2019 F-150 3.5 EB w/Max Tow, 117k mi.

I had a Steelcraft HD bumper installed in January and full RCI armor plating underneath installed in March here. Unfortunately, now when I tow my 5000lb travel trailer here in the hot weather (90+ degrees), I'm seeing overheating.
To address it, so far I've removed the two engine armor plates to rule out the armor plating (plates are still off), had the front grille active shutters replaced, had the thermostat replaced, head gasket was checked, and had the cooling system flushed - still seeing overheating.

Any ideas? I thought maybe the bumper was blocking the intercooler to much, but calling Steelcraft (and searching around online) doesn't really pull up anything about the Steelcraft HD bumper causing overheating on these trucks. I'm not leaking coolant as far as I can tell, and I'm sure the shop would've seen that when they had it while replacing the parts and flushing.

 

Did the shop use a motorcraft thermostat? I recall reading the trucks are tempermental about them.

 

You never mention if this issue ONLY came up after the installation of the bumper and "armor plating". If the truck ran fine and didn't overheat well then...duh...that is the problem. Going and doing all the things you said you did was pretty pointless, IF the truck ran fine before the addition of all the aftermarket parts.

 

The RCI rock armor plating has been removed - it's not that. Nobody online nor Steelcraft themselves are reporting any overheating issues on F-150s with the Ecoboost engines. Very popular bumper - counted a couple dozen trucks with them driving through town this evening, four of them being F-150s, so if this bumper is causing the overheating, that'd be surprising as there are almost no other posts online about this bumper causing cooling issues.
Bumper was installed in January, towed three times ~25 miles or so each and had no issues, but a week and a half ago when I went to tow - overheating.

 

Yes, they installed apparently not just a new Motorcraft thermostat but the entire "thermostat assembly" which includes the housing I guess. They sourced the part from a Ford dealer, and I double-checked - it was a Motorcraft part.

 

I bookmarked this link when I read it to see if others would eventually report the same issue: https://www.f150forum.com/f82/3-5-ec...ot-fix-508337/. No idea how prevalent but you can check it against your truck. If it was this issue then it either came this way from the factory or was introduced when service was done.

 

What were your IATs, transmission temps and coolant temps before, and what are they now during these hot weather tows?

 

Main IAT is between 110 and 140, transmission temp is 185 - 200 (although I was not specifically tracking this temp, so the transmission temp is from a couple point-in-time samples), and coolant temps are 195-205 at idle and into the 240s max while under load (but would likely go higher if I didn't back off when it gets to that point). Outside air temp was 95-105 degrees.

Unfortunately, my only "before" temps would be coolant temps from PRIOR to last summer when I proactively replaced the HL3Z-8525-A thermostat with the updated HL3Z-8525-B thermostat - temps were 220-235 regularly with the A-revision thermostat, towing or not.

 

Is it getting hot, or over heating? Did you get a warning message on your dash?

 

No warning "you are overheating" on the dash, but the temp numbers pop up above the coolant temp gauge - I back it off before I let it get above the low 240s, and this meant barely holding 50mph on the interstate on basically level ground or driving up a few long hills in town. However, a P0217 code is thrown and stored, so the engine is reporting an overheat condition to my code reader.