Same issue here. Mine has been pressure tested twice in the past 10 months. No leak, but both times the cap to the degas bottle was missing. Some how its popping off and allowing vapor to escape. Hope this helps someone out there.

BTW I'm driving a 08 F-250 CC Lariat 6.4L Diesel.

 

This has been happening to me as well. I've been pulling my 5'ver alot in the past 3 weeks. After the first pull I checked my coolant and the cap to the degas bottle was sitting on the battery and the coolant level was low. Scratched my head, topped it off and put the cap back on. The 2nd pull, degas coolant level was below fill line again. Topped it back off. 3rd pull, coolant level dropped to 2nd fill line but not below. 4th and 5th pull, same thing. I don't know where it's going either. I'm wondering if it's pucking out of the cap because there's a white residue around the top of the degas bottle.

 

Mine had white residue on the bottle after long uphill pulls with travel trailer in tow and my HG's were leaking causing the pressure in the bottle to burp out coolant.Replace HG's and installed ARE stud's and works awesome now.

 

Head gaskets were leaking? But not blown? Just needed bolts replaced? How the heck did you figure that out?

 

Whew, thanks for replying StanleyZ. I was kinda scratching my head and didn't know how to reply.

 

Mine would only puke coolant after a long (maybe 3-5 mile)uphill pull with TT hooked up,The rest of the time it didn't do it.The dealership here hooked up all their test equip and we made the same pull where it did it every time and it would pressurize and puke out coolant.Replaced the HG's and installed the ARP stud's(stud's my expense 500.00) and works awesome.

 

OK, I guess they have something beyound a compression check to figure it out. we had a thread on here the other day from a guy that was saying the 6.4Ls were blowing HGs. But yurs wasn't blown the heads were just "loose" for lack of a better term, right? No coolant in oil or oil in coolant or loss of compression on adjacent cylinders? just a puke on hard pulls. I'm gonna remember that cause it's gonna come up again and somebody will think I'm smart as all getout when I tell them to check for loose heads.

 

Very unusual indeed.

 

Your right! I had no coolant in the oil or visaversa. I looked at
the Hg's when it was apart and you could not see any sign of blown out portion or burn't around the combustion chamber area.Tech said under load with the heat he has seen a few do this.Seemed to be when temps climbed to 220 deg and pulling a load and long uphill pull 15-35 mph constant.Don't know if the studs stretching or what?Maybe Senix could shed more light on this.I think the new 6.7 has 5 studs per cylinder so that should keep the heads from moving.I had 2 friends with 6.0's that did this and thought the 6.4 had larger studs than the 6.0.

 

My thoughts on the HG failure for Basshunter (which does not amount to a whole lot ).

First under the conditions of a hard pull at WOT or close to it, with the temps that are produced create and excellent seal of the piston rings. As an example, my summer trip last year pulling out to colorado and back, over 5K on the oil, regens around every 130 miles, GCVWR of 23K going out and 22K coming back... I had .5% fuel dillution. Absolutely no coolant.

So I think the same will hold true here. An excellant seal for the bottom end. I would imagine, even though none was reported I would bet there you were eating a little coolant during the hard run.

I have seen cross contaimination into the cooling system before, usually on a gas motor and due to an overheat event. Highly unusual to only have it during a heavy boost condition in this motor but I can see it happen.

Head studs on this motor are M16 vs M14 for the 6.0. In addition, they are not required to hold the rocker arms so that means they have only one job vs too and are thicker.

So I think the short run and catching it early resulted in not producing the tell tale signs on the HG's.

 

Imagine that, head studs with nothing to do but hold the head down. Just like my 49 ford I had in high school.

 

I think you mean the rocker boxes on the 6.0 not the rocker arms.

 

Actually I think the technical name they are using is rocker carrier. Point is that was not the best design.

 

I know that the ARP stud's we put back in were torqued to 325 ft lbs.Hope that holds them heads down! I know the mechanic said he usually breaks 1 snap-on socket per stud kit torqueing them down.

 

Well got the truck back yesterday with a brand new radiator. This makes the 3rd radiator to be in this truck the first one was replaced shortly after the guy who had the truck before me drove it off the lot. According to tech at dealership ford determined that after some time the coolant becomes acidic and the water pump pumping at such a high rate causes coolant to eat through radiators. He also told me that for the 2011 they now have a check coolant light that comes on and lets them know to check both acid level and strength of coolant about every 7500 miles.

Also no more exhaust smell in the cab, found an exhaust leak behind turbo (had to pull cab) luckily that was under warranty...Just thought I would update as to what they found out. Thanks guys for all the input.