Clutch Slave Cylinder Assembly

[TR4ffic]

So... Just carrying on from my gearbox thread.

Clutch:

I’ve been plagued by a clutch with a variable bite point for ages with adjustments and bleeding making no improvements, so I’m hoping to investigate/remedy this whilst the ‘box is out… I found that the Clutch Slave Cylinder and the actuating arm on the Clutch Operating Shaft weren't aligned and I'm wondering if this has been causing the variable clutch operation problems I've been experiencing...

Peter W said '...It looks like the cylinder is fitted to the rear face of its mounting plate, whereas it should be on the front face, or engine side.   That is because it is a Girling system not Lockheed.   That will mean a longer pushrod is required, when fitted correctly.  The angle the push rod is at will also improve.'

Although not shown in the above photo, just to confirm that as I found it the Slave Cylinder Bracket was fitted on the rear side of the 'box bellhousing flange and the Slave Cylinder itself is mounted on the rear side of the bracket - so the Slave Cylinder is closest to the clutch actuating arm.

These are the Slave Cylinder and Push Rod I have...

From Peter's comment and looking at the Moss catalogue, I need to swap the cylinder onto the other side of the bracket ...but do I have the correct Push Rod?

...and is there any easy way of checking I have the later Girling Slave Cylinder Bracket? ...or are they not interchangeable?

Lastly, and for completeness, the gearbox number is TS 18643 ...earlier than my TS 78126 car. Can this add to the Clutch Slave Cylinder/Actuating Arm alignment issues?

Apologies, lots of questions...

Any feedback much appreciated.

Nick

 

[BlueTR3A-5EKT]

Are you positive that the master cylinder is not bypassing fluid internally, causing the pedal height changes?   Or just simply needs bleeding?

You will need to re bleed the clutch hydraulics after disconnecting the slave from its hose and fitting it the correct side of the bracket.   So buy yourself the two seal kits and reseal both master and solve cylinders of the clutch.

Moving the cylinder to the front face of the bracket will see an increase in rod length equal to probably 7/8”.  ie. The bracket thickness plus the cylinder flange thickness.   That amount of adjustment can be checked on what you currently have fitted.   Worse thing that can happen is that you have to replace it.  Shout if you need one.   One of us must have one somewhere.

[TR4ffic]

Hi

Again, thanks for the feedback Peter. 

I bled the clutch system last year which didn’t improve things. Other than that, I’ve not to put any fluid in the Master Cylinder reservoir. 

The Clutch Slave Cylinder is clean and dry inside. No sign of any issues or leaks. 

I’ve swapped over the Slave Cylinder to the other side of the bracket and, in the process, found that bracket stay back to the sump bolt is bent - I’m wondering if some previous incident has caused this to be damaged along with the bellhousing flange noted in my gearbox thread. 

From where the nut was on the engine side of the stay/bracket, I don’t believe I have enough straight/useable thread with the cylinder now on the other side - Does anyone have a stay they could spare? …happy to pay and cover postage.

Many thanks

Nick

[Drewmotty]

Inconsistent pedal travel without leakage is probably the little cup seal and it’s spring right at the back of the master cylinder. 
I’d fit a new seal kit which is cheap and easy. I like to use new old stock Girling seal kits. 

[iain]

Is the free play on the master cylinder correct? If not fluid can leak back and you end up with a variable effect.

[Drewmotty]

Good shout Iain. 

[Z320]

IMO the clutch master needs no free play

- the locking valve is already free play enough

- and even this is not needed, as long the master has free play

I know, at the workshop manual it is written different, but judge yourself: imagine this would be a bowden cable on a motorbike.

Does it need free play on the lever on the steering bar AND on the lever down on the gearbox?

Ciao, Marco

[iain]

28 minutes ago, Z320 said:

IMO the clutch master needs no free play

- the locking valve is already free play enough

- and even this is not needed, as long the master has free play

I know, at the workshop manual it is written different, but judge yourself: imagine this would be a bowden cable on a motorbike.

Does it need free play on the lever on the steering bar AND on the lever down on the gearbox?

Ciao, Marco

I’m not sure I understand Marco, but without the correct free play the clutch on my 3a won’t play ball.

[Z320]

1 hour ago, iain said:

I’m not sure I understand Marco, but without the correct free play the clutch on my 3a won’t play ball.

I'm not sure I understand you with this statement, please explain what happens.

[Z320]

Btw, a long and very positiv story with my clutch,

I ended with adding an external stop on my TR4A and an adjustable push rod instead the mushroom head rod.

This way I drive the car with the clutch master piston slightly pre-loaded (-> without play).

 

Because omy concentric slave is always in contact with the clutch cover spring the pre-load of the master is limited (-> locking valve slightly opened).

That works great!

Edited February 25 by Z320

[iain]

Marco “I think” what happens is as follows.

