Series 3 Clutch Question

[TJR]

Are you sure you are looking at this right? I think your parts are fine.

Here's a few pics of my new Lucas slave cyclinder. It behaves the same way you descirbe. i.e the piston doesn't return 100% when pushed in. The spring is pretty light weight and I assume it's there to keep "slack" out of the system. i.e. to keep the rod from falling out of center. The hydraulic pedal pressure will move it back when it needs to.

By adding a heavier sping . it's mimicking the actual clutching motion. You will ensure the T.O. brg is in contact with enough force to load the races. Chirping gone.. but would you want the T.O brg spinning all the time? (see my poor sketch below)

Take your spring out and see what happens.

Also using your original parts and given enough run in time, the chirp may lap itself in and go away...









..Talbot

[jac04]

By adding a heavier sping . it's mimicking the actual clutching motion. You will ensure the T.O. brg is in contact with enough force to load the races. Chirping gone.. but would you want the T.O brg spinning all the time? (see my poor sketch below)

Take your spring out and see what happens.

Also using your original parts and given enough run in time, the chirp may lap itself in and go away...

On a S3, the TO bearing is supposed to contact the pressure plate fingers all the time with enough force to keep the bearing spinning at the same speed as the fingers. This is by design, and is much better from a bearing life standpoint than shock loading the TO bearing every time the clutch pedal is pressed. It also helps keep the lubricant distributed within the bearing. The internal spring does keep the 'slack' out of the system, but should also preload the TO bearing enough to keep it spinning with the fingers.

Problem is, on my Girling slave cylinder it is very difficult to push the piston in, and it stays in whatever position I push it to. It will never attempt to return to the outermost position. From your picture, it looks like yours will return almost all the way when pressed in, correct? Is it fairly easy to push in with your finger? If that's the case, then the slave cylinder is operating correctly (want to sell it?).

You definitely do not want the TO bearing to try to 'lap' into the PP fingers. That is what it is doing now, and this is causing the chirping noise. In my situation, it will actually never go away due to 'lapping in', because the TO bearing always returns to a spot where it is just barely touching the PP fingers. It will continue to wear the PP fingers until they fail.

Now, if I take the spring out of the slave, the TO bearing may well be pushed away from the PP fingers between shifts, eliminating the chirping noise. However, this will introduce slack into the system and could lead to a condition where the clutch will not fully disengage on the first pedal stroke. It will also shock load the TO bearing at every shift. Also, the piston is so sticky in the bore that I doubt the TO bearing will ever be pushed away from the PP fingers.

I believe that if I get a properly functioning slave cylinder in there the problem will be solved.

[TJR]

On a S3, the TO bearing is supposed to contact the pressure plate fingers all the time with enough force to keep the bearing spinning at the same speed as the fingers.

On the Slv.Cyl. I have, the piston move easily with finger pressure and does return most of the way. A slight firm tap and it moves on its own a bit further.

As for the T.O brg designed to always be in contact ?? I never looked at it from your point of view. I gues I'm thinking back to my early bronco mechanical clutch linkage which has a large external extention spring that pulls on the clutch fork to release the TO brg and return the pedal to the set height. There's an adjustable rod to set free play. lengthen the rod and the pedal is "topped out" and the TO will make contact, shorten the rod to set the free play.

How do you ever get "free play" on the LR to ensure the clutch isn't held partially open. At the pedal box I guess. I have to assume the Clutch M/C relives pressure back to the resevoir when the M/C piston is returned to the "home" position ?

interestingly...when we used to drive the S3 I'm rebuilding as a family car many years back, my Dad was always telling my Mom to stop resting her foot on the clutch pedal.. , maybe she knew more than we gave her credit for..??

Interesting thread ..

[jac04]

How do you ever get "free play" on the LR to ensure the clutch isn't held partially open. At the pedal box I guess. I have to assume the Clutch M/C relives pressure back to the resevoir when the M/C piston is returned to the "home" position ?

Exactly. Yes, you set the free play at the MC to ensure that the MC always returns "home" & relieves pressure. That way the only pressure on the TO bearing is due to the spring in the slave, which doesn't exert too much pressure at all.

It took me a while to grasp this concept since my old IIA had external linkage at the slave that was used to adjust free play at the TO bearing and my 68 Camaro is mechanical linkage with an adjustable rod & return spring to adjust TO bearing free play.

So, interested in selling me that good Girling slave?

[TJR]

So, interested in selling me that good Girling slave?

It's the only one I have for my rig.. based on this thread figure I should keep it.. If you were closer I'd let you "try" it to see if it solved your problem. It's a few weeks before I go back to CT (my home state) for a visit.

Also , the s.cyl this girling cyl. is replaceing was a cast aluminum housing slave and it worked fine.. though later it totally corroded after sitting unused for so long.

...Talbot

[jac04]

.. the s.cyl this girling cyl. is replaceing was a cast aluminum housing slave and it worked fine..

You know, IIRC every old slave cylinder I have seen has been aluminum. I wonder if the originals were aluminum and they were changed to cast iron later on as a cost savings.

[jac04]

Received the Allmakes slave. Pushed the piston in easily with my finger, and it popped right back out to the original position. Not even a hint of any binding. Hopefully installing it will fix my problem.

However, I'm tempted to try to find out exactly why the existing practically new Girling slave cylinder is binding. Is it a bad bore or a bad piston seal? I might just install the piston/seal assembly from the new Allmakes slave into the Existing Girling slave since they are both 7/8" bore. If that fixes it, then it is definitely a bad seal. If not, then the bore must be out of spec.

For now, I'm off to buy another case of Castrol GTLMA fluid!!

[TJR]

Good Luck.. Would like to hear the results of the component swap..

[jac04]

I finally had a chance to mess around with the new slave cylinder. I thought that the piston/seal from the Girling slave might have been oversized, so I took the piston/seal out of the Allmakes and tried to install it in the Girling. It started into the bore just fine, but would only go in about 1/2" then bind. So, I took apart both cylinders to compare them. I measured both pistons at .873" diameter. The bore in the Girling cylinder measured a hair over .873", while the Allmakes bore measured .876". So, I think that the Girling cylinder is just made incorrectly.

Anyhow, I installed the Allmakes slave cylinder and bled the system. I haven't had a chance to drive it yet, but the clutch pedal feels a little 'lighter' now (although maybe I'm just imagining it).

[jac04]

Update:
Been driving around for a little bit now with the Allmakes slave cylinder & everything is working properly. No chirping noises and the clutch definately has a lighter feel to it now.