Clutch Master Cylinder

[Smroot]

My clutch master cylinder is leaking. I'm going to replace it but I read that it the master cylinder has failed the slave isn't far behind. Should I replace this as well just to be safe?

Root

[kevtherev]

you could... but would you stop there
but my philosiphy is ..if it ain't broke, don't fix it

[ricicles]

replaced my clutch master last year without doing the slave, why bother if its ok?

[Smroot]

Thanks, sounds like good advice.
Root

[Nicola&Tony]

Before you change the master cylinder, have a look to see if the bleed nipple on the slave cylinder can still be opened and closed. If it looks rusty, give it a few good soakings with a penetrating oil first. When I tried to open it, it sheared off so I had to change both cylinders.

Tony

[davidvincent]

Hi

I replaced my knackered master cylinder a few months ago, it then took about 2 weeks for the slave to give in... some advice I got here was that the new master cylinder adds pressure to the system so in turn the slave is under more stress than it has been used to.... so, whilst I would usually say 'if it aint broke don't fix it' on this occasion I would suggest considering it.... mine was fine one day then dumped it's fluid (via the slave cylinder) over night which left me with big problems in getting where I had to go that day :

Just my thoughts... let us know how you get on.

Dave

[HarryMann]

'm going to replace it but I read that it the master cylinder has failed the slave isn't far behind.

Sounds a bit like old wive's tales, apart from of course the age of the slave is the same as the master usually...

and as for more pressure for a new master cylinder, not true, the pressure is determined by the clutch spring resistance... unless the pushrod is too long or slave positioned incorrectly.

It's what happens to the slave when its bled after a new master cylinder is fitted if anything that makes it go soon after is my guess...

The slave can be jammed to stop clutch movement when bleeding, helps express all the air as well as old fluid if it can't get pushed open...

[davidvincent]

'm going to replace it but I read that it the master cylinder has failed the slave isn't far behind.

Its what happens to the slave when its bled after a new master cylinder is fitted if anything that makes it go soon after is my guess...

I bled the system at the master cylinder when I fitted the new one - to avoid having to bleed the slave... it could have just been a coincidence i guess but I'm sure the fact that the master was leaking (knackered and needed replacing) would mean that the pressure from the master to the slave would be less than normal, and that would mean that by replacing the master and stopping that leak/escape that the pressure would be restored/increased and could cause an equally as old (and a lot more exposed) slave cylinder to pop it's seal.... maybe?

Dave

[HarryMann]

A few points there...

Its a good idea to bleed the whole system through as if a master has gone there's a good chance air in the system subsequently, plus also a good idea to refresh old fluid anyway.

If the clutch previously worked (obviously it did up till a short time before master went) then the pressure was enough to open it, which is all that's required of any hydraulics - only if the clutch is jammed, an up-rated clutch is fitted, if its overtravelling or the new master is a different (larger) bore (unlikely) will the pressure be any different to the day it was born!

If slaves do consistently go soon after a master change, then its probably due to increased travel of the slave, the seals then travelling over a part of the bore previously untouched for years. This'll be due to any old air being bled out, and the new master maybe then moving a fraction more fluid... but the pressures will stil be just what is needed to open the clutch, that's how hydraulics work - the pressure can't be any higher than the resistance at the other end..

[davidvincent]

If slaves do consistently go soon after a master change, then its probably due to increased travel of the slave, the seals then travelling over a part of the bore previously untouched for years. This'll be due to any old air being bled out, and the new master maybe then moving a fraction more fluid...

ok, i see....

[phade]

Hi everyone,

I replaced my clutch master cylinder nearly 3 years ago and the clutch slave cylinder is still ok with no leaks what so ever.

I agree with one of the above posts "if it ain't broke, don't fix it".

[BMEC]

Hi Dave
I am interested in your comment that you were able to bleed the system at the master cylinder without bleeding the slave. I had wondered myself if this would be possible by taking care when fitting the new master ( I too have sheared the screw on top of the slave )
I know you said your slave packed up soon afterwards but could you confirm that the 'master bleeding' worked OK.
Cheers Gordon

[davidvincent]

Hi Dave
I am interested in your comment that you were able to bleed the system at the master cylinder without bleeding the slave. I had wondered myself if this would be possible by taking care when fitting the new master ( I too have sheared the screw on top of the slave )
I know you said your slave packed up soon afterwards but could you confirm that the 'master bleeding' worked OK.
Cheers Gordon

Hi Gordon

Sorry, I relied to this ages ago but for some reason did not make it to the thread..?

anyway, yeah I managed to bleed it at the master cylinder by a) putting a sheet of cling film under the filler cap of the hydrolic fluid reservoir and then replacing the lid, this reduces the amount of fluid you actually lose.... b) before installing the new part, attempt (this is a messy job top to bottom so put rags down) to pour clean fluid into the new part..... c) once installed do not fully tighten the nut that secures the metal pipe (the pipe that travels towards the slave cylinder) - leave it a half a turn undone and whilst pumping the clutch pedal (or ask someone to help) you can use a spanner on the nut as you would a bleed nipple, expel all the air and one its just clean fluid passing through you tighten up the last turn of the nut.

I did this and it worked well, hope that helps.

dave

[BMEC]

Hi Dave,

Did the job of replacing the clutch master cylinder as you suggested (bleeding at the master cylinder only) and it worked fine. I did buy a new slave in case something went wrong but have not needed to use it. I suppose it is there if I need it but I bet it is a so-and-so to replace.

Thanks Gordon

[jpee]

Had master replaced a year ago slave still fine. Just read that back. should we still be using the terms master and slave?

Are there any other non PC terms relating to the mechanical function of our 'pandemic' vans (they can be found worldwide, and cause mental illness in owners)