I used the term boiling to describe what it looks like. It was not boiling from heat. I have never seen any engine/vehicle that did this, and evidently I have never opened the rear access door while the engine was running.
I talked to the service dept at two different International dealers and the mobile tech who came to work on it, and none of them thought this normal? Seeing this and the fact that it had no power, I thought I had a serious issue. When I did some research, it appeared that the EGR cooler or the air compressor (liquid cooled) was leaking pressure into the cooling system and pressurizing the coolant tank.
Utube videos of coolant tank boiling, bubbling, churning on Navistar and Cumins engines was diagnosed as either EGR cooler leaking or a blown head gasket being the cause.
After noticing that the turbo boost pressure was low when I tried to climb the hill in my driveway, I changed out the secondary fuel filter and cleaned out the pump screen. That restored the power issue to normal.
The mobile tech, who wasn't very experienced with Maxforce 10 engines, decided to pull the EGR valve to check for moisture in the EGR cooler without the proper puller. In doing so he broke the EGR valve with it partially out out of the housing. He showed up this morning with a new EGR valve ($714) and the correct puller. He also talked to a coworker who appears to be only Maxforce mech that knew that the coolant tank flow was indeed normal. So, the old EGR valve was removed without damaging the housing and a new one installed. He also got in trouble with his boss for working on an RV and was told to get through with it. They told me on the phone that they do not work on RVs, but when I asked about a mobile mech, the gladly provided his name and number??
Just took a 20 mile test drive and it appears that everything is working fine. This took one week to get resolved. Sure glad I wasn't on the side of the road and I'm glad this ordeal is over!
Randy and Laura
2012 Monaco Knight 36PFT
2016 Jeep Wrangler Rubicon