Bd Brake Question???

[RON'S RAM]

Does anyone out there know if the BD Brake is spring loaded to the open position? If so, I may have a broken spring. I've been having problems with the brake going on while driving, and with both vacuum lines disconnected, the brake stays on. There are two vacuum lines, so I'm guessing one is to open, and one is to close the brake. Are Pacbrake, or Jacobs brakes spring loaded to open if no vacuum present. Towing camper tomorrow, hoping to fix it. Thanks, RON

 

[Evan A. Beck]

The BD brake is not spring loaded when open or closed. It uses vacuum on either side of the piston to actuate the brake. The only spring in it is the 60# regulating spring, to prevent excessive exhaust backpressure.



The Jacobs brake is spring loaded in the open position, but the PacBrake is the same as the BD one. Only difference is in how they are regulated.



Check your spool valve, as I have seen them stick in one position or the other. A little air tool oil works wonders for increasing the longeveity of the valve.

 

[RON'S RAM]

Thanks Evan;

I took the spool valve off the truck tonight, and checked it out. Everything seems ok. The spool moves nice and free, no moisture or sediment in it. Looks like as long as the engine is running, and the vacuum hoses are connected, there is always vacuum at the exhaust brake. With the power switch off, vacuum is on the top side of the brake, holding it open. Seems simple enough, so I don't know how the brake would come on while driving. I'll try it again tomorrow and see what happens.

 

[Runaway]

Throttle Switch

Ron, maybe the throttle switch came out of adjustment! Just a thought.