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Do people find the arrangement for getting brake fluid into the master cylinder where the tube is just poked into a rubber bung is problematic? Mine leaks.



I am surprised that the inlet pipe is not held in place with a threaded union like most other master cylinders.

Does anyone have a brand name and model number for the master cylinder as I might try locally to see if I can get a new rubber bung.

Thanks

Garry

Hi Garry,
The master cylinder for a Type 1 VW is nearly the same but have an extra outlet that must be closed with a threaded plug. The master cylinders are not normally supplied with the rubber fitting nor with the slotted washer that sits beneath the rubber fitting. It appears in the photo that your brake line is entering the fitting at a very sharp angle which may be causing the leak to occur. The line should enter very straight (perpendicular to the top of the rubber face. Bend the line in a shape which resembles a question mark"?". This should solve your problem unless the rubber is cracked.
Cheers,
Steve

Thanks Steve - I have ordered a new rubber bung from the Uk - much cheaper than local. I was thinking that the pipe was going in at the wrong angle so I will pull it out and bend it so it comes in vertically from the top.

Cheers

Garry

I pulled the pipe out and tried to bend it to the correct angle but it was work hardened and cracked. Thankfully there is enough pipe to remake the bend so I annealed the metal with a gas torch, put a new flare on the end and re-bent the pipe. The rubber bung is in Ok condition so I put it all back together and while it was still dry put some sealant around the top where the pipe goes into the bung.

I will see how it has all gone tomorrow but I have to admit I am not happy about the design aspect of this part of the braking system. If the leak persists I think I will pull the master cylinder out and get a brass adapter inserted where the rubber bung is so that an normal brake connector can be used.

Garry

I left the bung in place with some sealant around the top sit overnight to set. Went for a nice bouncy drive yesterday and it all survived with no new leaks developing - so it seams all is now OK. All the little issues with the Haffie are slowly being sorted.

Garry

I'm having a similar problem. I have a fairly new VW master cylinder, a new rubber bung and a new brake pipe, but for the life of me can't stop brake fluid from weeping out from between the grommet and the cylinder. Nothing comes out between the grommet and the pipe.

We have tried to ensure that the brake pipe goes in at right angles, and have also used a suitable (grease / oil resistant) silicon sealant, but it still weeps

Any suggestions from anyone? Desperate to get this sorted, as when done my restoration will be as good as complete!

TIA

Wrap it with Teflon tape?

Julian,

If the rubber is leaking round the outside where is touches the mater cylinder, I assume you have made sure that all the surfaces where the rubber touches are 100% clean and do not have any bumps / lumps / troughs etc that might change the shape of the rubber bung? Do you have to apply any force to get the rubber bung (with the pipe in place) to fit into the hole in the master cylinder?

There should be a ridge round the inside edge of the master cylinder and a corresponding trough on the rubber bung and to have to get the rubber bung in deep enough for the ridge and trough to snap in to place.

John

The bung is new and clean, as is the receiving hole in the master cylinder. We had to fit the bung into the MS before inserting the pipe as otherwise it is such a tight fit that it would have been all but impossible to get the bing into the hole.

There is a ridge towards the bottom of the hole which one might like to think that the bung is supposed to go past and then self secure on this ridge, but a) there is no corresponding groove in the bung, and b) we couldn't get the bung to go that deep anyway. (It seems to sit slightly proud of the cylinder)

There is a ridge right at the top on my VW replacement master cylinder which is why I was asking. I wonder if you had fitted the pipe first and then just "pressed" the bung into place, maybe with the help of a suitable tool like an open end spanner applied enough pressure to force the bung and pipe into place.
John

Hi Julian - as above I was able to seal mine but it is a Haffie master. Absolutely woeful design - I even contemplated taking my master cylinder out and getting it drilled and tapped so that a screw in fitting could be used - like it should have had in the first place.

I guess the obvious - is if the hole is different in the VW master vs the Haffie Master - will a VW bung fit better.

As I think this is a design disaster but mine still does not leak but I am sure I will have the same problem if I have to pull mine out in the future.

I feel your pain - and hope you can resolve this easily.

Garry

Hi Julian & Garry,

I got a master cylinder from NAPA for a 1965 VW Beetle. The MC was made by FTE in Germany and it included a stop light switch and threaded brass plug for the extra hole at the back. I think the cost 5 years ago was $29.95 CDN. I used the rubber "bung" that is original to my Haffy and everything worked perfectly and have not had any leaks. Note that the rubber bung is a very tight fit and it takes some effort to insert in the MC receptacle. A photo of the FTE label is below for those looking for ordering details.

For those who question the integrity of this design, it has been used for decades on millions of vehicles and is still in use on some modern models. If you have ever tried to remove a threaded fitting from an old corroded and mud encrusted master cylinder (sounds to me like a typical Haflinger condition) you will appreciate the simplicity and ease of repair that the rubber bung system provides. It doesn't need to be fancy, it just works

Cheers,
Steve

Steve - thanks for that; I'm relaxed with the design but just wished I could get it to work . It did seal fine, so I am sure I will get it to do so again. As you say, it is a tight fit and it is not easy to know just how much force is needed to get the grommet to seat properly. The under surface of the top of the grommet has a curved face and it might have been nicer if this was flat so that one knew that it had been fully inserted. Anyhow, I will persevere as I am so nearly done!.

I _think_ that I have resolved the leak, but not sure which of the following was the more important. Firstly I obtained a washer with an oval hole in it from Dale, and understand that this is supposed to reduced the flow up towards the grommet. Not convinced that this does much, but it might. What I also did was to not push the grommet down in to the master cylinder too far; it is difficult to explain in words, but there is a small ridge 2/3rds of the way down the hole in the m/c, and I think that I may have pushed a ridge on the grommet down past this ridge; by only seating the grommet "half way" in it does seem to have stopped the weeping.

Fingers crossed!

Hi all,

I am having a similar problem with my brake master, not weeping but pouring fluid out from between the master cyclinder and the rubber grommet! I bought the replacement non-original master cylinder from Haflinger Technik and the rubber grommet as my Haflinger came without a master cylinder at all; but after reading this thread I realise that I need the slotted/oval washer. Unfortunately Haflinger Technik don't seem to have them in stock. Does anyone have a picture of what this should look like and the dimensions? Do you think it would be possible to fabricate? Or perhaps someone knows where I could source one?

Cheers,

OK guys, sorry but I cringe at some of this thread and would hate to see some one go through contaminated fluid in the system
Brake fluid eats all sealants over time, this is why sealant is never used on any brake system (auto shop 101).
Proper assembly is essential to prevent leaks.
The VW bung is exact match to factory part, and should be lubed with brake fluid or brake assembly lube then inserted in clean bore, pipe angle should not stress or pull the rubber(slotted washer is optional). It can take a little finessing to get the pipe to sit neutral.
Millions of VW's used this seal this way with no issues, but bad quality rubber can also cause issues.

FWIW, I have found the best VW cross over master cylinder is the early(till 57) type as they are 19mm piston and same over all length, the later ones are 17mm piston (and slightly longer) and result in higher brake pedal effort(you will also have to drill out mounting threads and plug 2 ports on either VW master). Plus side is they are inexpensive and readily available in a pinch