Problem with air pack/brake booster

[Tomcat44056]

I’m working on a m35a2 that has been updated with the dual master cylinder an short air packs. It is losing brake fluid through the vent tube that goes from the air pack up into the engine compartment. I would assume that the air pack seals are bad, allowing brake fluid to pass into the air side?

 

[Elk1111]

When mine was doing that I replaced the master cylinder and it stopped.

 

[fleetmech]

If you've got brake fluid coming up/ out of the underhood vent, yes the airpack seals are gone. The pressure developed in the hydraulic portion of the airpack is much higher than the operating air pressure, so when the main shaft seal fails, fluid will work its way into the air side.