I appreciate the WAG. I'll start tracking trans temp as well. It didn't seem to move, but I wasn't thinking the trans played a part. Speed seems to matter. I can only really do this on the highway - I don't see this happen in town. Tho, when in town, I can make it get up to 226/228, but the digital temp doesn't show until 230 - and I can only do that when I soak it on the highway.

I have been watching the front grill as well to make sure they are not obstructed, etc...

One of the advisers at the dealer suggested getting a IR thermometer and measuring in various places to see if there is a drastic change in temp from say the radiator inlet to the thermostat, etc... I may try to pick up a harbor freight special and see what that yields.

I'll post a screenshot of the forscan scope output as well -- maybe that will trigger something.

 

Read that many trucks with the orange coolant were having clogging issues, especially the heater core, so I'd change the coolant now. If I keep the truck, will do it at 50K miles out of precaution. Also to only do a drain and refill with a similar DexCool approved orange coolant. If you wait longer, might have to do a full flush, which would be a lot more expensive. Having said that, if you already have blockage, you might not only need a flush, but a special product to remove blockages. If that's the case, make a powertrain claim. I want to do a coolant change to precisely avoid having to deal with that. Good luck.

 

The VCT repair required a coolant drain/fill since the front half of the engine had to come off. I'm convinced something during the repair caused this issue. Prior to the repair, I had no issues merging on the highway, or towing the trailer, driving the mountains, or any sort of cooling issue. My truck is mostly a pavement princess, so it wasn't immediately obvious something was wrong after the repair. I'm 6 city miles from work, so it doesn't really get exercised much. But, a month-ish after the repair, my daughter told me she saw the temp rise on her T-giving trip w/ her horse. The idiot gauge didn't really move from center, so she didn't think anything of it until after I said something happened on my trip.

The other thing that was weird - is that I lost cabin heat in the mountains. It doesn't really get cold enough in Dallas generally to notice that particular side effect. I'm not sure if that was related to the temp spikes, or simply coincidence that it would get really cold in the cab.

 

I found this TSB regarding the coolant issue you were referring to. While it will be impossible to test in 4F temps here in Dallas, I am still going to run thru the motions and see what temps I see. I'll have to dig for the heater core inlet/outlet hoses. I'm assuming those will be obvious under the hood? Probably buried behind/under the engine cover? I hope there is a better solution -- replacing the heater core sucks (well, for the tech anyway) and likely for the dash too.

TECHNICAL SERVICE BULLETIN 3.3L/3.5L Duratec/3.5L EcoBoost/5.0L - Without Block Heater - Lack Of Heat When Operating In Temperatures Below -20°C (4°F) 18-2244 20 August 2018
https://static.nhtsa.gov/odi/tsbs/20...44911-9999.pdf

 

I created an account to post about this issue. I have a 2017 3.5 Ecoboost. At 58000 miles I took my truck in to fix the VCT phaser rattle. Immediately after I got the truck back I noticed a plastic burning smell whenever I would come to a stop after traveling at higher speeds on the interstate. Strong enough that I could smell it inside the truck and very strong standing outside the truck. At one point I noticed smoke coming out from the right side of the hood as I was sitting in the truck. I’ve taken it in twice and will be going back tomorrow as they have been unable to fix the issue. I will ask tomorrow what they “fixed” each time trying to address it. Today for the first time I noticed the engine coolant temperature flash above the meter on the dash. It was only there for a few seconds but I want to say it was around 220 degrees.

I’m sorry that you are having the same trouble but I have to say it’s a little comforting to know I’m not alone, haha. This has been really frustrating. Please keep me updated if you are able to find an answer to what sounds like is both of our problems and I’ll do the same. Like you, I am certain that this issue is a result of the VCT rattle repair.

 

You probably saw 230. Digital temp doesn't come in until 230, and goes away at 225. I've got 234 holding cruise at 55 up a ridiculously small hill. I tried to verify the heater core temps in the tsb but it doesn't seem like my problem is in the heater core. I would like to hear what you have tried tho. I think I'm going to another dealer - my long time repair center just doesn't seem to give a fsck.

Watching my coolant temps on forscan generally stays around 219-225 in town at 45mph.

My sense of smell is terrible - I might have smelled something on the way home but I think it's just hypersensitivity. I am certain I lost cabin heat coming through the mountains over Christmas. Outside temp was in the high single digits. Cabin temp was fine, then it would get cold. I wasn't able to think clearly enough at the time to try and correlate cabin heat with digital temp showing up.

 

try unplugging the connector at the top of the radiator that controls the active grill shutters. Confirm they are completely open when doing this and they will stay open while you drive. Simple test to rule these out as the issue. Someone else had these fail closed and had similar issues to yours. No way should you be seeing those temps without a trailer attached.

 

got the truck back yesterday and so far so good.

"Added oil dye test, oil coming from high pressure pump and number 1 coil tower seal - removed intake and pass idea valve cover - replace coil seal and fuel pump"

 

Took mine in again - they pulled a P05B0/P05B6 code which is a grill issue - however, I think this is a red herring as the grills seemed to be working fine. In the spirit of not messing with the machine, I let them go thru the motion of replacing the upper grill. I did a quick test drive and was able to reproduce the high temp. I returned to the service drive with the fans howling. However, this time, I was able to get a tech to do a ride along. (Shout out David!) I again reproduced the problem - even better than before topping out at 236 after going on the overpass. He definitely agreed something was amiss.

My only easy hope now is the TSB. One part of me hopes to find a root cause, the other doesn't really want my dash to have to be torn apart. It really feels like obstructed flow is the culprit - the cooling system works - just not very efficiently. Running around town temp is 219-222. It's actually gotten worse over the last couple of weeks so I'm glad it is getting some TLC.

I wish there was a sensor to check flow thru the system. I think the next step was going to be checking in/out temps of the radiator and the heater core.

 

I also had the phaser replaced and the coolant changed on my 2017 F150 Lariat 3.5 EcoBoost and have had the higher engine temps since. It gets really high after accelerating/holding boost quickly, then completely letting off, spikes up 230-240 degrees. I have taken it to the dealership several times. They first replaced radiator cap, said not holding pressure, didn't fix the problem. Couple days later I provided video to show exactly what was happening since tech said they couldn't duplicate the problem. Tech drove truck and said he saw 228 but then went down to normal operating temp and that is normal. He said when they did phaser replacement they did pcm update which can make it run hotter. I was told to drive it for a few days and see if anything changes. It didn't and temp reached 247 so took it back. I talked to the service manager this time and he had the shop manager go for a ride so I could show him exactly what was happening. They then said faulty water pump, replaced it and thermostat. This did bring the temps down, but still seeing 220-230 after quick acceleration/boost and letting off, but it quickly drops back down. I have a hard time believing this is normal while not pulling anything. I never reached these temps prior to the phaser replacement. Has anyone found a solution to this problem or confirmed these temps are normal with the pcm update?