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Clutch cylinder

Technical issues not related to a DLOC car marque, eg tyres, ethanol, other car makes, etc. and legal, political and insurance
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New Dexter
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Clutch cylinder

Post by New Dexter »

Good evening Gentlemen

This afternoon I fitted a new clutch master cylinder to my vehicle. It had been leaking for some time but I managed to remove it, clean up the mess and replace with a complete new cylinder rather than re-seal the old one.
I put it all back together and using a self-bleeding vacuum pump I thought it would be easy. However, all I had was a complete lack of pedal pressure.
I thought I would try the old fashioned method of pumping the pedal several times to try and build up some pressure, jamming a piece of wood between the seat and pedal once some semblance of pressure was achieved. Nothing.
Then I noticed that the fluid in the reservoir was very frothy. Allowing it to settle I was able to pump the pedal and view the fluid and noticed a column of bubbles arising from the bottom of the reservoir to match each pump of the pedal.
My impression is that this brand new cylinder, purchased from a motor factor last week is U/S. Would I be correct or have I missed something?

Stan Thomas
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Location: Penkridge. Staffs.

Re: Clutch cylinder

Post by Stan Thomas »

Check the slave cylinder has the input pipe at the bottom, and the bleed nipple at the top - otherwise you will never expel all the air in the sytem.

Pump the pedal slowly and deliberately (don't just kick at it frantically like you do the mother-in-law) with a short pause at the end of each stroke for the master cylinder to recuperate. You could also get an assistant to close the slave cylinder bleed nipple at the end of each down stroke of the pedal, and release it after the pedal has returned - then complete the cycle again until all air is expelled.

New Dexter
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Re: Clutch cylinder

Post by New Dexter »

Stan,

Thank you for your reply and the warning that the inlet pipe must be at the bottom. Fortunately it is but by the slave cylinder's design this puts the bleed nipple so close to the chassis that it's almost impossible to fit a spanner and move the nipple more than 1/8 turn. An open-ended spanner is useless it has to be a ring spanner
Unfortunately I do not have any assistance here. That's why I bought one of those vacuum bleeders last year but when this is fitted to the bleed nipple it's impossible to lift the ring spanner off the nipple and rotate it.
I have, somewhere, a bleed tube which has a valve fitted and I will see if that works. However, while depressing the pedal slowly several times to try and generate some pressure in the system all I end up with is a reservoir full of frothy fluid.

Stan Thomas
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Re: Clutch cylinder

Post by Stan Thomas »

You can of course remove the slave cylinder to bleed it if it is easier to get at, because when you replace it onto the push rod it will merely displace the fluid back to the reservoir.

That said, are you sure it is not the slave cylinder that is faulty and possibly drawing in air - as this is usually the more common component to go awol.

New Dexter
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Re: Clutch cylinder

Post by New Dexter »

I remembered that I have a Gunson's Ezibleed which I have used with varying degrees of success and once I had changed the cap for a smaller one screwed it on to the cylinder, applied about 7psi and promptly created a small fountain of fluid down the cylinder wall. Even using another cap did not work and it must be the sealing washer inside the cap as I had the same air leak on the original master cylinder.
I shall follow Stan's excellent advice and remove the slave cylinder for better access to the bleed nipple. More later, probably.....

New Dexter
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Re: Clutch cylinder

Post by New Dexter »

I tried removing the slave cylinder following the excellent advice but then forgot to secure the cylinder piston so that a quick pump on the pedal caused the piston to come out. 0/10 for common sense then. However, this enabled me to inspect the slave cylinder bore and given that it looks like the slave cylinder has been on the vehicle for some centuries I decided to buy a new one. All of £8.50. (Outrageous :lol:)
Bolt it into place, after cleaning the UNC threads and even though one of the bolts is hidden from sight. Pump the pedal, gently, secure in the down position with a convenient length of 2 x 2 jammed against the seat. Open the bleed valve a touch and..... I have pedal pressure and managed to remove the vehicle from the barn without performing a kangaroo performance across the yard.
It remains to be seen if all is well later this evening or even tomorrow.
As one "senior" member of the DLOC said one evening, it's always nice to do a bit of fettling and achieve a satisfactory result.

New Dexter
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Joined: Fri Feb 12, 2016 9:41 am

Re: Clutch cylinder

Post by New Dexter »

Predictive text has its advantages and it can correct my bad typing but when I mis-type performing and without my checking it gives me perfuming I suspect that one or two reader of this post might have raised an eyebrow, or perhaps both....

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