Clutch Hydraulic Issues

[RichardsonStag]

Right, so i was on here a long time ago but my old account seems to have died, therefore i'm back with a fresh account.


We've just finished reassembling our Stag after replacing the clutch to find the hydraulics of the clutch master/slave arn't working. They were working fine when it was last driven (August) however at that time the clutch slipped on every hill so the car was laid up to have its clutch replaced.
The old clutch was extremely worn (looked possibly original) so it definately needed replacement. We did not disturb the hydraulic side of the clutch release mechanism since we didn't need too therefore we can't understand why it won't work.

The symptons are:
-the clutch pedal moves freely and springs back up, but doesn't feel like its doing anything (which it isn't)
-the slave cylinder (replaced about 6 years ago) is pretty much at its full extent, it can easily be pushed back in with the rod that attaches to the clutch release arm however it will slowly push itself back out again without us doing anything
-most importantly pushing on the clutch pedal does not create any movement at the clutch slave end

We have bled the hydraulics, no bubbles came out and there was no difference, theres plenty of fluid up in the reservoir.
The clutch release arm moves freely on the gearbox, you can hear the release bearing touch the clutch pressure plate at one extent and then hear the 'clunk' when its back out the way.

So thats it really, we're thinking that the clutch master has possibly died but before we go shopping for a new one some experienced advice would be much appreciated

Thanks,
Mat.

[StagnJag]

Is the clutch slave cylinder attached on hte right side? The main body of the slave cylinder should pass through the mounting hole. The replacement I bought had the flange machined on hte opposite side and I initially fixed it on the wrong side. It worked initially and then let me down when I was out and about and had to be transported home. It may be that the new clutch has caused the slave cylinder to just not quite have enough travel to disengauge the clutch.

Rgds

Dave

[Firept]

Mat.
There must be something in the air I am having the same problem.
Finished using the Stag in Oct / Nov ready for a complete overhaul of engine and gearbox so of course replace the clutch while it was out as it was still on the original.
Rebuild all went OK and now back in. I did rebuild all of the hydraulics late 2010 so has been working fine with no problems so replacig it should have gone smoothly but no the clutch still does not push the operating arm far enough I have about1/4" of travel before it engages and it does appear that it still needs bleeding has a strange "feel" about it. I have been advised on here that you need to make sure that the bleed nipple is at the top on the slave so that the air cannot get trapped so this is my next move to unbolt the slave cylinder and feed it out of the bell housing if I can, then with the whole cylinder vertical and the piston held fully in bleed the system again. If this does not work then any one got a good design for a cable operated system?

Paul.

[richardthestag]

what he said about the slave being mounted the right side of the engine plate^^^

Plus make sure that the slave is installed the right way up, does the bleed n ipple have to be upper most? can't recall but it won't bleed if the wrong way round.

I had a failed master on my car which would bleed the fluid but when nipped up would not move the push rod in the slave, it was a brand new unit. I checked it out and could find nowt physically wrong with it, a replacement had it all back to full rude health.

What worries me slightly is this bit "the slave cylinder (replaced about 6 years ago) is pretty much at its full extent, it can easily be pushed back in with the rod that attaches to the clutch release arm however it will slowly push itself back out again without us doing anything"

with no hydraulic pressure the clutch cover should push the clutch plate back onto the flywheel and in turn push the carrier and release bearing back towards the gearbox. This action alone on a good system would ensure that the slave pushrod is returned back to its rightful place. it the carrier is stuck on the gearbox input shaft or the clutch plate is stuck on the splines then there is nowt to push the slave pushrod back and the hydraulics will fill the gap in the slave.

I know been there done that and have the missing knuckles from 'avin the gearbox off twice in as many weeks.

Check the easy stuff first, if it were me I would be keen to check that the clutch plate was engaged. i.e. stick it in first gear and turn the starter does the car lurch (be careful not to hit anything wont you?!?), if not then I think you may have a more serious problem. If it does then start looking at the release mechanism. can you move the crosshaft easily? bear in mind that it should be angled slightly towards the slave but shouldn't get beyond the vertical when the clutch is disengaged. If you can swing it back and forth with ease then it is possible that it is no longer attached to the fork that pushes the carrier back and forth.

My car had dodgy sticky splines. the clutch plate was sticking in slightest crud in the splines, I could pull the cross shaft towards the front of the car and take up slack in slave. the next time the clutch was depressed by my assistant it was nice and light. only the cross shaft didn't spring back towards the slave when the clutch pedal was let go. the next time the clutch was pressed it would start from the slipping clutch point and then try force the clutch release more that it should go.

the fix for me was gear box off, thoroughly cleaned out the splines on the gearbox using a very small flat blade screwdriver so that I could make the cluch plate move up and down the splines smoothly using gravity (i.e. tilting the gearbox one way and t'other on the bench) next I ensured that the release fork was free from wear and fitted the grove on the carrier with no snags. The carrier is made from butter and I found that I had to widen the grove in a couple of places to make the release fork pins move freely. Then I used some copper ease on the moving bits and reassempled. Happy days and a dead light and happy clutch feel for me.

Regs

[Mike Stevens]

If you get no slave travel when you press the pedal, this implies there is no fluid movement. If there's no fluid movement then you probably can't bleed the system anyway! When you bled it, did you get a good stream of fluid out?

I would be tempted to disconnect the pipe at the slave and see if you can push fluid out, preferably with some back pressure, (finger over the pipe end!). It will be messy and don't get any fluid on the bodywork.

If this doesn't move the fluid properly, then it suggests that the seals in the master cylinder are letting the fluid past under load and not pushing it out.

