Has anyone experienced coolant being pumped into the overflow tank (and then overboard) while under load? HAppens only when towing my 10,800lb 5th wheel. Could it be combustion gasses leaking past the head gasket into the block, putting more pressure in the system than normal? The rad, t-stat, fan clutch are all new.
Appreciate any help on this, thanks

 

I think you made the diagnosis, head gasket.
Heavy fuel and higher boost means higher raised combustion pressure. The easiest path is either between cylinders or into a coolant passage.
Any black blobs (oil) floating in the overflow bottle?

 

Mine's doing the same thing, anything over like 20lbs makes all my af blow out,,,,fun stuff. Guess it's time for studs and some O-rings. Sad part is , I did the hg less than 10k miles ago :-\ Should've done the studs and O-rings then.

 

Smokin;

Being yours is a recent repeat, I would completely check the head for cracks

I didn't go with o-rings, but did opt for studs after seeing a brand new Cummins head bolt from a prior day head gasket job.

 

Sure sounds like the head gasket or a cracked head. I had an 04 that had blown one, and no oil or fuel in the coolant, it just blew it out the over flow like mad. The head had cracks between the exhaust valves of 2 cylinders along with the blown headgasket between 2 cylinders.

 

well the machine shop that true'd the head SAID they magnafluxed it,,,,but we have issues with them (we being me). So who knows what they actually did and what they just threw on the bill. I've been contemplating throwing a 24v head on,,,so I dunno,,,I might get it magnafluxed again, but if it's cracked, I might as well go 24v huh? I DEFINATELY will do o-rings and studs next time though.