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Rotted master cylinder boot

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Rotted master cylinder boot

Posted by Colin Peterson at August 06. 2017

Touch wood, the only thing on my to-do list now is to replace the rotted boot around the end of the piston in the master cylinder for the front brake. It protects the cylinder from the elements, but it's an open door to them at present. Given that it's held in by a circlip – a sort of overgrown star washer with fewer teeth – that's designed not to come out without a fight, and given that the piston will pop out at the earliest opportunity – any tips on how to do this without the piston liberating itself and me making a hash of it? Or must I expect to take the whole thing apart? TIA

Re: Rotted master cylinder boot

Posted by david_evans at August 06. 2017

It might be considered a bit gash but you could just fill the area with silicon grease.

Re: Rotted master cylinder boot

Posted by Colin Peterson at August 06. 2017

True dat. Now that you've got me thinking sideways, maybe I could just pick out the old rubber and push a new boot and circlip over the top of the old circlip, IIRC there'd be plenty of room for that. And it'd be easier to keep the piston in place doing only that. Although it would leave much harder work for doing it properly next time. Cheers.

Re: Rotted master cylinder boot

Posted by Andrew Heathwood at August 06. 2017

Hello Colin

What you suggest doing would probably work okay.

I just wondered why not recondition the whole master cylinder whilst you're at it. The seal and boot kit is cheap enough. I found this job very straightforward and I'm no ace mechanic. If the boot is rotten might not the seals be as well?

In sorting mine, I used a suitable sized socket to drift the circlip into place.  I also found a deep crack in the hydraulic hose which was hidden by the switch cover. So I certainly found it worthwhile doing the whole job.

For peace of mind I'd at least check the hose under the switch cover.

Andy

Re: Rotted master cylinder boot

Posted by Colin Peterson at August 06. 2017

Previously Andrew Heathwood wrote:

Hello Colin

What you suggest doing would probably work okay.

I just wondered why not recondition the whole master cylinder whilst you're at it. The seal and boot kit is cheap enough. I found this job very straightforward and I'm no ace mechanic. If the boot is rotten might not the seals be as well?

In sorting mine, I used a suitable sized socket to drift the circlip into place.  I also found a deep crack in the hydraulic hose which was hidden by the switch cover. So I certainly found it worthwhile doing the whole job.

For peace of mind I'd at least check the hose under the switch cover.

Andy

Indeed! I've wondered about the life span of the seals, and I've re-fitted one of these master cylinders before, a long time ago. It's just that the brake's working fine, with fresh fluid – those of course could become famous last words, maybe I'm just being a bit impatient after losing July to a gearbox rebuild, followed by hassles with N*rvil downpipes. But I'd expect the seals to last longer than the boot, since the latter is left dry and exposed. Plus I have a Goodridge braided hose, no idea what their longevity's like, but the braiding means there's no way I'd see any cracks. Any ideas? I should probably ask them!

The master cylinder's been sleeved down BTW, I can't remember by whom but I note that Andover Norton sells these with reduced diameters now, I suppose they sell the 13mm seal kit too. Ok thanks Andrew, I'll ponder a little longer ...! BTW, if you used a socket to drift the circlip home, how did you keep the piston from popping out while you did it? Or am I imagining that that's a problem? Cheers.

Re: Rotted master cylinder boot

Posted by Andrew Heathwood at August 07. 2017

Colin

The master cylinder has obviously had some attention and if all works okay with no leaks then fine. Braided hose should be sound.

Concerning fitting the piston etc - from memory (not always reliable), I think I just compressed the piston, spring, boot and circlip on my workbench by hand enough to tap the socket once with a rubber mallet to get initial engagement of the circlip. I then tapped the circlip squarely fully home.

Hope you're on the road soon.

Andy

Re: Rotted master cylinder boot

Posted by Colin Peterson at August 07. 2017

Previously Andrew Heathwood wrote:

Colin

The master cylinder has obviously had some attention and if all works okay with no leaks then fine. Braided hose should be sound.

Concerning fitting the piston etc - from memory (not always reliable), I think I just compressed the piston, spring, boot and circlip on my workbench by hand enough to tap the socket once with a rubber mallet to get initial engagement of the circlip. I then tapped the circlip squarely fully home.

Hope you're on the road soon.

Andy

Great, I can imagine how that might be done, thanks Andy!

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