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Slave Cylinder Leaking From Bleed Valve


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#1 minicooperr

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Posted 14 January 2020 - 03:59 PM

Been having issues with my clutch for ages been trying everything I have now swapped the slave and the lines to a complete one piece braided line and I’ve been trying to bleed it with one of the vacuum pumps and when I close the nipple I continue to get bubbles and fluid through the system? What do I do

#2 cal844

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Posted 14 January 2020 - 04:38 PM

Do away with the vacuum bleeder, get an assistant to pump the pedal, make sure the pedal is held down before you close the nipple

#3 g0myw

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Posted 14 January 2020 - 05:11 PM

OK minicooper, I use the vacuum method on my bikes.
You do get that 'sucking - in' of air through the bleed nipple thread.

In my experiance [on many bikes] it does not affect the  overall bleeding process.

Yes its very disconcerting.

But the vacuum is pulling through the fluid - so the air in your system is getting drawn out.

 

Having said all this - for the Mini , I'm now a convert of the Gunson .!



#4 Chris1275gt

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Posted 14 January 2020 - 06:20 PM

If all else fails unbolt the slave from the housing remove spring pull it off the push rod, hold it vertically with the nipple at the top get someone to pump the pedal bleed it and put it back together. It works 100% every time.

#5 minicooperr

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Posted 16 January 2020 - 07:45 PM

If all else fails unbolt the slave from the housing remove spring pull it off the push rod, hold it vertically with the nipple at the top get someone to pump the pedal bleed it and put it back together. It works 100% every time.

 

 

Thanks for the advice but would this not push the seal out and cause fluid to go everywhere?



#6 Chris1275gt

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Posted 16 January 2020 - 08:13 PM

If all else fails unbolt the slave from the housing remove spring pull it off the push rod, hold it vertically with the nipple at the top get someone to pump the pedal bleed it and put it back together. It works 100% every time.

 
 
Thanks for the advice but would this not push the seal out and cause fluid to go everywhere?

No, as you will only press the pedal when the nipple is open so there will be no pressure on the piston so it won't move

#7 Moke Spider

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Posted 17 January 2020 - 07:23 AM

Been having issues with my clutch for ages been trying everything I have now swapped the slave and the lines to a complete one piece braided line and I’ve been trying to bleed it with one of the vacuum pumps and when I close the nipple I continue to get bubbles and fluid through the system? What do I do

 

This is one of the problems with Vacuum Bleeders. Although the Nipple is closed and no fluid will come through it, the hole on the side of the nipple, that's down in the thread of the Cylinder is open to atmosphere through the threads of the Nipple. Only a small space, but not sealed !

 

The other issue with them is the Hydraulic System is designed to work under pressure not vacuum. Not the issue you appear to be having here, but if you look at the design and shape of the seals, you'll see that they work well under pressure - more pressure, the tighter they seal against the cylinder and piston to which they are fitted.

 

However, under Vacuum, the Lips of the Seal will pull away from the Cylinder Wall, loosing any seal it had and allowing Air in to the system, so you soon end up chasing your tail. While it's usually the cylinder closest to where the Vacuum Bleeder is fitted that does this, Air can be drawn in from other Cylinders, including the Master Cylinder.



#8 super6al

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Posted 17 January 2020 - 01:35 PM

Doh! wish this had been posted last week - I've just bought a bugger  >_<



#9 Moke Spider

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Posted 17 January 2020 - 07:30 PM

Doh! wish this had been posted last week - I've just bought a bugger  >_<

 

Oh,,,,, 40 lashings to me,,,,,
 

If it has a means of reducing 'flow' on the tube you fit up to the Nipple, if you tun it right down to a very low flow rate, you should be OK, but, if you find you don't seem to be getting rid of all the Air, then this is probably the likely cause.

 

They can be a good way to get fluid in to a dry system, then go over to the old school way with 2 people, one pumping the pedal and the other working the bleed nipple, with a clear hose off in to the old Coke Bottle.






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