So here is the story,
2004 6.0 kept loosing coolant under a load. Tracked it down to a cracked radiator.
Replaced radiator with a Mishimoto rad and hoses. Unfortunately I screwed the pooch and forgot to put the clamp on the lower engine hose connector. Blew my coolant and was in an area I could not pull over. Oil temp hit 300f!!!
Realized what I did and put clamp in place. Filled system with water and coolant and things seemed fine. Drove 3 hours in 98f weather. No problems! Picked up a vehicle to tow back (Small MGB) and got 2.5 hours back and started to see a rise in temp (200-220). Now outside temp was 100+. Engine oil temp always stayed within 10 degrees. Got into some uphill grades and temp kept climbing. hit 240 and pulled over when I realized I had low coolant. Had some water and added about a 1.5 gallons and was able to make it home. Never blew the degas cap (new cap by the way), found no evidence of a leak and I have never seen any white smoke out the tail pipe.

Were the hell is it going?
I have read the tech section but since I don't seem to have a tell tail sign of EGR cooler failure or HG failure I am stumped.

Thanks

 

Could be air pocket, but 1.5 gallon is too much for air pocket.

I would still watch out for egr or head gasket. But monitor to see if you still lose coolant. It is not always easy to see coolant from the tail pipe, Too little, you don't see it. Too much, you get hydro locked.

 

Have you pulled the EGR valve to look for signs of coolant in the intake manifold?

 

I pulled and clean the EGR a couple of weeks back. No signs of coolant.

 

Do you have an early or late 04 (ie where is your ICP sensor located)?

 

EGR pulled before or after the low coolant issue?
Have you used a low-pressure gauge to monitor coolant pressure?

With those temps and situations, you are a huge risk for head gaskets and cam failure in the future.

 

2004 June so after the changes.

 

That would mean you have the weaker EGR cooler.

 

Before, but I had a loss from the radiator, maybe both. I had already purchased a low pressure sensor to connect to my CTS3 scanner. Just need to find the time to install.

 

I'd recheck under the EGR valve now. The radiator may have been the "fuse", weaker than the cap.

 

Already contacted a local diesel guy recommended by Sinster Diesel. Going to do a pressure test 1st and then get it to him.

 

Cap hasn't blown off after the rad change but I get your point.

 

I firmly believe that the cap pressure relief set point was, at least in part, intended to protect the radiator. I also believe that the OEM radiator won't stand for much over 15 psi - especially after there is some age on it (ie not much margin for error).

 

The EGR cooler may be the new "fuse" based on service, which is why I thought it should be checked.

 

Yup, and that is why I asked about looking under the EGR valve and then asked about model year. No doubt, with high oil temps (240) and losing coolant, it sure looks possible.