k7jv@arrl.net

We had an exhaust brake on our last Cummins powered motorhome, and we had a similar problem. For us, it turned out that the electrically operated solenoid valve body would stick. It ports air to either the close side or the open side of the exhaust brake valve actuator, which was dual-acting. The solenoid body was an aluminum block perhaps 1 1/4" x 1/2" x 3", and had a two-conductor cable (the actuating power), and three air lines, and had the solenoid mounted on one end. One air line was the air supply, one was to the close side of the actuator, and one was to the open side of the actuator. There was also a small copper colored air filter on the discharge port of the valve body. That valve body can be disassembled and cleaned, and lubricated. I was never happy with the long term success of cleaning and lubricating the valve, but that did solve the problem, for a time, each time. It wasn't terribly difficult to do, and probably took perhaps 20 minutes to do the whole job. And, replacement valve parts can be ordered from PacBrake, and can be found on-line. On our coach, the solenoid valve was located in the engine compartment, and was actually mounted on a light weight metal bracket, located on the left (viewed from the bedroom, looking towards the back of the coach), back and top of the engine. I hope this helps.