I have a 2006 Cummins 400 ISL on a Spartan Chassis. The engine warning/alarm to shut down the engine comes on at 230 degrees for me which has happen several times. However, three times in the last year the heat was so great it blew a hole in my heater hose, lost all my coolant, and left me stranded on the side of the road (Tennessee, New Mexico, and Texas) waiting for mobile diesel mechanics. Each time I replaced the entire heater hose with very high quality hose, but it still kept happening. My service center finally determined the problem. It's a design flaw and a Cummins campaign item. Cummins changed the design in 2006 to where the hose coming right off the block is right next to the Turbo. They welded a piece of pipe coming off the engine block to re-route the hose and I have now had no more problems.
Additionally, FYI, another Cummins campaign item is the fuel hose to the fuel rail on the pressure side. Another design flaw with numerous coomplaints and failures. Due to vibration the part will rupture right where it enter the rails and start spraying fuel (about 5 feet) out of the back of your coach. It's a real fire hazard. Cummins has redesigned this part and will replace it at no charge if your engine is still under there 5 year warranty, after that, you have to pay for it. And yes, this just happened to me on my last trip and Coach-Net had me towed 98 miles to the nearest Cummins Service Center. I love Coach-Net.
Hope this helps.
Brett Davis
