Hello all - just to throw in my 0.02.
We own a 'new to us' 2008 Winnebago Journey with the 6.7L ISB EPA07 350hp engine and 55k miles on ISC rear-radiator chassis.
The previous owner had Freightliner replace the fan clutch due to all of the above symptoms before we purchased the rig.
We began experiencing the same tendency to overheat (although I never actually let it overheat - just watched the gauges perform EXACTLY as described). First I verified cleanliness of radiator and CAC and so on - all was well.
Cutting to the chase...I just returned from Camp Freightliner in Gaffney where their service department took a look. They suggested installing a "Guard Dog" instead of replacing the clutch, as the clutch itself is new (within 2 years) and there are no oil leaks, signs of slippage, etc.
The Guard Dog is a sort of override fan controller and is a small box that clips in to the harness that drives the fan.
Problem solved. Zero overheating and the fan cycles up and down as appropriate (like it should have in the first place). Cost for Guard Dog was $300.00. The Guard Dog is a product made by Horton
Horton Vehicle Products | Horton
I gave the techs at FL in Gaffney the SS Code 3737 and we discussed everything from just pull the fuse and leave the fan locked all the time, to replace the fan clutch, to a direct-drive solution.
Time will tell if I made the right decision, but at $300.00 it was a risk I was willing to take starting low and going slow versus yet another fan clutch still to have issues remain.
So far 3000k miles home and zero problems the entire return trip over 2 weeks.
Just to share my experiences. I'll post again if the 'fix' doesn't hold!!