Front brake master cylinder rebuild

C

ChrisH

New member
Any ideas for this one please - All relating to a 1979 Mk 1 Monty - I rebuilt the rear master brake cylinder and calliper, all worked fine. Followed the same procedure (as per Lother et al) for the front master cylinder and nothing.

New hoses, rebuilt callipers, but when I fill the master cylinder reservoir with DOT 4  :) it doesn't go down when you squeeze the lever. I've got a one way bleed valve on the loose calliper nipple, If I disconnect the hose and put a finger over the end, there's air pressure when you squeeze the lever - but at the end of the day, the most I get is one very small bubble in the reservoir when I squeeze the lever - bleeding the front brakes is going to take until Christmas - any ideas?
 
Hi Chris,

  The one man bleeder valves are no good for an empty system, quickest way is with a Mityvac if you don't have one of them the next best way is to tilt the master cylinder so the return hole is the highest part of the system, dead easy with Jota bars just undo the bar end and tilt it up a bit, fill with fluid and tease the lever, you will find the system faily quickly gravity fills and air being air all comes out the top at the fluid return hole, as you work the air out give the lines a tap along their length and keep gently pumping the lever untill no more bubbles come out the top and you have a firm brake. This method is also dead handy if one or more of you bleed nipples are sheared off. Not a bad idea when the system is bled and their are no more bubbles comming up to push the pistons back into the calipers one side at a time this will dislodge any stubborn bubbles.


    Keith.
 
hi
just check the adjusting grubscrew in the lever is backed right out.my mate had real problems on his jota rear bleeding.i put a mityvac on it and it still would not bleed,he said its always been a right pig.when i looked closely the adjuster was ever so slightly out,so i backed it out allowing the piston to return just that little bit more,an hey presto it bled instantly.had the same on the sfc100 hydraulic clutch,backed it out half millimetre and it sucked the fluid straight in and bled.
Neale
 
Hi both

Thanks for the replies, I'm pretty sure that the grub screw is not stopping the return of the piston, there's play at the end of the lever but I'll double check tomorrow.

I don't have a vac device so I'll try taking the cylinder off the handlebars and tilting it the other way. As an aside, how do you know which hole at the bottom of the reservoir is the return hole??
 
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