The New And Improved Unofficial R65 Forum V2

Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: AlfromNH on October 06, 2013, 03:48:41 PM

Title: 13mm Master Cylinder disassembly
Post by: AlfromNH on October 06, 2013, 03:48:41 PM

I'm trying to figure out if this master cylinder is salvageable. I have it off the lever assembly, but I want to take it apart to be able to clean it thoroughly. Does the reservoir come off? I can't find any fasteners, maybe it's pressed in?
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fi1350.photobucket.com%2Falbums%2Fp763%2Facarey3%2FIMG_20130930_074928_758_zps6c597b3f.jpg&hash=e023e2d6cdbb135be83fcf476a0d98353503675a) (http://s1350.photobucket.com/user/acarey3/media/IMG_20130930_074928_758_zps6c597b3f.jpg.html)

Title: Re: 13mm Master Cylinder disassembly
Post by: Bob_Roller on October 06, 2013, 03:59:59 PM

You can remove the piston / seal from the master cylinder , but the reservoir is not meant to be removed, it's bonded to the metal part of the master cylinder .

Havn't heard of any sucess of reattaching it, if it does come off or becomes loose and leaking .

Title: Re: 13mm Master Cylinder disassembly
Post by: nhmaf on October 06, 2013, 04:39:50 PM

This is why a number of folks upgrade to the rectangular version - because it is intended/designed to be able to replace the removable reservoir which has a replaceable o-ring on its outlet.   But, I do know of some ambitious souls who managed to carefully pull theirs apart and epoxy it back together again - but not something I personally would put too much confidence in.

If the piston & seals are replaced and the bore looks good, you may be OK, unless it exhibits leaking from around the base of the plastic reservoir - that is usual the point of no return for these round m/c models.

Title: Re: 13mm Master Cylinder disassembly
Post by: AlfromNH on October 06, 2013, 08:19:08 PM

Thanks guys. I don't think I'll try to get the bowl off. i guess I'll clean everything up, hone the cylinder and then assess things. I don't want to buy a new piston and then find out the something else is unusable.

Title: Re: 13mm Master Cylinder disassembly
Post by: Luca on October 07, 2013, 01:54:36 PM

If you have trouble finding a hone, look for one advertised for caliper pots (brake hone).  That's what I did when I redressed my MC bore.

Some folks will say to never clean the MC with water... but I did and it worked just fine.  Just make sure to finish up with compressed air or a hair dryer.  I'd be wary of solvents around the plastic bits.

There is a very tiny return hole in the bottom of the master cylinder that will easily clog.  If it does clog, the brakes will drag/seize. Best to gently poke through with a strand of fine wire before reassembly