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Leaking brake pipe at master cylinder connection


Andrew
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Suggestions and advice please.

Two years ago I replaced my brake master cylinder on my 13/60 Herald .  This unit was a new unit supplied from a reputable parts supplier.  All went well when all connected and all air bled from the system and no leaks.  Now after two years the union at the MS connection had stared to leak.  I have tried to nip up the mail connecter which cured the leak for about a week, now it is leaking again. Any wise words of wisdom please to cure this issue.

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its probably down to age and reused fittings,  the pipe sleeve nuts if over tightened  tend to split at the flare flange,  the pipe flare it possible crushed and may need a re flare

if that makes the pipe too short , use a decent brake hose to act as a repair section  screw hose into cyl. and connect bundy  this may sound a bodge but can be effective when stuck. 

or do it right  and replace a length  of bundy  with a new flared end and new nut

Pete

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I had similar situation on my Vitesse though a junction near the rear . It was a case of replacing the brake pipe section or trying a sealer. I used https://www.ebay.co.uk/itm/Draper-Brake-Pipe-Air-Line-Locking-Seal-Gas-Oil-Fluid-Airline-Sealant-Sealing/382286975993?epid=6017745510&hash=item59021453f9:g:x4MAAOSwhVxaDc2a and it worked 

Hope this helps 

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I had a similar problem. It takes very little additional pipe to cut off the old flare and re-flare but do remember to add the sleeve nut before the re-flare - I nearly forgot DOH! :wub:

Aidan 

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  • 3 weeks later...
On 6/1/2018 at 3:32 PM, Andrew said:

Now after two years the union at the MS connection had stared to leak.  I have tried to nip up the mail connecter which cured the leak for about a week, now it is leaking again. Any wise words of wisdom please to cure this issue.

Is it leaking around the screw thread, or from the centre ie around the pipe?

You may be able to improve the seal by reflaring the pipe, but it may be the case that the threads on your alloy master cylinder are too worn to tighten sufficiently to allow a good seal anymore; have a look at the threads and see if there's any wear or damage. You may be able to rethread them (to a certain degree)and a new nut may help, but if if the threads in the alloy are wrung or damaged it'll have to be a replacement.

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30 minutes ago, Colin Lindsay said:

Is it leaking around the screw thread, or from the centre ie around the pipe?

You may be able to improve the seal by reflaring the pipe, but it may be the case that the threads on your alloy master cylinder are too worn to tighten sufficiently to allow a good seal anymore; have a look at the threads and see if there's any wear or damage. You may be able to rethread them (to a certain degree)and a new nut may help, but if if the threads in the alloy are wrung or damaged it'll have to be a replacement.

This may be way off-mark but... the brake pipes seal on the flare against the taper at the bottom of the female thread. The thread itself is not exposed to fluid at all. Is there any reason it's not possible, therefore, to helicoil it?

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Sod's law.

bought a new master cylinder, new length of brake copper brake pipe and all the required fittings.  Just before I started I thought I would just give the leaking union another go as I do not want to disturb the brake hydraulic system.  So loosened of the union gave the pipe a wriggle so it entered the Master cylinder a bit of a different angle, tightened the union quite tight and would you believe it seems to have cured the leak.  Any thoughts out there 

regards

Andrew

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As john suggests this seems to be down to the shape and fit of the pipe flare onto the registered location in the base of the thread

The angles and compression of the pipe flare make the seal , and in reality the pipe is a use and fit once not do it up multiple times over the many years,    so wear and tear in these  type of connections is inevitable

Pete

 

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