MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Bleeding clutch slave

usual problem - moving a centimetre but not enough to disengage clutch. No sign of air in the fluid - could this be the wrong slave (designed to move less ) or have I missed a trick in the bleeding process. Similar experiences of recent replacement slaves ?

No - this is not a first clutch slave change.
Roger Walker

Roger,you don't say how you bled the system. The clutch hydraulics are famous for hiding a pocket of air. I bled mine two weeks ago with ezibleed on 10 psi but g clamped the slave piston all the way back(still connected to clutch fork). Plenty more air came out. The clutch fork movement is now the best it has been.
C Harvey

Yes - good idea - I will try a clamp too
Roger Walker

I always bleed mine from the bottom up with the Eezibleed kit using very low pressure. The air is pushed upwards, the way it wants to go. Works first time every time.
Mike Howlett

Ditto Mike. But to avoid re-bleeding try wedging the pedal fully down overnight. The theory is that the pressure shakes air bubbles loose, which float up to the loop by the master overnight, then when you release the pedal next morning they are flushed back into the reservoir.

This works for brakes as well, but the front of the car needs to be raised as much as is practicable.

As far as the clutch goes if you have a lot of air it may need to be done a couple of times, but a centimetre now is almost there, as the normal travel can be as low as 3/8". If that doesn't work engage a gear before starting the engine with the pedal fully down, and test the biting point. If that is very low then either you have air, or the wrong ratio between master and slave. If the biting point is near normal then it is dragging for some reason.

Another cause of normal travel but low biting point is poor alignment between the release bearing and cover plate. This applies more pressure to one side of the cover plate than the other, so the side that moves less can still be engaged enough to spin the first-motion shaft and baulk in forward gears or grind in reverse. My roadster wrecked a graphite and a roller bearing (over many years it has to be said) as well as having a low biting point. It was only after having to replace the clutch a second time that I paid attention to this, and found it getting-on for 3/16" offset as in the attached (with the knackered roller bearing). I machined the arm one side and put a spacer washer in the other to bring it back in line.

If the travel and biting point are normal but it still baulks and grinds, then that can be caused by a binding pilot bearing through dirt/lack of lubrication, or a slightly bent first-motion shaft.



paulh4

Mike, I usually do it bottom up but not with the eezybleed and this time I couldnt find the pump. Interesting post Paul; yes, it was nearly there at 1cm travel but following CH's advice I climbed underneath with a clamp but first thought I would see if I could simply push the lever as far into the cylinder as possible - there was a little movement and presto ! bubbles ! and all is now as it should be. Interesting advice about leaving the pedal depressed overnight - I shall file that away - the A needs bleeding this winter.

Thanks everyone !
Roger Walker

Glad you came right.
Craig
C Harvey

"I usually do it bottom up but not with the eezybleed"

For those that don't have an EeziBleed the other bottom-up way is to link the offside caliper and clutch slave nipples with a length of tubing - they are the same size.

Two people are needed - open the clutch slave, pedal person applies light pressure to the brake pedal, open the caliper slave. The pedal goes down and when it reaches the bottom the caliper nipple is tightened before the pedal is released, and the process repeated.

Needs space in the clutch slave of course, and if empty to start with refill it this way as well, but only until you can see fluid above the cylinder at the bottom of the reservoir, then top-off both masters as normal. It only takes two or three pumps, but of course keep an eye on the brake master level while you are doing it.
paulh4

Paul
Your method sounds like simplicity itself. Makes a lot of sense.
Rod
R J Pemberton

This thread was discussed between 19/09/2017 and 23/09/2017

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now