[Rich Biebel]

The belt on most of those QD 7500's is the water pump drive belt. It has no adjustment. The sheet metal covers need to be removed and in motorhomes that often means the unit has to come out. Since there is no adjustment.....the water pump pulley must be removed to remove and replace the belt. The fit has to be reasonably tight so the right belt is important. The belts crack and if it is not changed could break and the unit will obviously overheat. I usually change the t-stat and temp sensor at the same time. Deposits build up on the sensor and they can cause poor cold starts and random shutdowns. The sensor signals the controller by way of an ohm reading what the coolant temp is and this controls the glow plug operation....If the unit is cold....the glow plugs are powered before cranking.If it is warm they do not energize.