Herald clutch woes

[nonotatall]

First post here..clutch problems...

Over the past six months the clutch has been gradually becoming unusable, it would only disengage when you put your foot nearly through the floor and increasingly some pumping was also required.  Always amusing when stuck in the middle of a box junction.  it was not the clevis pin as that was the first thing I changed, the fluid was black so I suspected a dodgy seal somewhere.

Finally last weekend I got around to changing the seals.  I did both master and slave cylinder and flushed through the pipe.  When putting it back I managed to cause the pipe sealing nut on the slave cylinder to cut a new threads in the softer aluminium of the slave cylinder...oops. I decided it was not going to be fixable easily so I called my local motor factors place which by some miracle had a spare slave cylinder.  I had to modify this a bit because the old one had a new slot ground out to fix it in place as the release arm pushrod was a bit short so I copied the slot onto the new one.  Filled up, bled off and it all seemed fine, on a test drive after about 10-15 actuations of the clutch the pedal became heavy and then impossible to push.  After pushing the car back to the garage I bled off the system, filled up again and it seemed to work again but was now quite stiff.  I drove around the block about 10 times untl it was good and hot, seemed OK so I set off home from my friend's garage where I'd been doing the work.  about 5 miles down the road the pedal again became stiff and seized, this time there was also a bit of a squeal until I turned the engine off.  This required a call to the AA... for a tow...3 hours later.

The curious thing is that the fluid in the reservoir was again black and opaque where it was nicely clear and yellowish only an hour or two before.

I didn't check the 'new' slave cylinder seals and my guess is that they may have been on the shelf for a decade or two and may have perished.  My more grave concern is that after replacing the seals the more positive and greater travel of the slave cyl piston might have pushed a bit harder than the release arm/bearing was 'used to' and may have messed it up in there.  The dark fluid gives me hope that it will not require the more major undertaking of a clutch replacement... not something I feel particularly able to do.

I'd appreciate any diagnosis hints, I'm going to strip down the 'new' slave cylinder tomorrow and try not to cross the threads putting it back on this time.

[thescrapman]

I suspect the new slave didn't need the extra slot cutting in it, as that is a common bodge to get round the pedal biting too low, usually caused by the pin dropping out.

The slave pushrod can't be too short as it is attached to the release arm.

There are different slaves for spring and diaphragm clutches, so that may be the issue.

When you say the pedal went stiff, was that with the clutch then dis-engaged?

Cheers

Colin

[nonotatall]

Thanks for replying Colin, I'm Tom by the way.

I had that suspicion too (about the slot) but the cylinder would not work with the securing pin in the 'proper' slot, like that the pedal just stopped hard about 2 inches from the floor.  I presume that in that situation the rod on the release arm was dropped down and the piston in the slave cyl was just pushing the side of the bar not the end downwards and it desn't drop down very far, if you see what I mean (I can post a sketch if not).

Which dropped out pin are you refering to about the bodge?  the pin of the release arm? the pin of the pedal?

The stiffness in the pedal was odd, it was fine for one actuation and then when released it seemed to return slowly (sucking through lots of fluid from reservoir?), it then was stiffer for maybe one more actuation, again returning slowly and then it was totally jammed up, the squeal I heard seemed to happen when I pushed a little on the jammed pedal.  It is all a bit difficult to remember in detail as I was driving along at the time (the second time trying to stop at lights) and so I was concentrating on the road a bit and also feeling a little depressed that I'd fixed one problem only to make another, ain't it always that way?

Didn't include details of car at the top: 13/60 saloon 1968, diaphragm clutch I believe.

[heraldcoupe]

When the clutch is working (ie unseized), is the release point low or high? The gradual stiffening is a symptom of a failing master cylinder spring, so not fully releasing pressure in the system as the pedal returns. With this I would also expect gradually increasing clutch slip, any signs of that?
Cheers,
Bill.

[nonotatall]

Hi Bill, thanks for replying.

The release point was obviously low before I changed the seals, afterwards it seemed pretty much where it should be, i.e. somewhere in the middle.  It might have been a bit high but it is difficult to judge.  The slave cylinder spring seemed OK during the reseal (it sent the little seeal at the end catapulting accross the garage) but I guess a lack of suficient springiness might not have been that obvious.

