I own a 2006 HR Vacationer diésel with a Cummins 5.9 engine. I purchased it new. It always ran cool on 3/4 mark on my water temp gauge, after 14 years I was told I should replace the coolant and the thermostat, I did and it and has been a nightmare since. When I am going uphill ant the transmission downshifts temperatures climb to overheating on my gauges I immediately slow down and temperature drops to normal within seconds. I took the coach back to the shop that did the work and they said the thermostat was sticking and they put a new one. It is still doing the same thing. Here I am after spending over a thousand dollars on the two visits to this shop still having an issue. The shop is M-Truck Diésel and Radiator in Santee, Ca a reputable shop with excellent reviews, both times I took my coach there they kept over 10 days I am not happy with their service at all. I should have never done that work. If is not Brocken don’t fix it.