Brake booster issue

A piece of information for the forum. I recently posted about some brake problems I had been having, which many readers and my mechanic assumed, correctly so, that it was my brake booster. What no one could answer for me though, was why my brakes seemed to be dragging after my momentary issue (s). The work was recently completed by TDI Racing and a friend, a mechanic from the local VW dealer, who said that brake booster issues and effects are many, and one of them is that it activates the ABS system. That's why my brakes were dragging, until the computer reset itself.

I don't know about the booster activating the ABS...

But I have had bad boosters that would effectively apply the brakes for you. Could even feel the pedal sink by itself under your foot. Sometimes they don't release, one I had would violently stab the brakes and then pop back to normal operation.

Boosters do some weird stuff when they're not 100% anymore. Some kind of valve in there acts up and causes odd issues like that.

Matt-98AHU said:

I don't know about the booster activating the ABS...

But I have had bad boosters that would effectively apply the brakes for you. Could even feel the pedal sink by itself under your foot. Sometimes they don't release, one I had would violently stab the brakes and then pop back to normal operation.

Boosters do some weird stuff when they're not 100% anymore. Some kind of valve in there acts up and causes odd issues like that.

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That is exactly what the VW mechanic, helping Oliver, said

Oil inside brake booster

https://ibb.co/68P40ct


Can anyone explain how did oil get inside my brake booster?

2003 GOLF ALH.


I have to replace the booster because of that and I don't want the porblem repeating itself.


Any idea would help.

Your vacuum pump is bad.

mine did that
I ended up just giving up on having a booster. Manual brakes on these cars aren't horrible. Could do with a smaller bore master cylinder though.

check valves are letting the vacuum that is in the booster suck oil back up through the vacuum pump after you shut the car off
one of them is in the vacuum pump outlet nipple and can't really be serviced, but the other is in the line from the vacuum pump to the booster, and the third is in the elbow pushed into the booster itself

one option is to tee into the large vacuum line to the booster from this intermediate check valve and add a ported vacuum fitting over to the line running to the airbox, to cause a known vacuum leak there so that the vacuum is broken with clean air rather than oily air after shutdown. It won't affect anything in operation as the ported fittings only have a little tiny hole in them (smaller than 1/16")

cut the hard plastic line off and use 11/32" brake booster hose available at any auto parts store

ETA: you can also pump the brake pedal after shutdown to release the stored vacuum in the booster

oilhammer said:

Your vacuum pump is bad.

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I found oil inside my brake booster vacuum line, and I'm also not getting great vacuum from the connection on the booster line. Do I really need a new pump?

apple4ever said:

I found oil inside my brake booster vacuum line, and I'm also not getting great vacuum from the connection on the booster line. Do I really need a new pump?

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Yes, you do.

I'm havng the same issue with my 2001 jetta alh. Oil is completly filling the vacumm pump and then going into the vacuum line to the brake booster.. Then the vacuum gets depleted very quicly from only 2-3 pushes of the brake pedal and then very slowly rises again to 26-28 in of vacuum. Hopefully a new vacuum pump will fix this issue. Car has 374k miles..

crraig123 said:

I'm havng the same issue with my 2001 jetta alh. Oil is completly filling the vacumm pump and then going into the vacuum line to the brake booster.. Then the vacuum gets depleted very quicly from only 2-3 pushes of the brake pedal and then very slowly rises again to 26-28 in of vacuum. Hopefully a new vacuum pump will fix this issue. Car has 374k miles..

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That's high mileage. My buddy got this new Jetta project with 198k miles on the clock. It may need a new vacuum pump as well. We'll just finish installing the brake pads, wheels and tires on the truck this week before we can take her in.

I put on the new vacuum pump and that fixed my problem.. No more oil In my vacuum lines

crraig123 said:

I put on the new vacuum pump and that fixed my problem.. No more oil In my vacuum lines

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Nice! Sounds like still a pretty reliable ride for its mileage.

[486] said:

ETA: you can also pump the brake pedal after shutdown to release the stored vacuum in the booster

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This is the sort of "duh, *** didn't I think of that?" solution that may do more for me than all the new vacuum hoses and vacuum pump o-rings and JB weld ever have.