Fan Belts Check Valve

[cmillsap]

After a few days of my coach sitting, the mini air bags on the fan gearbox would slowly deflate causing the 3 fan drive belts to become slacken. This made it easy to throw a fan belt when starting the engine. To lower the chances of that happening, I would wait until my Prevost auxiliary air gage was at 60 psi or more before I would put the engine on high-idle as I built system air pressure.

A common reason this happens is because the check valve in the air supply line feeding the mini air bags is no longer working properly. To solve the problem, when I was at Prevost having my bus serviced, I had them install a new check valve in the air line.

In the engine compartment and directly behind the belt tensioner knob is the air pressure regulator valve. The check valve is located on the air inlet side of the pressure regulator valve. It should be, if original, a 1/8" MNPT x 1/8" MNPT that should cost less than $20 or you can get one from Prevost for about $49.