Water in the brake servo unit!

[analord]

Hi all,

I've just taken the brake servo unit off the bus during a braking fault diagnosis (Pedal not retracting fully then pedal 'undulates' under throttle/increased engine speed influence), and noticed a substantial amount of rusty water poured out from the diaphragm unit as it was removed. I cant think of where any water would come from, aside from any the input pipes. All rubber boots and seals are in excellent order, and the servo is 15 months old (ATE).

Any ideas?

Thanks

 

[Araon]

good seal on the resevoir? remember brake fluid absorbs water from the environment

 

[analord]

reservoir is fine and there should not be any brake fluid in the servo unit anyway as it works within a vaccuum??

there is a long pip that runs to the back of the engine bay so i may check that for signes of leakage.

 

[Araon]

You know for some bizarre reason I read that as Master Cylinder :? dimentia's creeping in......

 

[Trikky2]

Which side of the diaphragm was the water?

If its behind (on the vac side) then check for leaks since the constant vac when running can suck moisture in, which will build up over time.

If its in front, the breather pipe that lets air into the front of the servo (think it goes up into the body by the arch) is where there might be water ingress.

Check for leaks, loose joints, cracks.

If theres no fault found then the only other way would be if the vehicle has been through some deep water.