Clutch hydraulic problem

[piman]

Hello Broughworld,

are the supply pipe and bleed screw in the correct ports, the bleed screw should be in the top?

Alec

[broughworld]

Hi all, Thanks for the replies. I think the slave cylinder is the earlier type as it has the return spring on the outside of the cylinder body. I must admit I didn't make sure the cylinder was clamped in the retracted position before bleeding.

Also the hydraulic pipe enters at the top of the slave cylinder and the bleed nipple is on the bottom. Therefore I think I will have to make a new section of pipe so that it can be fitted into the bottom port with the bleed nipple being fitted onto the top.

I'll try your suggestions and see how I get on this weekend!

[ChrisDixon]

I need to bleed the clutch on mine, as I had to uncouple the flexible pipe in order to introduce a new heater pipe. I am curious about the comments on clamping the slave piston, as there is no mention of this in the factory workshop manual, which describes the usual 2 person bleeding process.

[piman]

Hello Chris,

my view about clamping the piston is that it is uneccessary, and cannot help.

Alec

[B87UL]

Broughworld

Your image of the slave cylinder appears to show the late hydrostatic cylinder with the earlier return spring. In addition, we do not know whether the clutch is the normal multi spring Borg and Beck or the later Diaphragm type. Added to this mix is that the slave cylinder rod changed four times at engine numbers 7B 5212, 7B 6571, 7B 10993 and another carried from 7B 10994 (3.4S numbers). A similar change happened to the adjuster assembly.

The arrangement shown in your image will cause clutch operation issues in any event, and if it ever worked would have clearance difficulties, or the pedal would pick up halfway up its travel, dependant on the push rod. Don’t in any case pump the clutch pedal to effect clutch clearance.These early hydrostatic operations had quite a few problems over a wide raft of vehicles and professionally I came across a few dozen types.

One of the early cars fitted with that hydraulic arrangement was the Mini, it was successful because it had a back stop to prevent the cylinder withdrawing too far. That is exactly what your arrangement requires in any event, a back stop, some would call it an adjuster. When set correctly it will allow setting of the clutch engagement position, clutch clearance and no over stroking of the hydraulics to damage the clutch.

If you look down this thread you will notice a few owners have experienced similar issues and of course extracting air will appear to cure some. However, they will still be left with a potential problem that the clutch just clears and expansion is liable to result in clutch drag. Trying to match the correct mix of parts seems to be all but impossible, some suppliers have tried to assemble kits but certainly the original pattern parts are not available for each scheme as detailed in my first paragraph. You will also find in most cases a further point affecting pedal pick up, is that many cars, at least S types, have been fitted with large bore master cylinders to lighten the clutch pedal. Even if the clutch slave had an original set of furniture the throw out volume from the enlarged master may upset the pedal pick up, but fitting a back stop can provide a workaround.

I will try to attach an image showing an experimental back-stop adjuster fitted to a S type with the early multi spring clutch. As the original rod for the earlier cylinder is not suitable for the late cylinder and some of the rods do not seem available it may be that a new rod needs making, or a later rod re-tapping further down the shank.

Owners may be quite satisfied with their clutch operation and the very varied mix of possible parts makes that a possibility but anyone experiencing a problem might consider the above points.

Clamping cylinders prior to bleeding was not an alternative in the late 50’s and early 60.s it was a necessity to obtain difficult clean bleeds, and mandatory on some vehicles. Clamping cylinders prevents pockets of air forming especially where the fluid passing through a cylinder is not inclined to draw the air.

In the Jaguar world, the Dunlop brake callipers benefit from clamping, so do early Rover P6’s and in fact Chieftain tanks with the same Dunlop gear. All brake assembles adjusted with snail cams follow a similar pattern from Ford to Rover. In the instance of clutch packs any with bleed screws at the opposite end to the piston usually benefit and nearly all hydrostatic operated cylinders. This does not mean you cannot bleed normally with success, it means it gives you an edge in difficult situations.

Later day mechanics have either forgotten or do not know the technique and most never worked on the vehicles at that period. The earlier problems in some brake and clutch designs were gradually overcome and the practice like many forgotten as skilled craftsmen retired. Present day mechanics are largely lead by the manuals, that was not the case in the 60’s, mechanics were expected to hold a Mechanics City & Guilds certificate at least and interpret with manuals that did not list the A to Z of problems. Many owners of classic cars struggle with issues that were solved 60 years ago and as the saying goes “If you don’t study the history you are bound to repeat it”