I just finished a 2170 mi round trip across the south pulling a 13k 5er with 100 deg temps being the norm. The only problem I had with my 6.4 was the temp indicator spiked three times and a "Reduce Engine Speed" warning flashed. I pulled over and stopped and immediately everything returned to normal all three times. Anybody experience this besides me? I had a reply on the Towing section that suggested it could be a temp sensor or fan clutch. As a matter of fact I never heard it rev up so that actually makes sense.
Any clues?

 

Have you checked for trouble codes? I think if the fan wasn't functioning properly you should get some codes.

 

It started doing this over the weekend...of course...and I work in a relatively "dealer-free" zone of So TX. So no I haven't had it checked and no codes are popping up on my dash warning light.

 

Hmm sticking thermostats? Have you ever cleaned and degreased the rad fins? You'd be surprised how much build up gets in those fins and reduces the cooling efficiency. Also check your fan connector on top of the fan shroud to make sure it's tight.

 

I need to do that. It was just odd that an immediate spike, like flipping a switch would happen.
Then return to normal when I slowed to a crawl, and then continued on my trip at 60-65 mph.

 

Get yourself a Scangauge II from Autozone or another local place that carries them, install it and programm the Xgauge for the 6.4 (see the Scangauge site).

The dash temp indicators are little more than idiot lights and do not display proportional to the actual temperature. With the SG you can monitor the actual coolant, oil and trans fluid temps and see what is really happening.

You should also monitor the DPF temp as that will show you when it's in regen and you should avoid interrupting regens if at all possible, or at least high idle after parking until the temp comes down to 600 or so before shutting down.

 

Thanks for the scan info.
DPF temps are no longer an issue😁

 

After a few months here's an update:
While prepping for a 1700 mi trip I decided to give the temp issue another look. One of my son's old high school buddies is a sho-nuf duramax tech with a good friend that's a Powerstroke tech. After a lot of texting the fix was diagnosed as electrical, prob a temp sensor, about $14 worth. Hmmmm sounds cheap. Problem is getting to it, so while apart I decided to do the temp sensor, thermostats, radiator hoses (now redesigned w two o-rings per end instead of one),a new radiator cap, new fluid, 7.9 hrs of labor and I was ready to roll. Son-of-a-gun, it worked. I'm not 100% sure whether it was any one thing or the combo, but so far it has worked. East TX to Mobile and back w/ no issues pulling my 13k+ fifth wheel.
Thanks for all of y'all's suggestions, it's deeply appreciated.

Now about the trans that's slow to shift into first, grrrrrrrrr.

 

Glad to hear you got it fixed, and thanks for the update!