The New And Improved Unofficial R65 Forum V2

Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Bill Conquest on September 14, 2009, 10:41:11 PM

Title: dLeaking brake cylinder
Post by: Bill Conquest on September 14, 2009, 10:41:11 PM

Hi All - Just found my front brake master cylinder is leaking & am wondering if there's a re-build kit available? It seems to be coming from where the m. cylinder bolts to the brake handle/switch assembly, havn't taken it apart yet but i'm wondering if it's new m. cylinder time... need to order parts quick! It's a '79 R65 with the round m. cylinder, are there gaskets or rubber parts that could be worn out? Thanks in advance..
Bill Conquest

Title: Re: dLeaking brake cylinder
Post by: Bob_Roller on September 14, 2009, 10:48:57 PM

You can get the parts from BMW, I just looked at what the prices were for a replacement 'piston' assembly for my '84 LS, and looks like around $60, for the rectangular reservoir master cylinder .

I was asking around our ground vehicle maintenance shop here at work, and I was told that NAPA, and Car Quest have 'cup' seal replacements available, so you may not need to replace the 'piston' assembly .

I would remove the master cylinder, and open it up, I wouldn't be too surprised if you find corrosion and pitting in the cylinder bore, due to your tropical/salt air environment there in 'paradise' .

Title: Re: dLeaking brake cylinder
Post by: Bill Conquest on September 16, 2009, 12:57:06 AM

Thanks Bob - Guess i'll take it apart & see.. yes, corrosion is one of the prices of living here!
Bill Conquest

Title: Re: dLeaking brake cylinder
Post by: Yikes on September 16, 2009, 07:52:34 AM

Be prepared, separating the master cylinder from the metal body is a royal PITA.  Takes a lot of not-at-all gentle persuasion.  I ended up having to crack mine apart with a hammer and a stiff scraper, but after all that the bore was OK and after a good cleaning and repaint a new piston assembly fixed it fine.  Oh yeah, had to repaint my fender that was ruined by the dripping brake fluid.

Title: Re: dLeaking brake cylinder
Post by: Bob_Roller on September 16, 2009, 11:42:47 AM

I did some checking around locally, for replacement seals for the master cylinder, and no one has seals that small in daimeter .

Title: Re: dLeaking brake cylinder
Post by: Lucky_Lou on September 16, 2009, 01:24:05 PM

I have a very slight leak on mine ?? started a thread somewhere about it same model at first i thought it was the seal between the reservoir and the casting now im not convinced its either the piston seal or the o ring where the two cast parts meet anyone know how to tell for sure.
Lou

Title: Re: dLeaking brake cylinder
Post by: Bill Conquest on September 17, 2009, 10:10:16 PM

Well, I ordered a re-build kit from Bob's... not cheap at 70 + dollars, plus a new cap and gasket. And i'll be doing some painting also from the dripping fluid. The cylinder didn't want to come off of the brake housing after unbolting but some gentle persuation with a rubber mallet worked. Can't tell for sure but it looks like the washers on the piston are a bit worn, we'll see!
Bill Conquest