Dreaded clutch master replacement ZT-T 190

[mgb66]

I hesitate to post my query about a clutch master cylinder replacement I've just done on a ZT-T 190, but am in desperate need of advice if available.
I'd noticed that changing gear would occasionally become difficult on journeys that required a lot of stop start, and on the premise that the clutch had been renewed four and a half years ago, I had suspicions about the master cylinder and had ordered a spare from DMGRS back in 2021.

The job of changing it looked a nightmare so I had undeniably put this off until last week, when the clutch pedal went down and stayed there. Unfortunately parked on the road but at least outside the house.

I've managed to fit the new MC to the old pipework on the kerb (won't replay that nightmare!) but so far have had no luck with bleeding the system.

I rigged up a plastic tube and small funnel into the MC reservoir on the basis that I wanted to clear out all the old fluid which looked quite contaminated.

A Vizibleed was attached to the bleed nipple from the slave cylinder and I pushed through an 120ml or so.
However at no point am I getting any pressure in the system, and I suspect fluid is tending to be pushed out of the reservoir as much as through the system.
The presumption is that the slave cylinder was changed with the clutch and I can't see any evidence of fluid leaking from the bell housing.
Can any one give me a clue or answer as to what might be going on?
Having bled a few systems over the years I'm a bit mystified as to what is happening.

[Mike Noc]

With the help of an assistant try bleeding it the old fashioned way. When you have done that then split the quick disconnect coupling and press the clutch pedal. If it is rock hard then the master cylinder is fine. Reconnect it to the slave cylinder and if the pedal goes to the floor and stays there then there is a problem with the slave cylinder.
The level in the master cylinder rises for the first bit of pedal travel - all quite normal so don't overfill it.

[Ducati750cc]

One other way to bleed it is to do it back to front.


A good fitting pipe on the bleed nipple, wedge the pedal fully up and using a syringe to flush fresh fluid through the slave to the reservoir, initially siphon as much fluid as possible out of the reservoir, again with a syringe and pipe and several times through the bleeding process, use a few old towels for spillage, continue till the fluid is clean.


I've found that this way has solved similar problems on clutch and brake systems

[Number 6]

Have you removed the rubber "Condom" from the master cylinder before you started??

[mgb66]

Many thanks for your suggestions. I gave myself a day off yesterday considering my options if the slave cylinder is at fault. If the clutch plates have been contaminated I fear that much as I like the car (and it's ULEZ compliant...) that might be the end of the car.
I will continue trying to isolate the problem and follow up with the results, and yes, I did remove the insert in the new master cylinder which I noted had been removed from the MC I replaced.

[Costa Fortuna]

Originally Posted by Ducati750cc

One other way to bleed it is to do it back to front.


A good fitting pipe on the bleed nipple, wedge the pedal fully up and using a syringe to flush fresh fluid through the slave to the reservoir, initially siphon as much fluid as possible out of the reservoir, again with a syringe and pipe and several times through the bleeding process, use a few old towels for spillage, continue till the fluid is clean.


I've found that this way has solved similar problems on clutch and brake systems

This is the best way - it pushes the air up in it's normal direction.

[mgb66]

Having tried to consider all the suggestions from the Forum for bleeding the system after fitting the replacement Master Cylinder, and not enjoying the mess I was getting into in the confined space underneath the dashboard I looked at the various options. Traditional - pedal/bleed, vacuum and pressure. Given I wanted to get rid of any old, contaminated fluid as far as possible, and how difficult it was to keep topping up the reservoir with its 50cc capacity I opted for a Gunson Eezibleed.
After all the headache of the past weeks efforts this proved to be very straight forward. Using a skinny spare at 10psi as the pressure vessel I bled the system until the fluid ran clear without air bubbles. I then re-pressurised the tyre and did it again a couple of times until I had run through at least 200cc. Each time the pedal was firm.
After disconnecting the Eezibleed I used a syringe to reduce the fluid in the MC reservoir to approximately half way and put the rubber insert back in prior to tightening the cap up.
My worry that the Slave Cylinder might have failed seems not to be the case, thank goodness.
It is hard to believe that sorting clutch hydraulic issues on these cars should take up so much of everyone's time and effort due simply to positioning of the Master Cylinder, but better not start me off and there's been enough said about that already!
Thanks to everyone for the practical and moral support.

[drewbie]

Originally Posted by mgb66

Having tried to consider all the suggestions from the Forum for bleeding the system after fitting the replacement Master Cylinder, and not enjoying the mess I was getting into in the confined space underneath the dashboard I looked at the various options. Traditional - pedal/bleed, vacuum and pressure. Given I wanted to get rid of any old, contaminated fluid as far as possible, and how difficult it was to keep topping up the reservoir with its 50cc capacity I opted for a Gunson Eezibleed.
After all the headache of the past weeks efforts this proved to be very straight forward. Using a skinny spare at 10psi as the pressure vessel I bled the system until the fluid ran clear without air bubbles. I then re-pressurised the tyre and did it again a couple of times until I had run through at least 200cc. Each time the pedal was firm.
After disconnecting the Eezibleed I used a syringe to reduce the fluid in the MC reservoir to approximately half way and put the rubber insert back in prior to tightening the cap up.
My worry that the Slave Cylinder might have failed seems not to be the case, thank goodness.
It is hard to believe that sorting clutch hydraulic issues on these cars should take up so much of everyone's time and effort due simply to positioning of the Master Cylinder, but better not start me off and there's been enough said about that already!
Thanks to everyone for the practical and moral support.

Eezibleed everytime for me. Had to source an old MC cap because there wasnt one that fitted in the kit at the time. Prior to bleeding I use a leak test pressure of 20psi then bleed at 15psi. I've never refitted the black condom, i fill the reservoir to 10mm from the top and just found a neat fitting O ring for the cap, job done.