Clutch knocking noise

[zigzagsky]

Had a problem a couple of weeks ago with the clutch slave cylinder having a small leak. Bought a new slave cylinder and was moving the car when it suddenly let go completely. Luckily the car was only a few feet from my garage and I put her in first and used the starter to move the 8-6 feet into the garage and on to my small scissor lift.

However, this may have not been a good move as after fitting the new cylinder there is a knocking noise now coming from the bell housing which generally goes away when the clutch is depressed.

I've removed the starter motor and that seems ok and rotated the engine looking at the flywheel teeth and they also seem ok. Had a look through the small inspection hole in the bell housing but cannot see anything obvious.

I guess that it's engine and gearbox out to find the cause but does anybody have an idea what it might be?

It's a Series 2, 2+2 so I assume I cannot remove the gearbox without removing the engine. Given that I have a small scissor lift, would it be better to drop the engine rather than lift it out?

Feel pretty stupid as I suspect that moving the car on the starter is what caused the problem but I've done it with cars in the past with no ill effects and it was only a short distance.

I've tried to attach an MP3 of the noise but the file type is not allowed. May be able to PM or email it if useful.

[cactusman]

Hard to imagine why moving the car on the starter would cause a clutch issue. I have done it to mine more than once with no ill effect. I would start by peering at the new slave installation. It is a tightish squeeze. Are you sure it is not the new slave or associated pipes that are tapping somewhere they should not? Just a thought....Best eliminate the easy to fix before thinking of getting the engine out

[zigzagsky]

Definitely not anything external knocking. The noise is coming from within the bell housing. Using a screwdriver as a stethoscope it may be slightly louder towards the front.

The noise is related to engine speed and generally disappears when the clutch pedal is depressed.

[Series1 Stu]

Hi

If the slave cylinder has let go could this be allowing the clutch release bearing to knock against the clutch pressure plate or it's back stop?

Regards

[zigzagsky]

Thanks Stu.

I've replaced the slave cylinder and bled the system and the noise is still there. Is it possible that it is a mis-adjustment of the actuation rod that might be causing it or could the release bearing have shifted?

[PeterCrespin]

I've replaced the slave cylinder and bled the system and the noise is still there.

Is the slave held on by studs or bolts/set screws?

It sounds as if the fastener(s) are protruding too far inside and kissing the clutch cover. Is it the original S2 4.2 bell or has the car been converted from an auto to manual? Is it a diaphragm clutch or coil spring type, and what size? Should be diaphragm 9.5" clutch.

[phil.dobson@mac.com]

take the slave off and ensure the release bearing operating lever is as far forward as possible (away from the clutch) if the noise is gone you can start to eliminate things. if not.......

[zigzagsky]

Thanks for the replies chaps.

The slave cylinder is held on with studs and is the one that is 95mm long with no return spring.

The car hasn't been modified as it was an original RHD manual so as far as I know, it's the original bell housing.

Not sure what the clutch type or size is - I assumed a diaphragm type being a Series 2?

I'll try the idea of removing the slave cylinder and moving the release lever forward and update you,

[mgcjag]

Hi Brian...think you should be useing a return spring to keep the fork/pushrod pulled back and adjusted with the correct gap... Steve

[E600]

I would check that the slave cyl studs did not enter the bell housing space when you fitted the new slave cyl. I would recommend buying one of those flexible cameras and feed it into the bell housing, with engine off!

Look at the two studs on the inside of the housing and a good look around the CR Bearing

Best of luck

Pat

[zigzagsky]

Interesting to hear that the spring should be fitted. I guess the easy way to check if that might be the problem is to manually pull the release lever back?

The studs were not removed when I took off the slave cylinder so I cannot see how they would have moved during the change.

I'll take another look and try out a couple of the suggestions tomorrow.

Thanks for all the help and advice so far.

Brian

[zigzagsky]

Unfortunately due to the fact I spent all of Saturday taking part in the JDC Annual Rally, my other half decided that Sunday was 'gardening day' so no chance to look at the car again until next weekend.

[Hugo]

It sounds as if the fastener(s) are protruding too far inside and kissing the clutch cover.

If that is indeed the case, you might want to have a look at crankshaft end-float. If depressing the clutch makes it go away it suggests the crank is moving forwards. Long shot but I have seen it happen once (on a Triumph 2000 - the crank was moving about 3/8" and it was so bad it was stopping the clutch from disengaging).

[zigzagsky]

Thanks Hugo.
I guess it could be excessive end float but why did it happen all of a sudden? Up until the time the slave let go it was all tickity boo.

Hope to get a chance to address the issue further this weekend.

[1954Etype]

If the crankshaft thrust washers are fitted the wrong way round, they will wear both the crank and washer very quickly. Put your foot on the clutch and see if you can detect movement on the crankshaft damper.

[Hugo]

Thanks Hugo.
I guess it could be excessive end float but why did it happen all of a sudden?

No idea! It's a long shot, but easy to check and eliminate. Does the pedal feel the same as it did before? Does the noise occur when you start pressing the pedal or when it is fully depressed? Just possible (an even longer shot) that you might be getting more travel and something inside the clutch is fouling, although that wouldn't happen till you put it in gear & the centre plate stops spinning.

[zigzagsky]

The noise generally only occurs when the pedal is not pressed. So does that sheds any light?

[BRM]

Here's another thought, for what it's worth.
You say the old slave failed completely and suddenly. If it went with a bang maybe the shock was enough to snap one of the fingers of the clutch diaphragm if there was a weakness there. This could leave it rattling around loose when the engine is ticking over but depressing the clutch would put pressure on it and stop it rattling.

[Hugo]

The noise generally only occurs when the pedal is not pressed. So does that sheds any light?

I had it the other way round - could be just the release bearing rattling against the pressure plate? Does it or did it have a spring? Does the noise stop when you rest your foot on the pedal, or only when it is depressed?

[zigzagsky]

Done some more investigating today.

So I have removed the slave cylinder and the noise remains even with the lever arm held firmly back (away from the engagement point if that makes sense). I have already bought the return spring and mounting so will fit it anyway.

'Resting' my foot on the clutch pedal does not affect the noise, it really only disappears when the clutch is being properly engaged.

Using a rudimentary stethoscope, the noise seems to be from the forward part of the bell housing, not the rear so I guess that at least probably means it's clutch related.

Without the clutch slave fitted, there is a lot of 'free play' on the lever. generally it sits about a third of the way along the slot in the housing when in the position where the slave cylinder would start to engage the clutch. The free play is back as far as 2 thirds. I have noticed that without the slave fitted, if you hold the lever against the clutch, you can feel and see a little bit of vibration so maybe it is something related to the arm itself? Although it doesn't feel 'solid' as though it's being hit by something rotating.

I looked through the rear inspection hole in the bell housing with the engine running and you can see the pressure plate spinning. It does seem to have a slight wobble but ever so slight.

Any more ideas? I think its getting more and more likely that the only way I'm going to fix this is to take the drivetrain out and split it!

Shame it's proving to be such an issue to find the cause as we have yet another rally tomorrow and the weather is supposed to be good!