Front Master Cylinder Leaking

[Solidrick]

The master cylinder is leaking and has already damaged the paint on the tupperware. I bought it with the paint damaged , but it was because of a spill while topping off.

 

I removed the rubber boot and found a dried fluid sediment underneath. I cleaned it out, I did not see any rust.

 

Reassembled, adjusted the brake lever and it appeared to stop.

 

This morning I topped off the reservoir, and it immediately started leaking.

 

Do I need to rebuild this master cylinder or replace it?

 

By the way, I bought the bike last weekend and drove it from Philadelphia to Miami. I did an Iron Butt run saturday.

 

Rick

[lazywizard]

I bought the rebuild kit and changed it on the bike. Don't lose the little screws. The system bled out OK tho' not much air entered the system. About 2 hours and 3 beers.

[Ken H.]

Where is it leaking from? Around the top cap, or at the piston itself?

[Isatis_4CH92]

Hello,

 

General wisdom of this forum will tell you to change the master cylinder: mucho $$$

 

Some thrifty persons (ahem like me ) prefer to try first the repair kit: just a new piston+seal and the belows.

 

Theoretically the cylinder should leak again somewhere between 6 months and 2 years from the date of change.

 

Cylinders with date before 368 (36th week of 1998) are not anodized and should be the ones which develop the leak. The post 368 should do just fine.

 

Here is the tutorial of the genius Anton Largiadèr

 

http://www.largiader.com/tech/r11mc/

 

and here is mine on my K1 (everything is in french, yeah I know but you have at least pictures)

 

http://isatis.4ch92.free.fr/K1/kit_rep_Mait-Cyl_AV/reparation_M-C.html

 

Ride safe,

[tomk99r11]

Not enough specifics in your post to know where the leak occurs, but I encourage you to not ignore Ken's ? The caps can wick brake fluid upward from the reservoir IF the mating surfaces of the cap and the reservoir are not thoroughly dry and the reservoir is not over filled. The damn stuff keeps right on wicking and wicking and ...until the surfaces are clean. Maybe your leak is obvious, but check it out. Can save $ and time for riding.

[wolcott]

Not enough specifics in your post to know where the leak occurs, but I encourage you to not ignore Ken's ? The caps can wick brake fluid upward from the reservoir IF the mating surfaces of the cap and the reservoir are not thoroughly dry and the reservoir is not over filled. The damn stuff keeps right on wicking and wicking and ...until the surfaces are clean. Maybe your leak is obvious, but check it out. Can save $ and time for riding.

TomK99R11; I had a leak underneath my front master cylinder on my '99 RT. I got a new one from Chicago BMW for about $194 with the 2 copper crush washers and about $8 shipping. The labor from BMW shop to install was $157.30 without a brake bleed as the service dept. underestimated the hours because of the heated grips.I bled the fronts myself as it was an honest mistake on their part and told them i would bleed front brakes for the $157 price. I am including this info for the original poster to give him an idea on total costs. Labor should have been somewhat higher. Now, slight hijack: You say that the caps can wick fluid upward from the reservoir IF the mating surfaces of the cap and the reservoir are not throrougly dry. 1) Sometimes I notice what looks like some slight weeping around the phillips screws on the master cylinder top cap. I am sure that the fluid is not overfull and that the screws are not overtightened. Is this what you are talking about when you are talking about "wicking and not thoroughly dry surfaces?". Also, do you mean when the reservoir is "overfilled" vs. " not overfilled". Any advice appreciated.

[tomk99r11]

OUCH!!!! Big bucks. I have nothing to say that will make you think you did not need to spend the $. You note the weeping I describe. I was very careful to not overfill the reservoir, to make sure the dohickey on the underside of the cap was compressed so as to not extend down into the reservoir, had the mating surfaces dry as a pop corn fart, carfully filled the reservoir, installed the cap and the damn thing wicked! Peeled some of the paint around the screws and the cap. I have no magic instructions to avoid this eyesore. I try to be careful in everything I do but this was not good. So, I have learned to live with the peeling paint, and I look at other bikes every chance I get, but not many have my mess. Surely, not everyone has this service done by a dealer, nor are all of us neat freaks. Somewhere there must be a reservoir capacity for brake fluid, which would be good plus or minus a tad, since the system won't be totally empty. Best I can do Wolcott. Good luck.

[Vincent]

Just an FYI, the rebuild part number is: 32-72-2-332-037

[Ken H.]

Well the OP hasn't popped back in here with anymore info on the specifics of his leak.

 

I will say though, many people over-fill their reservoirs. Full is the middle of the sight window with the handlar turned so the reservoir is level. And the window is 2/3 of the way down the side of the reservoir to boot. So it not much is needed for it to be at the correct level.

[Rideoften]

I tried the cheap way first (rebuild Kit), lasted about 6 months on my 95 RSL. Then I did it the right way, new MC. I think it was about $170 a couple of years ago. BTW, neither comes with the very important rubber dust boot to keep trash and moisture out of the piston area. Not that hard of a job if you have a shop manual and clean work area. Make sure to get new copper seal washers for the hose. Never have experienced the cover leaking.

 

Ride Safe

Rideoften

[Fajah]

Did the rebuild kit 2 years ago, still holding. After the rebuild I compressed the front clalipers and backed fluid into the reseviour, did not spend time bleeding.