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Master Cylinder Refurbishment


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I've managed to rescue my master cylinders which weren't in fact so much seized as just encased in years of crud (red rubber grease). I'm now proposing to refurbish them as there's no obvious signs of damage to the bores - in fact the brake m/c is spotless while the clutch m/c has some residual coating which, I'm pretty certain, I can easily remove - or the other components. It's 50 years plus since I last did a refurb and I can't remember for the life of me if I should grease all of the piston assembly (piston, spring, rubbers etc.) or just the piston. Can someone advise me please as to what's best practice these days and should I use grease at all or just use brake fluid to lubricate? Also, once I've refurbed them it'll be some months before I reinstall them so would I be better delaying the refurb until until I'm ready to install?

many thanks,


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you need to lubricate the piston back end ,pushrod end .

and the seals just dip in brake fluid

you can use a  red rubber grease or a white grease   if you can find it, but  whatever you use wont upset the seal,   the replacement wont last 50 yrs 

you may be luck and the kit has a sachet of appropriate grease but its unlikely these days .. they like to  leave you guessing


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Indeed, normal grease, copper grease etc are a no-no, I always use red rubber grease. In fact I bought a pot of it. Rarely used, but never goes off and always there when I do need it.

I have used very fine wet and dry to resurface the bores (800grit) along with a good squirt of WD40. I used a bit of wooden dowl with a slot in it, popped a few inches of paper in the slot, and the dowl in a drill. 

A good clean up with aerosol brake cleaner and assemble up. Brake fluid on the seal, then red grease on everything else. I would leave that until the time you want to fit them, safer that way.

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