hey guys ,

just recently i was able to remove the pesky screws to the reseviour of my hand brake and refill it . in the process bled the brakes with new fluid .

about a day later i noticed a drop of brake fluid on my side pocket lid ......oh "what the" ..anyhow i discounted it to the seal at the bottom of the container weeping after the release and now retensioning.

today, some weeks later there is more drips occuring in the same place .....a closer visual inspection reveals that its probably the rear seal to the master piston ...i can see oil all around the pivot and it seems to be eminating from the piston rod


after a ring around, best i can find is the bmw part locally for $146.00 (refurbish kit)

but here is the question ......

am ii likely to find the inside bores or the cylinder corroded ? and then up for the more expensive option of replacing the whole cylinder as well in a few months ....or am i likely to find that the new piston and seals will be good . ?

i imagine that the corroded rod has pushed through the rear seal ...further than normal durring the bleeding event , and hence slightly ripped the rear seal ......brake activation is good with no loss noticeable at all .



thoughts guys ?

I would have removed the piston and inspected the bore to be shure I got the correct answer, and then ordered.

Inge K.

havent ordered yet inge .....i can get the same kit landed here from motobins for about $50.00 aussie .

just wondering anybody elses experience with the same issue



will be pulling it out ....as we have a local holiday here today

Happened mine a couple of years ago, both front and rear. I opened them up and didn't like what I saw in there, so I replaced both cylinders with new ones from Motorworks. I figured it would be cheaper in the long run, not to mention safer.

8 months ago front one leaked. The bore was corroded. Got a second hand mastercylinder and put a new kit in and all is ok.
If you see corrosion, it'll leak.

Tried a refurbished one from old mate here at BM Shop. The bore was resleeved but the "hole" that the master cylinder sat in was corroded! A new seal didn't work.

I think there is a mastercylinder on Fleabay right now...and of course you can get it new from the 'bins.

I have had 3 done with a stainless sleeve and all are good but I have since found that a new one from Motobins was the same price.

If you decide to resleeve don't get Master cylinder exchange service at Wynnum to do it. I had one done there for the Ford and it was a very rough job and he wasn't prepared to rectify or refund he just reckoned I was a nit picking idiot and I had to call in the fair trading mob to sort him out and ended up getting a new one.

Mine has had leaks at both front and rear, and replacing only the piston (original from maxbmw) has worked fine, but cilinders were checked before deciding.
Best regards
JAP

Mine leaks too, but from the reservoir.
It seems like the rubber under the cap doesn't seal around the screws properly, and liquid gets out that way (and humidity in).
Any fixes?

You can buy just the rubber bellows which includes the cap seal http://www.motobins.co.uk/bmw-parts.php?model=K Series You will need to copy and paste this link.

sitting duck ....check the o ring under the resevoir ....



some news ....well at least ....i flushed out the piston/lever end from outside the cylinder with degreaser till i could ge some squishing eminating from the master cylinder / seal at the back where the rod pokes out of the body .....then went for a ride up and down nebo (nebo is a 31k long windey mountain road one way ......and used the front brake lots) ......so far no oil contamination present anywhere ....but i know itll be back soonish



i will get some funds together and put an order in to the bins in the not too distant future .....thanks for the shared experiences guys ...mucho appreciated

Charlie, you can have mine when the 20mm arrives. It's a known working master cylinder.