The slave cylinder must be fitted with the bleed nipple above the inlet - otherwise you won't be able to get all the air out!

Cheers,
Mike.

[DJT]

It will be messy and don't get any fluid on the bodywork.

Or in your eyes. It hurts and can require a visit to A&E. BTDT.

Dave

[StagnJag]

...

What worries me slightly is this bit "the slave cylinder (replaced about 6 years ago) is pretty much at its full extent, it can easily be pushed back in with the rod that attaches to the clutch release arm however it will slowly push itself back out again without us doing anything"

...

Regs

Assuming that the pin is not connected to the cross shaft, this is normal behaviour. There is a spring inside the slave cylinder. Pushing the pin in will displace the fluid back up into the reservoir. Make sure you haven't inadvertently spilt fluid down the bulkhead.

Rgds

Dave

[V Mad]

My expereinces with hydraulics has been that this can happen when the master cylinder is renewed and completely dry inside. The fliud does not flow into the piston cylinder however much you pump. I have found that priming the cylinder first gets it going (take out the piston and pour in some fluid). Another technique I use is to undo the nut on the outlet until the fluid comes out under gravity. Maybe it is caused by an airlock, but whatever is the cause it does work. Once you have primed, pumping the pedal will push fluid out under pressure and you can then bleed as normal.

[RichardsonStag]

thanks for the replys chaps.

Nope we havn't spilt any fluid, i know what wonderful stuff it is, there was a steady stream of fluid when we bled the system, it was vary dark (dirty?).

richardthestag what youre suggesting is the clutch itself isn't working properly right? What i meant with my comment is you can move the clutch release arm on the side of the gearbox freely (i.e. it isn't seized), you can feel it touch the pressure plate fingers and go back to the furthest away position (release bearing as far away from clutch as possible). I didn't try releasing the clutch with the arm since surely it would take a considerable amount of force to do by hand?
The clutch is engaged, it wont turn over at the moment (dead battery) but its parked on a slope, once in gear (with the handbrake off) it won't roll away.

However one point is that iirc the slave cylinder is fitted from the engine end, i.e. the main body does not pass through the mounting hole, so theres something to be rectified. I was wondering in my mind why the slave was pretty much at full extent when the clutch wasn't even disengaged. I'm pretty sure the bleed nipple was to the side of the hydraulic hose but i'm probably wrong, if i'm wrong then i'm sure its below the hose so i'll spin it round by 180degrees when i swap it to the other side. A few of you pointed this out and it makes complete sense now i think about it!

My main concern is that the hydraulic side of the clutch was perfect when the car was parked up, we purposely didn't touch that side of things and it now does bugger all when you press the pedal

I'll swap the slave around with the bleed nipple the right way up next time i'm with the car and will come back with an update

Thanks,
Mat.

[4x4]

For me the key statement here is that there is no movement of the slave when the pedal is pressed.
Forget all other issues until this is fixed.
Yes - make sure the bleed screw is at the top.
Yes - I'd agree it could be airlocked - I get rid of mine the same way as was suggested - undo the outlet pipe and let gravity do the rest.

I have found that it's best to bleed the clutch without wasting too much time.
If there's air in the line, you need to keep it moving.
If you're bleeding single handed and stopping to top up the master cylinder, air in the line can just float back to the top again - a vicious cycle you cannot break.
Get a proper one way valve attached via tubing to the slave bleed nipple, get someone else to keep pumping the pedal (not at a crazy speed) and keep topping up the master cylinder.


Good luck!

[StagnJag]

I have always wondered if it would be better to bleed the clutch from the bottom up, force the fluid in through the bleed nipple until it fills up the reservoir. Should eliminate all air from the pipes.

Never tried it to test the theory though!


Rgds

Dave

[dasadrew]

Not tried it out yet, but I'm hoping this device will be the panacea for all air-in-hydraulics problems. Anyone used one?

http://tools-from-germany.com/index.php?page=product&info=2116

Cheaper than maintaining a WAG to pump the pedal!

[Tonyw]

Hi

I had the same problem when I reinstalled my engine a month ago. We refitted the clutch slave and master cylinder but could not get a pedal to release the clutch. We used a pressure bleeding unit like Drew has suggested (gunsons) and the pedal came back with the clutch operating fine. The next time I went to the car I had to do the same again!!
When I left the car for the second time I fitted a piece of wood in between the seat base and the clutch pedal to hold the pedal down (about a week) as I had read somewhere that this works??

Lo and behold it did work and I have had no problems with the clutch since.

I hope this may help with your problem.

Tony

[Firept]

Just borrowed on of these from work to see if it will help but its too cold wet and dark now, I will see if I can get on it tomorrow evening and I will let you know if it works. (they are a lot cheaper on eBay!).http://www.thetoolboxshop.com/68714-...kit-6397-p.asp
Paul.

[flying farmer]

It doesn't matter which way up you fit the slave cylinder, the pipe and bleed nipple are positioned horizontally which is why you have to remove the cylinder mounting bolts and turn the cylinder through 90 degrees before it will bleed properly, and you will get an extra bubble of air out if you push the slave cylinder piston back into its bore before you close the bleed nipple.
If the pushrod is at full travel the odds are you have the slave cylinder mounted the wrong side of the engine plate
Non of this will matter if the master cylinder is not pushing any fluid, however if the problem is air trapped in the pipe then holding the clutch pedal down for a while, by leg or broomstick, will allow the air to rise to the highest part of the clutch pipe. On releasing the pedal this can then shove the air back into the master cylinder
I have three stag engined cars with manual boxes, I have had plenty of practice over the years!
Neil