let the truck warm up without driving for about a half hour I usually don’t have this issue. If I start the truck and drive immediately without warming up It typically won’t ever get to OT or it will go all over the place.

let me mention that once when the truck wouldn’t “warm up” i opened the coolant tank and put my no spill funnel in to see if I had air and there was a huge surge of coolant after idling the truck for a few minutes and around 3200 rpm.

im thinking a **** thermostat at this point. The thing that confuses me is why if I’m at the supposed 205 and it starts to cool down how could that be the thermostat. Unless it’s closing and throwing a check engine light because it’s actually over heating. I’ve never seen a temp over 215. The truck is still under warranty but my dealership is useless. They refuse to fix anything unless it comes in visibly broken and they have “looked” at this before and said it was normal.

any thoughts would be greatly appreciated. Thanks in advanced.

4XFarce

Sounds like an air pocket in the cooling system. My Ranger did something similar after changing the temperature sensor and it was a pain to purge all the air out of it. The recommended procedure for them is to put it on ramps or on an incline, turn the heater on full blast and let it run for a half hour with the radiator cap off. Each time the thermostat opened it would purge a bunch of air and I would then continue topping off the radiator as the coolant level dropped. Took about 4 cycles of the thermostat opening to get all the air out. It’s the only vehicle I’ve ever owned that was a pain to purge air out of the cooling system. Maybe it’s a Ford thing. Could be your issue or could be a sticking thermostat.

Blue2016XL

Other possibility is to make sure the correct thermostat was used. I believe, but could be wrong, Ford uses a different style of thermostat than other manufacturers. At least on the F150. Somewhere on here there is a thread that explains the difference.

jpfarfalle

this makes sense and it’s what I’m thinking, but why would air be introduced into the system all of a sudden? I guess I don’t know what the previous owner has done. Today before leaving work I started the truck let it idle for about 15 minutes with the air conditioning on and it was out operating temperature and it’s been good on the highway so far. Guessing thermostat and or air on the system. That will be my weekend project.