Problem bleeding the clutch hydraulic system

[Cyder]

So to set the scene, I have a MK1 on which the clutch bite point would move down the pedal when held in gear until the clutch engaged.

As there was no fluid loss I concluded that it had to be the master cylinder seals failing.

So at the weekend I went and picked up a replacement master cylinder that had just been taken off a breaker that same morning so I know the bugger works correctly.

I installed it yesterday and filled with fluid but here's where the fun begins...

I just can't seem to get it to bleed. I've tried the old fashioned method of getting the missus to sit in the driver seat and pump the pedal repeatedly before holding it down and then cracking off the bleed nipple to release the air but nothing seems to flow out in any great volume and the level of the master cylinder isn't changing.

Any ideas? Does the master cylinder need any kind of 'pre-bleeding' or anything to get some fluid in the system?

[howlinmadmartin]

sometimes the master cylinders do need bleeding try just cracking the pipe like a bleed nipple when your missus presses the pedal down then lock off etc etc, do this until you get fluid bleeding out then try bleeding as normal. This has worked for me on new stuff but ive never fitted second hand so dont know!!

[Cyder]

Interesting thanks, disconnected the master cylinder from the system earlier and pumped the pedal a few times and no fluid came out so I think I'm going to need to bench bleed it before refitting.

I'm getting bloody good and climbing around in the footwell now. Good job I'm only a small chap at 6ft 2 and 19 stone.

[MG CHRIS]

Also try adjusting the rod on the pedal to master cylinder if its not adjusted correctly it will not allow the fluid to pass through the pipes. I did see a guide somewhere on what the correct gap should be.

[Oldandslow]

Hmm. I did this a while ago. Not a new master but the system was empty after the seals on the slave went. Same way I do brakes.

Put a piece of tube on the nipple dipped into a jar of fluid making a non return. With the nipple open, fill the reservoir and leave it for a wee bit to let it drain in if it can. Then gentle pumping of the pedal, bubbles of air coming out of the tube end dipped in the jar. Keep going until the air stops and it's only fluid coming out in the tube on the nipple. Seal the nipple.

Just to add suction systems are available for not very much which are supposed to be the mutts nuts for bleeding but I've not tried one.

Edited by Oldandslow on Tuesday 3rd June 02:32