2004 6.0. Happened to look down and saw 240 on the temp recently, no other reason to look, all was fine. Mostly I now use my truck to pull my trailer home from where I have to drop it from the motorhome. It's a half mile of a medium hill 13k loaded. The truck will go from 140 to 240 within this half mile. It will reach 208 idling for 30 mins which is not terrible but never did that high before, normally always sat about 188-192

Even when it was at 240 and starting to burp fluid the clutch fan never kicked on. odd
Before I pulled 17k and the clutch fan only kicked on at the top of a few passes, never needed to always towed rather well, under 220 on all but the steepest passes. Highway 207
Replaced water pump that looked good, and thermostat.
Oil and water temps were always within 7-8 degrees.
Inlet and outlet radiator hoses both feel warm, heater blows warm.
have head studs but ya never know. Not sure how a blown head gasket would heat a motor up so fast that is full of water. I'd think it would puke the water before heating up.
No noticeable smoke out of tail pipe,
79k miles
Degas bottle will show 3 psi at bottom of the hill and 14 at the top of the half mile hill, which is fast but the engine temp is also at 240 at that point. (oil is 150)

Any advise where to look next.

 

I had similar problems. I've tried everything for almost two years. Everything indicated head gasket or heads. Coolant pressure 16-18psi, ECT 208°F uphill (heavy camper vehicle)

Done EGR delete, new oil cooler, coolant filter (inline =100% filtration), mechanical fan clutch ( blue cable method also works, but is tedious, as you always have to switch it manually)

Problems solved. Engine runs like a young deer

greetings from Germany