brake booster issue

[upchuck]

wondering if my brake issue leads to an obvious diagnosis from those who know.  beyond rotors, calipers, pads, and bleeding, brakes are a black box to me...

where the vac line and check valve meets my booster there is black oil/fluid leaking out.  looks just like engine oil, but how would it get there i wonder.  can brake fluid get black???

not sure if this makes a difference, but this is a booster/brake set up from an 87 gasser jetta with a 1.6na diesel swapped in.  the brakes sometimes do loose power assist, but not too often. 

should i be worried about anything more catastrophic than a rare extra leg workout?  thanks for any help!!!

[theman53]

It uses engine oil to make a vacuum in the vacuum pump. There is probably loose connection or something for it to be getting out. Break fluid will not get out, it will stay in the master cylinder.
You are probably loosing the power assist when the oil is leaking since it isn't making vacuum. It won't hurt anything by leaking...but the extra pedal force on the master cylinder may cause it to leak. I have had 2 break vacuum issues this year and both were followed by replacing the master cylinder. I am thinking that it is related by pedal force. Being that both master cylinders were over 20 years old probably doesn't help much either.

[fatmobile]

That spot is pretty high up on the booster,.. I don't think the booster could get full enough to leak up that high.
 What kind of vacuum pump do you have?
 If it's the diaphram style,.. maybe the check valves are messed up, and the diaphram is busted,.. that might allow black engine oil to make it's way op the hose.
 That's the only way I can think of that oil would come from the vaccum hose.

[R.O.R-2.0]

That spot is pretty high up on the booster,.. I don't think the booster could get full enough to leak up that high.
 What kind of vacuum pump do you have?
 If it's the diaphram style,.. maybe the check valves are messed up, and the diaphram is busted,.. that might allow black engine oil to make it's way op the hose.
 That's the only way I can think of that oil would come from the vaccum hose.

this is what i was thinking too..

[upchuck]

thanks guys.  i see that GAP sells a rebuild kit for "valve type" or "diaphragm type" pumps for mk2 diesels.  i'm not sure what i have, and can't seem to find anything in the bentley.  it did come from an 85 1.6na golf.  i need to do more research.

so if oil gets into the booster, as it appears, could that cause harm?  or should i just worry about check valves and/or the vacuum pump?  sounds like the rebuild is cheap and easy.  but does anyone know of any links to diagrams or rebuild instructions that i could reference?  is the only check valve on the end of the hose at the booster?  or should there be others to check/replace? 

thanks again for all the input!

[theman53]

http://www.vwdiesel.net/forum/index.php?topic=27576.0

I have the old style vac pump rebuild for sale in that thread. The newer style looks like this one on my engine. I don't think they make a rebuild kit for them. If so I couldn't find one. Obviously it is black on my engine, but bigger around and shorter than the diaphram style.