TheSamba.com :: View topic - How to Fix Leak at Master Cylinder Grommet

Sat Aug 19, 2006 7:10 pm

i have just completely replace all the brakes on my 1964 beetle pan. i have bleed them and fixed all of the little leaks that can happen when you replace everything. so in theory there should be no leak but i am not that lucky. i can't get the resevoir to stop leaking. i have gotten the new little grommet and gotten the new line that is suppose to run into it and everything has hose clamps on it but still over night my resevoir will be drained by the time i wake up the next day. i was looking in the Wolfsburg West catalog and it shows a little washer that i guess is rubber going into the master before the grommet. does anyone know what i am talking about? anyone have any ideas? i really want to get my car on the road but i dont want to have to stop with the e-brake. thanks for any help

Sat Aug 19, 2006 8:33 pm

Is the ruber gromet all the way in and snug? When i replaced my master cylender i messed up the gromet and had to replace it. I all most riped it in two trying to get it in. In the bentley manual it only shows a ruber gromet at the master cylender. At the reservor it shows a ruber insert were the line enters the reseroir. Id check for cracks in the resevor also. Good luck.
Brian

Sat Aug 19, 2006 8:40 pm

i have replaced the resevoir and the line that goes to that grommet. i acutally bought two grommets for some reason and the first new i put in i took out thinking that maybe it was ripped and the one in there now i made sure not to mess it up but it still seems loose. that is why i am asking if there is another little piece of something that goes down in there to make the seal tighter. thanks ya'lls replies

Sun Aug 20, 2006 4:14 am

It sounds like you may have the grommets for the dual master cylinder, I have't physically compared them but they are a different part number.
The fact that you ended up with two grommets makes this scenario seem likely.
Hope this helps...

Sun Aug 20, 2006 9:35 am

GregZA wrote: It sounds like you may have the grommets for the dual master cylinder, I have't physically compared them but they are a different part number.
The fact that you ended up with two grommets makes this scenario seem likely.
Hope this helps...

Sounds possible. The early grommet is a snug fit into the m/c, then once the res line is in, it won't leak, the later one has a larger inside diameter, and would pour out badly...you shouldn't need any hose clamps either. The brake fluid isn't under any pressure from the res., just gravity.

Find your old original grommet, and compare to the new ones.

Mon Aug 21, 2006 10:02 am

Get the right part number. I bought a few lately and they were like 95 cents apiece.

It's a tough place to work in, but make sure that any rust that may have formed on the lip of the master where the rubber goes in has been wiped off. Brake fluid absorbs moisture and this is a prime place for rust to form. I did this on my '63 last month after getting tired of filling the resevoir every couple of weeks.

Also it seems that any little bump or twist that happens to the feed line, like replacing a portion of it, always breaks the seal around the lip and causes the leak.

Tue Aug 22, 2006 12:45 pm

yeah any movement on that thing lets fluid out. it just seems to me like there is something else to make it seal better. i saw a washer in the wolfburg west catalog blow up diagram. it has no part number and its not mentioned but there is certainly one in the picture. i think i am going to try that. it should leak and it makes me mad cause it is messing my paint up. i have spent a year cleaning just the pan and now that whole section is ruined. does POR-15 stand up to brake fluid? the next pan i do is not going to have this problem. there has to be a way to keep the thing from leaking. people drove them for 40 years with out problems right??

Tue Aug 22, 2006 12:47 pm

Check Bentley and other diagrams. Some years had a washer under the grommet on ONE of the pipes (but not both). It might be needed for the grommet to fit sungly.

Tue Aug 22, 2006 1:32 pm

I thought that the flat metal washer (with a somewhat oblong hole) was to act as a "spacer" to keep the grommet from forcing down and interferring with the small port that lets fluid into the piston area of the master cylinder? It seems that Bentley discussed this...at least in the 1200 manual.

L572

Tue Aug 22, 2006 1:57 pm

Not sure, but a late T3 dual cylinder had only one washer among the two ports.

Tue Aug 22, 2006 2:26 pm

cool well i am glad that other people know about the washer thing. i think i am going to try that. i think that with more pressure on the grommet it would fit more snug. the inlet tube doesnt leak its just around the outside so think the washer is the next step. if it doesnt work i'll let folks know. this thing is so anoying.

Sat Jun 13, 2009 4:34 pm

I am having the same issue with my grommet leaking on my new dual circuit master cylinder. The front one is not leaking but the back one leaks. I even replaced the grommet from another master cylinder I had and it still leaks. The grommet doesn't fit super tight, it is just snug. Is there anything I can put along the edge that will seal the brake fluid and stop it from leaking? thanks for help.

Sat Jun 13, 2009 9:02 pm

i am putting brakes all around on my 65 and let me tell you that rubber grommet i hate that *)#king thing

Sun Jun 14, 2009 6:23 pm

vdubtt wrote: i am putting brakes all around on my 65 and let me tell you that rubber grommet i hate that *)#king thing Yea tell me about it..so how do you prevent it from leaking?

Mon Jun 15, 2009 5:19 am

Off topic, but I went through three master cylinders for my '94 Suburban, just for the grommets leaking until I got a good one. They were lifetime guarantee units, last one I could live with the rate of leakage, but swapped it out when I did the brake booster. Those grommets were NOT available by themselves, even at the dealer, and I believe the rubber/plastic was simply not flexible enough. On those units the reservoir is attached to the MC when you buy it, so this was from nothing I did; radio mechanic (no, not the PBS guys), said he asked his shop mechanics and none had EVER observed a leak there....go figure.

As to VW, I once got a rebuilt MC for mine, and the plastic elbow was what was leaking, cracked, had to swap that out.

Mon Jun 15, 2009 5:38 am

I hear ya on the plastic elbow..has anyone ever tapped the hole and put a metal fitting in there or metal elbow for the hose to slide onto? thx

Tue Jun 16, 2009 9:12 pm

I had this exact problem with my 66 single circuit. I went through 5 sets of plugs before I got it straightened out.

Here's the deal: The plugs that work are from Germany: The rubber is soft and the shape of the plug exactly matches the retaining grooves in the Master Cylinder.

The crappy ones are from Brazil (and now, probably China): The rubber is hard as a rock and the mold work on the retaining end of the plug is "primitive" and does not conform to the M.C -- hence the leaking.

Call Wolfsburg West and talk to them... that's where I got my info and my German made plugs. Tell them the situation and ask if they have the German made plugs. I have not had to replace my plug in years since I got the German make.

Sat May 21, 2011 6:55 am

I have the same problem with my single, I replaced the rubber and bled the brakes and had GREAT pedal feel and and all that. After about 5 minutes I checked it and sure enough its leaking again, and the rubber feels like its under pressure. Its soft and moves around before bleeding the brakes, but once the brakes are bled it looks like its trying to pop out of the master and hard as hell to move. Is there supposed to be pressure behind these boots? 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?

Sat May 21, 2011 8:44 am

If that grommet is under pressure, you have a clog somewhere between there and the reservior cap bleed hole, which I doubt.

Sat May 21, 2011 11:10 am

KTPhil wrote: If that grommet is under pressure, you have a clog somewhere between there and the reservior cap bleed hole, which I doubt.
Why would that cause pressure under the rubber boot though?

Is it a fair assumption that the master is toast?