1. With full free play the low pressure zone of the cylinder is full of fluid,  in a sealed fixed volume.

2. The high pressure side is full of fluid, again a fixed volume.

3. As the rod is actuated the high pressure side volume is forced to the slave causing full activation if correctly adjusted.

However, if the free play is lost the fluid in the low pressure zone is not in a sealed compartment and allows escape back to the reservoir. As the low pressure zone also feeds the high pressure zone to maintain its volume under resting condition, this also looses ejected volume hence reduced activation of the slave cylinder.
 

An analogy is a heart with a leaking mitral valve, the  atrial ( low pressure)  chamber works as hard as it can to transfer blood the the ventricle ( high pressure) but the incompetent valve allows the fluid to leak back. 

As I said at the beginning “I think” this is what happens and certainly if on my car which is standard for all clutch fittings, if the free play is wrong gear engagement is poor to impossible.

[Z320]

Iain, which low and high pressure zone, please?

The pressure in a hydraulic system is the same everywhere (apart of the height of the system = zero on our cars)

Edited February 25 by Z320

[iain]

High pressure is the zone behind the plunger distributing fluid out to the slave cylinder.  Low is the other side of the seal allowing filling from the reservoir above. The reservoir side is never at high pressure. The discharge to slave cylinder is under high pressure when you press the clutch pedal.

Edited February 25 by iain

[TR4ffic]

Thanks for the posts, guys...

So... rightly or wrongly, I haven't had any 'free play' at the master cylinder - thinking that maximum effort/travel at the pedal and piston is best to get maximum out of the slave cylinder. I have 'free play' at the slave cylinder - so that the Release Bearing can come away from the operating fingers (?).

I have a TR2 WSM (Lockheed) with the TR3 supplement (Girling) but the supplement doesn't cover adjustment/'free play' at either the master or slave cylinders.

How should I set the system up correctly?

[TR4ffic]

Does anyone have a Slave Cylinder Bracket Stay they could let me have, please? …happy to pay and cover postage.

For something like this, I'd prefer to recycle than order a new one.

Many thanks

Nick

[RogerH]

Hi Nick

have you looked at VitesseSteve manuals  https://app.box.com/s/830280775a109252d69d

It may have more than your copy.

Roger

[BlueTR3A-5EKT]

Firstly, on a Girling hydraulic TR3-3A the factory did not fit pedal height adjustment stop screws in the master cylinder bracket.   Pedal height is adjusted by lengthening or shortening the master cylinder push rod.   Get it too far extended and the piston in the master cylinder will not release pressure when the pedal is fully ‘up’.  TR3 has different master cylinders to the TR4-4A that Marco has on his car, they originally had fixed length push rods, he has retro fitted back to adjustable push rod on one of his master cylinders and fine tuned the pedal height and free play to function.   The factory just fitted and trusted to design.   Marco has also got a concentric clutch slave cylinder fitted that comes from a modern vehicle, not the external cylinder originally fitted.   

Original TR3 & 4 Girling clutch hydraulics uses a return spring and adjustable push rod at the slave cylinder.  TR4 A does not.   It has a fixed length push rod and that design is to be self adjusting in service.   Same as TR250/5/6.    This is not relevant to the spring type clutch fitted in the TR2-4.  TR4A-6 had a diaphragm type clutch.   

Adjustment and set up to factory design for TR3-3A Girling hydraulics.

 Make sure you have pedal return springs fitted.

 Make sure both pedals move independently and freely.

Ensure all clevis pins and their holes are round and a good fit with each other. (5/16”)

Shorten or lengthen the master cylinder push rod to give some free travel and to set the pedals at your preferred height.   I set mine level and a bit above the throttle.

Adjust the slave push rod as per the service book instructions, and fit the return spring.  
 

PS I do not have a spare clutch slave bracket steady bar at all.

Edited February 25 by BlueTR3A-5EKT

[Z320]

Other TR owners sitting in my TR (and some driving it) are shocked how much better my TR's clutch works.

I can't be that much wrong with what I did, and specially not with the clutch pedal stop,

adjustable master push rod and slightly pre-load on the master cylinder (locking valve still open).

Try it on your TR and see 

Ciao, Marco

Edited February 25 by Z320

[Z320]

7 hours ago, TR4ffic said:

Thanks for the posts, guys...

So... rightly or wrongly, I haven't had any 'free play' at the master cylinder - thinking that maximum effort/travel at the pedal and piston is best to get maximum out of the slave cylinder. I have 'free play' at the slave cylinder - so that the Release Bearing can come away from the operating fingers (?).

+1

If it works, and if you are pleased, why do you want to change it?

[BlueTR3A-5EKT]

57 minutes ago, Z320 said:

Other TR owners sittig in my TR (and some driving it) are shocked how much better my TR's clutch works.

I can't be that much wrong with what I did, and specially not with the clutch pedal stop,

adjustable master push rod and slightly pre-load on the master cylinder (locking valve still open).

