Discovery clutch

[Slick74]

Hi fitted a second hand gearbox to sons disco 1 today and whilst at it renewed the clutch, Borg and Beck, built it all up and no pedal, bled off even though never touched hydraulic side, but can only get half pedal, suspect can't be clutch or bearing, fork etc as it does drive, before I try back bleeding tomorrow has anyone get any other suggestions? TIA

[sierrafery]

If you are sure you didnt fit the flywheel the other way around cos that's very common, you should replace the slave cylinder first cos once removed from the box it's seal got hurt by the edge of the internal wear as you released the pressure from the rod but the good practice is to replace the master too as it may fail in short time being stressed by the new slave's higher backpressure, I was stubborn enough to longitudinaly cut the slave cylinder which i removed from mine but dumb enough to not take pics of it , the gist is that the piston seal creates a wear in the cylinder's body along it's travel which at the end remains as new so a small edge there, as the cylinder is removed from the box and the rod released the pressure from the pipe pushes the piston a bit forward and when the seal meets that edge it gets hurt/bent then it becomes impossible to be bled well, even if after a long ''fight'' will seem OK it will not be as new whatsoever, it's not so expensive so IMO if it's old better put a new one and will not take more than 10 pedals with funnel attached to be nice and hard... did it several times and always worked a treat

if you replace the slave before you bleed the clutch you must be sure that the line was filled all the way so first of all direct the pipe into a bottle and keep filling the tank(without touchung the pedal) untill a clean flow comes out there, move with talent and attach the cylinder fast, then open the bleed nipple untill fluid comes out there too and only then follow that bleed procedure with pedals and funnel attached... back bleeding the clutch is a nonsense IMO it will work only if there's little air trapped in the master cylinder or upper side of the line not along the circuit or slave side of it

use the ''official'' method just make the improvisation as in the pic, fill the ''device'' before you connect it to the bleed nipple, keep it abobe it and be patient with pedal depressed untill all the bubbles are leaving the ''funnel'', max 10 pedals and it will be perfect,

you can stick the pedal to the floor with something and let it so overnight, this used to help too provided the cylinder seals are OK

[Snagger]

The story about needing to replace both clutch cylinders together has a little bit of mechanical basis, but only as far as that if one is worn, then the other probably is too. Other than that, it's myth. There is certainly no difference in pressures from replace a cylinder - the master applies pressure and the slave moves in response. The pressure experienced inside the system is dependent on the spring pressure of the clutch pressure plate resisting the slave movement, given that the diaphragm springs are the item the hydraulic pressure is trying to move. You will only change the hydraulic pressure in the system if you have a stiffer pressure plate or a seized plate or fork.

I have often had half pedal issues with LRs, and it has always been trapped air. The one stage missing from the bleeding instructions in all the manuals is to make sure the nose of the car is higher than the tail, so that any air in the slave cylinder rests against the inside of the bleed nipple, not the back of its piston where bleeding will fail to shift it.

[Slick74]

Hi thanks for the reply, after trying to bleed again this morning we replaced the slave cylinder and managed to bleed it up, I will look into renewing both the slave and master cylinder

[sierrafery]

There is certainly no difference in pressures from replace a cylinder - the master applies pressure and the slave moves in response.

we can agree that we disagree on that ... take a new syringe and absorb/push water with it 100 times and you'll see that the more you'll work it the the easyer the piston will move...that's what happens within the cylinders too so a new slave will put bigger stress on the master than the worn one as the piston moves harder and that usually kills old seals ... and if they both are the same age the master will fail soon as well so why bleed the system twice that's all i was trying to say

[Snagger]

The amount of friction in a healthy cylinder is negligible compared to the resistance from the pressure plate. If you have a failing second cylinder, and age can be a factor, it makes sense to replace it at the same time, but replacing one cylinder has absolutely no ill-effect on the other; in fact, it'll help the other as you should be replacing the fluid at the end of the job with clean fresh stuff, not contaminated and mildly abrasive old fluid. I have worked that way for twenty yeas with several LRs, and have never had a cylinder fail within several years of replacing the other. Honestly, it is a myth put about by salespeople.