High Clutch Actuation

[rowleyman]

Hi Guys,
Just spent an excellent 2 hours browsing the forums. I have a 1964 3.8 series 1 soft top. The gearbox and engine are out of the car and I am resolving issues 1 by 1. I am stumped by the fact that the clutch only engages drive right near the top of the pedal travel. The clutch is a 10" plate with the dry plate Borg and Beck cover (code 10A6-G. I believe it is also refered to as the horizontal spring clutch as there are 12 spings rather than a diaphragm. The clutch platet looks fine with virtually no wear, the slave cylinder is the correct ? 80mm long version (C21470). There is no return spring fitted. I beleive I set up the free play on the actuating arm correclty. Is there anything I am missing here?

[Heuer]

Welcome to the Forum.

There should be a return spring with that slave cylinder although I am not sure that would make a difference but you should really start with a fully standard setup. You also need to make sure you have the correct actuating rod for that slave (part 23 in the diagram) as the later hydrostatic slave cylinder uses a different one (and no spring).



No doubt others here may be able to offer further advice.

[PeterCrespin]

You may have the wrong release bearing as the depth varies between 3.8 and 4.2 and your symptom is what happens when the clutch is worn. With a worn clutch the contact rubbing face for the carbon bearing moves backward.

I've never actually tried the wrong clutch parts to see what happens and if it gives the symptom you describe, but I could believe it would depending which way round your parts were mixed up.

You're welcome to the multiple coil spring clutch. It's no accident that diaphragm spring clutches took over...

[kingzetts]

If I've understood your problem correctly, the clutch is engaging OK with the pedal released but disengages with the very first bit of pedal movement. This can possibly be caused by the lack of a return spring. When you release the clutch pedal, the release arm (driven by the clutch cover springs) will push the slave cylinder back only until the clutch is engaged. To generate the free play, the return spring then pulls on the operating rod which results in the slave cylinder being pushed further back in the cylinder bore. In the absence of the return spring, the slave cylinder can sit in the wrong place, with no free play, so that when you press the pedal the initial movement which usually takes up the free play instead results in immediate movement of the release arm. When you push the operating rod back to adjust the free play, you are mimicking the action of the return spring. So with correct free play but no return spring you could well have the symptoms you describe.

[paulj]

Hi
I have recently rebuilt a 2+2 the clutch slave cylinder
turned into a monster
no seemed to knw which rod was correct for which cylinder
20 answers on using the return spring or not
also not entirely sure i got the right release bearing!
I ended up measuring the distance required and at rest
and made a push rod to suit which works fine and has done for the last 1500 miles
hope this helps
regards Paul

[Heuer]

Either the original or the later hydrostatic slave will work but you need to opt for one or other system, not a combination. The hydrostatic system is self adjusting and does not require the return spring so is probably the obvious choice unless you want originality or have all the early parts already. I actually moved back to the original 'short' slave but only because I could not find a repro hydrostatic unit that did not leak. Others have tried a rebuild with the same result (seals of Chinese manufacture) so in the end I searched eBay and found an original Girling NOS unit. It did mean modifying the actuating rod and buying the spring but at least it works reliably. I agree with you about getting the correct matching parts though - suppliers are a nightmare in this respect.

[ChrisC]

Out of interest chaps - does the clutch actuating fork have any free play when at rest (i.e. clutch pedal in the normal position)?

Mine has no free play at all so I am now worried that my clutch is slightly engaged all the time but I am still weeks away from being able to start the car to actually find out.

[Heuer]

[ChrisC]

Thanks Dave

But what i was really asking is how much free travel does the fork have (if any) BEFORE you do any adjustment with the slave cylinder rod.

i.e. if i remove the slave cylinder completely - does the clutch fork move at all.

I just wondered if my clutch has a problem waiting to kick me at a later date when I come to use it. Although it was fine when I took it off.

[PeterCrespin]

If your slave is not fitted the fork flaps around. It will move freely between forward as far as it will go, to far enough back to touch the realease bearing on the clutch.

You are worried about the clutch always being partly DISengaged, not engaged, if you have no slack. In practice, if you have the hydrostatic system and your clutch pedal return spring is OK, the fork comes to rest at a point of zero pressure in the cylinder. The release bearing can be *very slightly* kissing the clutch but this is OK . If you worry then a light return spring (not heavy enough to overcome the slave piston return) will ease your mind though it's not essential.

Pete