1978 Bus Brake Servo

[cjacaruso]

Hello. I have a 1978 bus which has been having issues with the brakes for basically 20 years. The brake system is pretty much stock with ATE front calipers. Currently the front disc brakes drag a bit and generally slow the bus down and cause the engine to run a bit hot. I have replaced brake lines (flexible), rebuilt front calipers, replace rear cylinders, replace master cylinder, bled all brakes multiple times. Still has dragging brakes but much better. They used to practically lock up and would slowly release if the vehicle sat for 5 minutes. I recently was advised to disconnect the brake booster to see if that fixed it. It did. So the culprit is the brake booster which was purchased new from Wolfsburg West (WW) in 2016. Of course, it takes much more force to stop the bus but the engine is happy! So I just recently purchased a rebuilt ATE servo and am connecting it. The old servo (WW) has a small "pipe" coming out of the back of the servo by the master cylinder where the vacuum line runs to the engine in the back. The rebuilt servo I am putting in the vehicle has no "pipe", but a hole with a rubber piece for sealing a piece which I am guessing is used to go between the servo and the vacuum line. It looks a lot like a check valve could go in here. I already have a check valve in the engine compartment. Should there be two check valves, one at each end? Should the check valve be in front at the servo and no check valve in the engine compartment. Should there be some kind of adapter piece which goes between the servo and vacuum line and if so, what? Lastly, the old, WW, servo had a bunch of brake fluid inside of it when I removed it. I'm pretty sure that shouldn't have happened but what does that indicate? Let me know if you have any info. Thanks so much!