I have a 550 6.7, has about 49,000 miles on it. I've had this problem I think for a while now, have had it checked out several times at the dealership. When I'm pulling my trailers empty or loaded, cold, or hot, but more when warmer my truck temp. goes from normal 3/8 to 3/4 or so. Now here is the weird thing, it does it mainly in 5th gear, and sometimes 4th and 6th. I'll be going up a grade small or big and it downshifts into 5th, and shortly thereafter the temp. gauge starts to rise and goes to 3/4 or so, then when it shifts into sixth it will fall back down to normal within seconds. Keep in mind my rpm's can be around 2000 or so for this to happen. This is my 4th truck since 04', started with 04' 350 cc, 06' 350 cc, 08' 350 cc, all these trucks had the same equipped bed, and pulled the same trailers with me driving, so nothing changed and never had this issue with any of the other trucks. Anyone else out there experiencing this, if so your input would be greatly appreciated. Thanks.

 

Do you hear the clutch fan kick in?

 

Oh yeah, we already blew one apart last summer, going down a grade with a load and was already running then it downshifted and it flew apart, messed up the radiator, had to be replaced. Ford said its designed to not do that but idk, it happended to me.

 

Something's not right here, you engine should have no trouble keeping cool even under heavy load. I believe the cooling system is the same on your truck as it is with the pickup truck models, and those are running 100 HP more than yours is. Heat production is related to horsepower output, and lots of guys are dragging big weight up steep hills at WOT without any overheating issues.

I'm thinking you may have a stuck thermostat that would restrict coolant flow to the radiator.

Do you have the LCD "Productivity screen"? If so, what do your oil temps do when this happens?

 

My truck is doing same thing. They have replaced thermostat and air charge sensor but it's still heating up under load climbing! I never had that issue until the last update was done. So if you find out the problem please let me know. My warranty is up in November so I would really like it fixed before then

 

Did they ever test the clutch fan? Has the water pump been looked at?

 

There are actually 2 thermostats on the Pri. cooling so it could be one of those partially or totally hung up. They are staggered by about 5 degrees in opening temps.

 

They said water pump and fan clutch tested fine. But something is definitely wrong because I use to pull vail and Eisenhower with no problems

 

They replaced the thermostat on motor which they said that was the only ones it had but according to the net it has four thermostats total.

 

Sorry I replied to some of your posts I am having the same exact issue with my 350 it's been in shop three times for it and last time they replaced thermostat and air charge sensor but it's still having the same problem. My didn't notice this problem until after the last update did yours do the same thing? It's the update that tells when dpf is finished with its cycle.

 

I can pull Eisenhower at 55 mph, GCVWR of 25K with my '13.


Two thermostats for the primary (engine) is correct. They are not thinking secondary.


So the secondary system, how is the coolant level there?

 

Have you found the issue yet? Mine is doing the same thing.

 

The last time my truck was in the shop we let it idle for an hour then climbed Rio Blanco and at the top the fan clutch started acting up so they changed it. The last time I went up it the truck heated up again with an 8k camper. The only other thing I can think of is water pump. It's getting so old having this problem. I'm just about to trade the truck off! Whenever I go to buy my next truck I'm test driving it with trailer attached!

 

have you checked the rad/coolant tank cap and the tank itself? cap could be leaking pressure.. or tank could have a hairline crack somewhere..a diesel engine should not overheat..

 

no I haven't I'll check it tomorrow thank you