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Leaking master cylinder
hobzy - 7/11/09 at 05:26 PM

Seems my brake master cylinder is leaking from where the shaft from the pedal enters the cylinder. Its a very slow leak, but after a few weeks in the garage, the footwell is well and truly soaked in fluid and i reckon ive lost half the reservior

So, upgrade or replace with another sierra one? Also a whats the easiest way to get the new one onto the old lines? Run a new line from the first opportunity or is there some way of just replacing the last few inches?

As I didnt build the car, every fix is a new learning opportunity!

02GF74 - 7/11/09 at 06:33 PM

what do you mean by upgrade? chose the master cylinderbore wisely.


first you need to take the master clinder out and take a peak - you shouldbe able to undo the pipe to it, bend them a little it get out of the wyay but not too ,much.

then take apart and clean the master.

if the bore is scored, it is scrap.

look t the seals, if there is anyt sign of dmaage, wear, tear etc then those are scrap too. it may be hard to see anay damage though.

then you have option of replacing innards - seal kit or fitting a replacement.

look at the prices for each and weigh up the possiblility that fitting a new seal kit may not fix the problem if there is damage to the master so you willgo through the whole rimarole of undoing the pipes again,. not that there si a limit number of time you can do that as you will bend the copper pipe as well as deform the ends each tim you nip up the nipples but you'll probably be ok.

also there are at least 2 different sierra master cylinders so do not throw yours away until the replacement is in your hand, or better still fitted.

if the master looks ok, then got for the seal kit. maybe block of the ports, fill with fluid and leave for a week to see if it leaks.

hobzy - 7/11/09 at 07:33 PM

Cheers 02 thats really helpful stuff.

by upgrade I suppose I mean go for a willwood MC or something, and as you say pick the right bore. Suggestions on that front would be good.

adithorp - 7/11/09 at 08:13 PM

Take it out first. It should be possible to just spring the pipes out without bending them. Strip it down and inspect.
Three choices then...

1. If the bore looks OK you could fit a seal kit. If you do, make sure you wet all the parts with brake fluid before you assemble. This helps prevent damage to the seals as they go in and makes it easier to bleed.

2. Fit a new cylinder.

3. Replace the cylinder with one with a smaller bore. That gives more brake presure but also more pedal travel. Early Fiesta non-servo master cylinder is the easiest with the same bolt pattern (and pipe lay-out?) and will give better brake feel.

adrian

theconrodkid - 8/11/09 at 09:44 AM

is it worth messing around on such a safety critical part?
http://www.brakeparts.co.uk/
get a new one,cheap enough from these peeps

britishtrident - 8/11/09 at 10:04 AM

quote:
Originally posted by hobzy
Cheers 02 thats really helpful stuff.

by upgrade I suppose I mean go for a willwood MC or something, and as you say pick the right bore. Suggestions on that front would be good.


Willwood MC is the last thing you want to use --- if you change the MC to reduce pedal pressure go for a smaller bore cylinder ie early Fiesta non servo or some of the Fiat cylinders.

Don't assume anything with Willwood name is an upgrade, Willwood tandem dual curcuit mastercylinders have larger bores than the Sierra this great increases how hard you have to push the pedal to stop the car.

The old UK Brands Lucas-Girling and Lockheed are the best designs of mastercylinders and they can be easily overhauled.

hobzy - 8/11/09 at 12:06 PM

Nice one. Ok then, fiesta it is. Any idea on the year that matches the closest to the bolt pattern etc?