05 ambassador cummins engine temp hot

I must address the "burp" the cooling system fallacy. All of the modern engines have a pressurized expansion tank. This tank should sit higher than the highest point in the engine. If it does not the RV manufacturer screwed up. There are usually 3 hoses to the tank: the main feed (my Cummins went to the lower rad. hose), the overflow and the bleed hose. The bleed hose attaches to the highest point in the engine cooling system so any air will travel to the expansion tank. Any vehicle equipped with an expansion tank, not an overflow tank, requires that you fill the system, pressure test it, put the cap on and run the engine. As air moves to the ET the level may fall but if you pressurized the system this will not occur. When you pressure test the system you will feel, the amount of time it takes to reach pressure, any air in the system. When you release the pressure any air will usually move to the ET. Top off the ET and let it run. Make sure you have the heater valve open.
Randy