turbo, engine brake, or fan noise?

[dirt01]

I have a 2003 F350 with a 6.0L. My truck runs fine with no noise during normal driving. When I hook up to my fifth wheel I get a sound that surges up and down. It sounds very similar to when the engine braking is working, but it roars up and down over and over. I can back out of the throttle and it will stop until I have to give it some throttle again. I have had the fan replaced and supposedly checked at the local ford dealership. The truck does not get any hotter than normal. The oil pressure stays exactly the same. The RPM doesn't change as if the motor was reving up or the transmission was slipping. I have no idea where to start and don't have the money to go to the dealer to let them start replacing parts until they figure it out. My truck has new injectors and has @ 187,000 miles on it. Everything is completely stock. No programmer etc... If someone can steer me in the right direction on how to isolate the problem I would greatly appreciate it. This is my first diesel. I have had gas burner (V10) super duty in the past.

 

[JRJ04]

This sounds completely normal. This is more than likely your fan clutch engaging to keep the motor cool with it being under load. It will periodically engage/disengate to different degrees depending on load, engine temp, oil temp, ambient temp etc.

I'd keep driving it!

 

[jherman]

Are you seeing any coolant loss? In other words are you adding coolant but not seeing any leaks anywhere, is it just disappearing.

I ask because a fella told me that his clutch fan was engaging all the time and it happened to coincide with an EGR and oil cooler plugged failure. He put a delete on and everything was back to normal.

This is just a suggestion not a rumor to start.