Try it on your TR and see 

Ciao, Marco

I followed your lead and reduced the master cylinder bore size.   Yes the ease of operation is a great benefit.  I went down from 3/4”(0.75”) to 5/8” (0.625”) Bore.    

Edited February 25 by BlueTR3A-5EKT

[RAHTR4]

Nick,

You have a P.M.

Regards, Richard

[TR4ffic]

17 hours ago, BlueTR3A-5EKT said:

Firstly, on a Girling hydraulic TR3-3A the factory did not fit pedal height adjustment stop screws in the master cylinder bracket.   Pedal height is adjusted by lengthening or shortening the master cylinder push rod.   Get it too far extended and the piston in the master cylinder will not release pressure when the pedal is fully ‘up’.  TR3 has different master cylinders to the TR4-4A that Marco has on his car, they originally had fixed length push rods, he has retro fitted back to adjustable push rod on one of his master cylinders and fine tuned the pedal height and free play to function.   The factory just fitted and trusted to design.   Marco has also got a concentric clutch slave cylinder fitted that comes from a modern vehicle, not the external cylinder originally fitted.   

Original TR3 & 4 Girling clutch hydraulics uses a return spring and adjustable push rod at the slave cylinder.  TR4 A does not.   It has a fixed length push rod and that design is to be self adjusting in service.   Same as TR250/5/6.    This is not relevant to the spring type clutch fitted in the TR2-4.  TR4A-6 had a diaphragm type clutch.   

Adjustment and set up to factory design for TR3-3A Girling hydraulics.

 Make sure you have pedal return springs fitted.

 Make sure both pedals move independently and freely.

Ensure all clevis pins and their holes are round and a good fit with each other. (5/16”)

Shorten or lengthen the master cylinder push rod to give some free travel and to set the pedals at your preferred height.   I set mine level and a bit above the throttle.

Adjust the slave push rod as per the service book instructions, and fit the return spring.  
 

PS I do not have a spare clutch slave bracket steady bar at all.

Many thanks for the feedback and detail, Peter.

Regarding clutch pedal height adjustment: As I'm tall (6' 3") I've needed to get the pedal further away from me (nearer the floor) so with previous comments about the low pressure side and filling the master cylinder from the reservoir, I'm wondering if I have too little travel on the master cylinder piston? I have the adjustable push rod at the master cylinder plus I've fitted stop screws to the bracket.

Cheers

Nick

[Ralph Whitaker]

Coming late to this thread but I don`t understand this business of "pre loading" the clutch master cylinder.  The small valve which is there to allow fluid into the system, such as when bleeding, is also designed to shut off as soon as the pedal is depressed so the fluid cannot escape back into the reservoir. So far so good. Unlike the brake system that needs to draw more fluid in as the brake pads and or brake shoes wear down, on a clutch system as the clutch plate wears the fingers or diaphragm moves out and pushes excess fluid back towards the master cylinder. If this excess fluid cannot return to the reservoir because the pre load on the plunger is holding the by pass valve closed surely you will get the same as a badly adjusted clutch where the pressure in the system cannot escape and therefore starts to hold the clutch partially released leading to eventual slipping.

Ralph

[rcreweread]

12 hours ago, BlueTR3A-5EKT said:

I followed your lead and reduced the master cylinder bore size.   Yes the ease of operation is a great benefit.  I went down from 3/4”(0.75”) to 5/8” (0.625”) Bore.    

If anyone is interested, I still have a couple of 5/8th" ( 0.625" bore) clutch master cylinders spare - all refurbished by Past Parts - Pm me if of interest 

Cheers Rich C-R

[Z320]

3 hours ago, Ralph Whitaker said:

Coming late to this thread but I don`t understand this business of "pre loading" the clutch master cylinder.  The small valve which is there to allow fluid into the system, such as when bleeding, is also designed to shut off as soon as the pedal is depressed so the fluid cannot escape back into the reservoir. So far so good. Unlike the brake system that needs to draw more fluid in as the brake pads and or brake shoes wear down, on a clutch system as the clutch plate wears the fingers or diaphragm moves out and pushes excess fluid back towards the master cylinder. If this excess fluid cannot return to the reservoir because the pre load on the plunger is holding the by pass valve closed surely you will get the same as a badly adjusted clutch where the pressure in the system cannot escape and therefore starts to hold the clutch partially released leading to eventual slipping.

Ralph

The clutch reservoir is good for filling and bleeding the system.

when the hydraulic works the locking valve could be locked - as long there is an adjustable play in the slave push rod.

My clutch hydraulics has no play in the slave CYLINDER:

this is why I can NOT FULLY pre load the locking valve; a gap must remain open.

The play is on a standard TR 3-6

- bearing of the pedal

- hole in pedal and and push rod fork, clivis pin

. mushroom head of the push rod hanging in the circut ring of the master

- gap mushroom head to the master piston

- piston travel to start locking the locking valve

- travel of the valve to lock

 

 

Edited February 26 by Z320