How to Fix Leak at Master Cylinder Grommet

[KTPhil]

[pOrk]

It's not just back flow as I understand thats why their's a resivoir, it doesn't leak until I bleed the brakes. Once I bleed the brakes the rubber swells up from pressure and buldges like its ready to push out, and fluid comes out all around the rubber.

[KTPhil]

You should get no pressure after the first few mm of pushrod travel. If you are getting backpressure, the MC seal or bore is damaged and leaking. Time to replce or rebuild the master.

[pOrk]

[KTPhil]

No, but it isn't hard to replace the seals yourself. You just need to be careful with the seal lips and use a lubricant available at your FLAPS. The kits come up on the Samba classifieds and sometimes ebay. FLAPS tend to stay away for liability reasons (stupid as that may be).

[bill may]

[bill may]

i grab grommets from a vw rabbit at the boneyard. they are newer and are genuine vw parts. i also grab the resivoir to use for dual circuit upgrades if using german master. if aftermarket upgrade i use volvo as grommet hole is larger than german.
_________________
Admin note: Bill Passed away - July, 2017

1965 panel bus-Kermit
"Camping is cheaper than therapy"
www.sv2s.com
www.steeringboxscrapers.net
SBS #100
http://www.thesamba.com/vw/forum/viewtopic.php?t=453617

[wardvwracer]

Came across this in researching my problem. Simply, brake fluid is leaking past the rubber plug.

I have a '64 with the single res. style master cylinder. Try as I may, I can't get the stupid thing to stop leaking. I've replaced the rubber plug 3 times and overnight the fluid will be down and the master cylinder is wet around the plug. I can't tell if its leaking at the tube or where the plug and master cylinder join.

Is there any sealer that can be applied that holds up to brake fluid???

I've seen different style of master cylinder on eBay that appears to use a later model plastic inlet. Check it out here:
http://www.ebay.com/itm/Beck-Arnley-072-8024-New-M...27c561aa2b
Anyone ever used one of these? Do they leak???
_________________
David Ward
ACME Berrien Buggy Street/Strip racer build
1963 Single Cab
1969 Beetle Convertible
63 11-Window Kombi Bus
Cornpanzers

[Chris659]

I had the same thing happen with 3 different Brazilian single circuit masters on my 61. I replaced it with a German dual circuit but haven't put the pedals back in yet to bleed brakes.

Would it have anything to do with the rod that connects the pedal to the master? It being too close and not allowing full travel? A mechanic adjusted mine and I don't know where it should be.

Can anyone post a picture of there's? 64 and down and preferably with a dual circuit mc.

I think it's 1mm of travel but where is that measured from?

Also, for those using a German dual circuit master, you can get a German resorvoir from old speed for $45 plus shipping. Fit perfectly and easily! Local vw dealer wanted $120 for the same thing!!!
_________________
61 ragtop, 12 turbo beetle

[Beryl Green]

pOrk "I wouldn't think so as its only for fluid to move from the reservoir to the master, why would it be under pressure? Is there a check valve inside the master that may have failed?"

Have the same problem at present. I'm thinking that maybe the Master has air in it and needs bench bleeding. Air then being pushed through the grommet at the top. Rob and Dave have some good info on Bench bleeding. I'm going to take the fuel tank out so I can do a good steady go at it and bleed the crap out of it with a new German grommet in place. See how it goes. Double checking, am I right, the single port grommet sits a few mm out of the master not flush?

[50Split]

I know this is an old topic, but it came up in my search because I'm having the same problem. After reading I believe I have the cheap plug in my master cylinder. I'm going to order a German plug from Wolfsburg West and I believe this will solve my leak. The first plug was purchased from BAP.
_________________
Quintin - IG @GFK602

[grandpa pete]

If your master is toast I suggest replacing with a 67+ dual unit that doesn't leak
_________________
63 two fold rag
66 sedan delivery Type 6

http://www.thesamba.com/vw/forum/viewtopic.php?t=569619&highlight=sedan+delivery

[50Split]

[vdubmyk]

50Split, I went through the same problem when I redid my brakes. I got a brake set from SoCal Imports and it came with the grommet. Chinese made at best. It leaked no matter what, I live 10 minutes away from them and got another from them. Same thing. Finally I went to wolfsburgwest and picked up two of their German ATE brand grommets just so I can have a spare and it's worked like a charm ever since. That was about 5 years ago. I even found a couple ATE grommets at an estate sale and bought those also. Best .25 cents I've ever spent.
_________________
64 stock bug, 12V (converted 6v unit), 40 hp, all documents even sales contract and dealer window sticker!

[COFFIN]

I haven’t posted here in years and I realize I’m resurrecting an old post BUT, I wanted to share my experience with these master cylinder leaks. I recently replaced a dual mc in my 61 beetle - installing front discs. The rubber seal closest to the pedal assembly leaked all the fluid from that side of the reservoir over night. I twisted and pressed the plastic nipple in and refilled with the same results. SO, I pulled the nipple out and had a look (never a bad idea). These plastic parts have pretty significant CASTING FINS just like a plastic model car kit (I’m sure we all remember that). I carefully scraped w a razor blade and sanded the casting fins off so it was smooth/round and it FIXED the problem. The fins run the length of the part of the nipple that inserts into the rubber seal and fluid leaches out along the casting fins. Sounds a bit far fetched but worked for me. Try that out.

(Somebody smarter than me probably figured that out already)