Bendix Compressor Building Too Much Pressure

[Tomas]

This is on a Bluebird TC1000 bus with the 5.9L cummins and gear driven Bendix compressor.

After identifying several leaks which required both the pressure protection valve at the day tank and the R-12 relay valve to be replaced the system now builds pressure in excess of 145 psi when idling. Both front and rear tank fill up to that level and probably even higher if I don't shut it off. When I drive the bus the pressure drops to around 90-100.

1. I believe the compressor is failing to go into "unload mode" which it should do at 120 psi. Should I go ahead and replace the D-2 governor or should I check something else first?

2. Shouldn't the pressure protection valve in the day tank open before it reaches that high of a pressure?

[Brad_SwiftFur]

Originally Posted by Tomas

This is on a Bluebird TC1000 bus with the 5.9L cummins and gear driven Bendix compressor.

After identifying several leaks which required both the pressure protection valve at the day tank and the R-12 relay valve to be replaced the system now builds pressure in excess of 145 psi when idling. Both front and rear tank fill up to that level and probably even higher if I don't shut it off. When I drive the bus the pressure drops to around 90-100.

1. I believe the compressor is failing to go into "unload mode" which it should do at 120 psi. Should I go ahead and replace the D-2 governor or should I check something else first?

2. Shouldn't the pressure protection valve in the day tank open before it reaches that high of a pressure?

I believe the pressure protection valve "pops" at around 150. (It should be spring loaded and close once pressure drops a bit). Sounds like the governor has indeed failed and needs replaced/rebuilt.

[Booyah45828]

Change the governor.

I've only ever seen a faulty governor cause high pressure issues, never the compressor.

The innards will get gummy from moisture and dirt and cause what you're experiencing. You can take it apart and clean it, they have rebuild/reseal kits for them, but you can find new ones cheap enough that it's usually not worth the trouble.

[Tomas]

Perfect. Thanks both.
New governor on the way.