What do you think about the suddenly dirty fluid? 
Do you agree with my diagnosis that this might indicate the 'new' slave had perished seals? 
Would perished seals in the slave make the pedal feel heavy and sieze it?

Sorry for all the questions but I'm just hoping that it is just the slave cyl and I don't have to take the gearbox out change the clutch etc... Especially as now I'd be doing it on the street.

Sorry, nearly forgot, no signs of clutch slip at any point, only clutch spin (not fully disengaged) before I changed the seals, this went completely after the seal change for the 50-100? times it worked before seizing.

Cheers

Tom

[heraldcoupe]

[quote by=nonotatall link=Blah.pl?b=hervit,m=1154954925,s=4 date=1154964352]The release point was obviously low before I changed the seals, afterwards it seemed pretty much where it should be, i.e. somewhere in the middle.  It might have been a bit high but it is difficult to judge.  The slave cylinder spring seemed OK during the reseal (it sent the little seeal at the end catapulting accross the garage) but I guess a lack of suficient springiness might not have been that obvious.[/quote]

It's the master cylinder spring which causes system pressurisation, the slave cylinder spring is unlikely to be a problem.

Quote:

What do you think about the suddenly dirty fluid? 
Do you agree with my diagnosis that this might indicate the 'new' slave had perished seals? 

As you have rebuilt the master cylinder and cleaned the system, that is almost certainly the case

Quote:

Would perished seals in the slave make the pedal feel heavy and sieze it?

If the seals were swelling excessively then that is possible. It's just occurred to me that an old-stock cylinder may have seals designed for Dot 3 fluid, modern seals are fine with Dot 4.
Try sticking in a set of replacement seals, unfortunately you will need to do this to both cylinders now as the new master cylinder seals will have been contaminated.
Cheers,
Bill.

[nonotatall]

Sorry Bill, I meant master cylinder spring and not slave cyl.

OK, I'm glad you agree that it might just be the slave cylinder and it is interesting what you say about DOT3, it could make sense.

I originally ordered two seal kits for slave and master cylinders as I thought I might need them. So I should be able to have a go one evening this week.

Let's hope it is just the hydraulics as I don't really have the cash for a new clutch and also think it might be beyond my ability to fit.

I'll post back if I know more, thanks for your input, don't let me stop others suggesting in the meantime though.

Cheers

Tom

[nonotatall]

OK, I took out the slave cylinder without detaching the hydraulics and found the pedal would still not depress even though it was not pushing against anything.  I surmised it must be seized.  Strangely the pushrod of the clutch release arm had a semi-circular score mark on the end of it, I'll come back to that.

I detached both cylinders and flushed through the pipe.  I then cleaned out and resealed the master cylinder.  Finally, I disassembled the slave cylinder.  Remember that this cylinder was brand new the other day (shiny new out of a yellow girling box).  The bore of the cylinder was fairly scored and the piston that clearly had previously been coated (anodised?) with black was also worn.  The wear on both piston and bore suggested that the piston had been travelling back and forth not fully centered.

From this wear and the score mark on the pushrod I think what had happened was the pushrod must have dropped down and was being pushed by the edge of the 'bowl' at the end of the piston, it was probably wedged partly in between the edge of the piston and the piston bore and the edge of the piston had put the semi-circular mark on the pushrod end. I imagine that this is what caused the stiffness (the metal grinding) and the black fluid was probably from the anodised stuff on the piston coming off (might have also been the seal but it looked OK). The seizing would probably have been the wear have finally causing the piston to jam off centre.

I used 1000 grit wet and dry paper to get the score marks out of the cylinder bore and then I put a new seal on the piston and reassembled the slave cylinder with the spring etc...

To make sure that the same problem did not happen (the pushrod dropping down) I filed the second (new) slot that I'd made back a bit further (away from the clutch) so that the cylinder would go 2-3mm further in (any more and there would not have been enough aluminium).

I reassembled the whole thing and bled it making sure that the cylinder was as far in as possible. (a tap or two with a mallet with the bolt in).  The clutch was stiff for a couple of goes and then seemed fine.  I drove around and around the block about 20 times (remaining uphil!) and it seemed fine so I think it is OK as long as the pushrod does not drop again.....  I should probably do the whole clutch and fit a new pushrod etc... but for now I have to do the brakes, rear suspension, dampers..... and it is also due an engine service..... it will have to wait, thanks for your help.