Odd (Intermittent) Hydraulic Problem

Sounds like the clutch slave cylinder needs replacing.

Could be either master cylinder or slave cylinder problem. If there is no leak at the slave then it is almost certainly the master cylinder. Before replacing it flush the system through with fresh fluid as there may be only a bit of crud stuck somewhere.

mrcheerful

Master cylinder, not slave.

He's getting the same symptoms I got when my slave cylinder failed, although I kept driving it until it went to the floor and wouldn't come back up again.

If the slave had failed, the fluid would be leaking out.

: When you press it your : foot just sinks to the floor with almost no resistance and the clutch : doesn't disengage at all. If you lift your foot again however it : usually is working the next time. The reservoir is full, the fluid is : newish and there is no sign of corrosion or bits separating from each : other.

The one-way valve between the reservoir and the master cylinder is occasionally sticking open.

Ian

The what??????????

: > The one-way valve between the reservoir and the master cylinder is : > occasionally sticking open. : >

: The what??????????

On a coupleof may cars there is a valve between the reservoir and the clutch master cylinder. This is so that after the clutch cover plate has pushed the slave cylinder piston back, fluid from the reservoir makes up the rest of the master cylinder piston travel: it's how the self adjusting works. If this valve sticks open, perhaps because of a piece of dirt, the master cylinder piston simply pushes fluid back into the reservoir when the pedal is pressed. In my experience it's a good way of getting an odd intermittent clutch failure.

Ian

On all the master cylinders I have worked on, the self adjusting works by having a transfer port from the reservoir to the cylinder which is open whenever the cylinder is at rest, but as soon as you press the pedal the seal on the piston covers the port, and pressurises the system. If it was done using a one way valve, it would not work as there would be nowhere for the fluid to go when it expands due to engine heat etc.

: > On a coupleof may cars there is a valve between the reservoir and the : > clutch master cylinder. This is so that after the clutch cover plate : > has pushed the slave cylinder piston back, fluid from the reservoir : > makes up the rest of the master cylinder piston travel: it's how the : > self adjusting works.

: On all the master cylinders I have worked on, the self adjusting works by : having a transfer port from the reservoir to the cylinder which is open : whenever the cylinder is at rest, but as soon as you press the pedal the : seal on the piston covers the port, and pressurises the system.

Maybe it's changed then. I can send you a spare one-way reservoir valve for a Girling 5/8" master cylinder if you want!

Ian

I think they do normally have a one-way valve, but on the ones I've seen, it's been built into the piston assembly rather than a separate item.

Cheers,

Colin.

No taa, don't strip en these days, just chuck a new one on

Sounds the most likely to me. Many thanks for all who replied.

On a further note does anyone know a likely supplier of an overhaul kit. Hyundai only sell a new cylinder and want £150 for it which is probably more than the entire car is worth and ADL only sell the slave.

Alternatively do the piston rubber seals come in standard sizes which I could match up in my local factors? For the moment I will flush it with fresh fluid and if that doesn't work then all I can think of is to take the cylinder apart and twist the piston slightly so that fresh rubber is pointing back up at the reservoir. Or would that be as likely to work as wrapping magnets round it?

Harry

If it is not leaking, then a strip clean and reassemble may work wonders. A breakers will be the best source of parts or buy a complete car as a spares kit.

mrcheerful