Urgent clutch slave cyl question

[Ferret]

Gents,

Just buttoning everything back up this evening and noticed that the clutch slave cylender is automatically extending to full reach.

It's extending in quite a powerful manner as well, I can only just compress it with one hand, is this normal behaviour for the clutch slave? As in, does it push outwards to balance the release springs and stop everything rattling?

Cheers in advance!

:D

[Ross]

Has the pedal been depressed? Open the bleeder to release the pressure, close the bleeder and it should be okay me thinks.

[Ferret]

Has the pedal been depressed? Open the bleeder to release the pressure, close the bleeder and it should be okay me thinks.

Nope, the clutch pedal hasnt been touched since I took the car apart, I'm wondering if it's something to do with why the clutch has burned out. Will try bleeding up the system tomorrow and see what happens.

[yaofeng]

My guess is you may have accidentally depressed the clutch pedal without knowing. If you only removed the gear box. You don't even need to bleed the clutch. Is there a reason to do it? I think that is why hanging by itself detached from the gear box the push rod extended without resistance provided by the release bearing on the clutch.

[attack eagle]

x2

[Ferret]

My guess is you may have accidentally depressed the clutch pedal without knowing. If you only removed the gear box. You don't even need to bleed the clutch. Is there a reason to do it? I think that is why hanging by itself detached from the gear box the push rod extended without resistance provided by the release bearing on the clutch.

I *know* that the clutch pedal hasnt been pressed... you reckon it's gravity feeding then?

[yaofeng]

It is possible gravity may have extended the pushrod out. But I cannot confirm. One time I accidentally depressed the clutch pedal while the slave was hanging outside of the gear box after completing the 525 clutch. The pushrod shot out of the slave together with the end cap. Both fell to the ground. I had to recrimp the edges of the slave to seal the cap.

[bsell]

I *know* that the clutch pedal hasnt been pressed... you reckon it's gravity feeding then?

How about the clutch pedal rod is adjusted too long, causing the piston inside the clutch master to cover the access hole to the reservoir. Then there is no place for the expanding fluid to go but push back on the throwout bearing.

You know, this inability to flow fluid back to the reservoir as the slave heats up could have taken out the two year-old clutch job...

The way to eliminate my hypothesis is to undo the clutch pushrod from the pedal and see if the master cylinder pushes back a little and your run-away slave calms down. This should be a quick and easy experiment.

I figure there is some spec for the pushrod adjustment but I don't know it...sorry!

How did the flywheel clean up with the sandpaper and water trick?

Brian

[Ross]

Sounds like a winner. I'm pretty sure Ferret was fooling around with clutch adjustment too.
http://www.bimmernut.com/forum/showthread.php?t=38792

[yaofeng]

How about the clutch pedal rod is adjusted too long, causing the piston inside the clutch master to cover the access hole to the reservoir. Then there is no place for the expanding fluid to go but push back on the throwout bearing.

You know, this inability to flow fluid back to the reservoir as the slave heats up could have taken out the two year-old clutch job...

The way to eliminate my hypothesis is to undo the clutch pushrod from the pedal and see if the master cylinder pushes back a little and your run-away slave calms down. This should be a quick and easy experiment.

I figure there is some spec for the pushrod adjustment but I don't know it...sorry!

How did the flywheel clean up with the sandpaper and water trick?

Brian


I don't remember anything adjustable on the clutch pedal when I removed it during the 6 speed conversion. Everything seems to be bolt hole to bolt hole. Am I missing something?

http://i21.photobucket.com/albums/b274/yaofengchen/BMW_95_540/DSC_3233.jpg

http://i21.photobucket.com/albums/b274/yaofengchen/BMW_95_540/DSC_3242.jpg

http://i21.photobucket.com/albums/b274/yaofengchen/BMW_95_540/DSC_3243.jpg

http://i21.photobucket.com/albums/b274/yaofengchen/BMW_95_540/DSC_3237.jpg

[Ross]

Oh my you did that the hard way.
The rod length is adjustable at the clevis. Or is it?

[yaofeng]

Oh my you did that the hard way.
The rod length is adjustable at the clevis. Or is it?

I don't see how it can be adjusted. I am sure I would have noticed if it were.

[bsell]

Oh my you did that the hard way.
The rod length is adjustable at the clevis. Or is it?

O.K., you caught me talking out my behind. I ASSumed there was an adjustment and was too lazy to look on RealOEM.

So I had a look see and can't see anything related to the clutch pushrod being adjustable on RealOEM.

So off to the Bentley manual (searchable version, found here posted up by some very nice person:)) and I found this on page 210-2:

Check the clutch pedal height as shown in Fig. 4. If the pedal adjustment is incorrect, loosen the eccentric bolt nut and rotate the bolt 180 [degrees] (dot facing the master cylinder).

NOTE - Note the position of the "dot" on the head of the eccentric bolt. The dot must be facing either toward the master cylinder or away from the master cylinder, but not in between.

And the adjustment spec:

Clutch Pedal Adjustment
• Pedal face to bulkhead . . . 265+10 mm (10.4+0.4 in.)

Not the threaded arrangement I figured but an adjustment to be screwed up either way. Go and figure the German engineers prescribed preset adjustability. 'They cannot be trusted' (said with a Bavarian accent :p)

I think this call for more "Ferret on his back time..."

Brian

[yaofeng]

Guess I missed it. But it turned out alright by sheer luck. Looking back at the pictures I took. I may have caught a glimpse of the eccentric bolt mentioned in Bentley by accident which I completely ignored.

The eccentric bolt is lying at the tip of the master cylinder in the picture I think.

http://i21.photobucket.com/albums/b274/yaofengchen/BMW_95_540/DSC_3234.jpg

[Ferret]

Guess I missed it. But it turned out alright by sheer luck. Looking back at the pictures I took. I may have caught a glimpse of the eccentric bolt mentioned in Bentley by accident which I completely ignored.

The eccentric bolt is lying at the tip of the master cylinder in the picture I think.


Haha, okay now I have the total opposite problem :D

I suspect either the slave or the master cylender are on the blink - after bolting everything back together and there was a shed load of air in the slave cylender. The pedal was just sinking down to the floor.

Bled it up and now it's very light for the first inch of travel, and only releases fully 1cm above the bulkhead.

I think it's because I've bled it up with the nose end of the car right in the air, and the bleed nipple is on the back end of the cylender.

I'm going to flush it again tomorrow with new fluid and the arse end of the car higher than the nose. Other than that, the whole clutch job's gone spectacularly smoothly - apart from some idiot putting the shift lever in backwards :D going to have to sort that out tmr evening.

It's all working now and the clutch is solid, been out driving it around and no slipping.

The super fine emery paper trick worked a treat - took all the glaze off the surface of the flywheel and left it with a smooth, non slip surface.