Clutch Master and Slave Cylinders

[richard btype]

The clutch slave cylinder's swollen rubber and rusty case looked close to leaving me stranded although the system worked without fault but as preventive action managed to find and fit a new/old stock jaguar item.

A complete bugger to fit but since then have found the need to pump up the pedal to ensure a clean gear change. So with a couple of bleeding sessions later and a double check on the rod adjustment the pedal still bites too late whereas a pump up does the job and a visual check under the car one can see the rod travels half a crucial inch longer after pumping.

I may have a faulty slave cylinder of course but one tends to trust and there is no sign of fluid leakage from it!!! could fluid by pass the rubbers but yet not leak?

So it was off with the master cylinder and a repair kit from SNG, the unit is the original one with an aluminium tag showing its build date from 1962. After a strip down and good clean there was rust at the start of the bore for approx half inch but deeper in the bore in the working zone it was clean but with the finger could feel an unevenness but of importance there was no sign of leakage.

The flexible pipe also appears to be in good condition and probably not that old but I guess could have broken down inside allowing expansion - again no sign of leakage and the fluid level remains constant in the reservoir all joints are dry

After rebuilding the MC and refitting also a difficult job returning the clevis pin! there is no improvement.

My next thought is to have the master cylinder sent away and resleeved with stainless so the original rubbers can be used and the original MC retained as the uneven bore wear needs addressing regardless.

So there is no answer to why full pressure is not available but as a starter can anyone recommend a company to resleeve the MC and I'll probably do the Slave while at it? or am i missing something here?

Just to be clear, there is always pressure but just not enough unless pumped to enable a full clutch release.

Any thoughts appreciated...

Richard

[Heuer]

Are you sure you have the correct slave cylinder actuating rod? The one for the 80mm slave and the 95mm hydrostatic slave are different lengths: C9798 for the 80mm slave, C24148 for the 95mm slave. Also if you fit the hydrostatic slave and use the non-hydrostatic return spring you get the effect you describe.

[christopher storey]

Richard : the usual cure for this particularly puzzling symptom is to lengthen the actuating rod on the slave . In one case I had to weld a short extra length of rod onto the original - merely screwing it out to its ultimate length did not do the trick

As David has said, there may be a mismatch of parts which is causing or aggravating the situation

[PeterCrespin]

Sounds like more bleeding is needed if it works fine after a second stroke.

Pete

[44DHR]

Richard,

The answer to your original question as to who can re-sleeve you brake parts in stainless - is Past Parts in Bury St Edmonds. They advertise in the Classic Car mags and offer a very good service.

Just Google them to see their website or click http://www.pastparts.co.uk/

I have no allegiance to them - just a very satisfied customer.

regards,

Dave
1967 Series 1 4.2 FHC

[christopher storey]

Peter : you can bleed till you're blue ( or should that be white ) in the face and it will not cure this problem , because it is not caused by air in the system, even though it feels that way. The pedal comes up solid and you think all is well, and a few minutes later the pedal can be pushed down with one finger. The problem results from a mismatch of the stroke of the master cylinder piston and that of the clutch cylinder piston during the phase where the pedal is released . The key to its solution seems to be to lengthen the actuating rod on the slave so that the slave's piston is pushed back to its furthest limit . It then starts to move ( and thereby actuate the release lever ) almost as soon as the master cylinder piston is moved

And, as David has said, mixing and (mis) matching of parts does not help!

[PeterCrespin]

Peter : you can bleed till you're blue ( or should that be white ) in the face and it will not cure this problem , because it is not caused by air in the system, even though it feels that way. The pedal comes up solid and you think all is well, and a few minutes later the pedal can be pushed down with one finger. The problem results from a mismatch of the stroke of the master cylinder piston and that of the clutch cylinder piston during the phase where the pedal is released . The key to its solution seems to be to lengthen the actuating rod on the slave so that the slave's piston is pushed back to its furthest limit . It then starts to move ( and thereby actuate the release lever ) almost as soon as the master cylinder piston is moved

And, as David has said, mixing and (mis) matching of parts does not help!

The way you describe the symptoms Chris, I certainly accept it doesn't sound like a normal bleeding issue . Thankfully it's not a bleedin' normal issue either...

Pete

[richard btype]

Thanks to each for the responses.

The rod lengthening is something I had not considered but somehow might work. The positions of the piston in the MC and original slave respectively and the MC with the new slave respectively might vary....

The slaves I should have mentioned are both the same in dimension i.e. 70mm? the shorter of the two available. I also had to fit a new return spring as the original was too fatigued but was a good match for length.

[Heuer]

Did you measure the actuating rod? There are two sizes - 3.5" and 3 7/8" IIRC