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MG Midget and Sprite Technical - Bleeding clutch slave cylinder!

I am about to search the archives, but thought you may be able to help quicker than I can get the information from the archives.
I have just changed my slave cylinder (1275, 1971, mk3, ribcase, 4 speed) and flexi pipe and I am now struggling to get fluid out of the bleed nipple.
I have tried the pump the pedal method and easibleed pressurised method, but nothing.
Any tips?
I am now thinking I didn't undo the nipple enough. I will have another go and undo the bleed nipple a good couple of turns.
Dave Brown

How old is the master cylinder or it's seals? They have a habit of going together. i.e. remove fluid from the system to replace slave cylinder or it's seals allows old MC seals to relax enough to not seal properly when subsequently bled.

Or you just haven't opened the bleed nipple enough!!!!!

Rob aka MG Moneypit

It is always a pain in the ass..... I start with priming the master cylinder and wait for half an hour. Than I place the front of the car higher than the back to get the bleeding-nipple in the highest position. If I am not successful with that: I remove the slave withe the pipe on the slave and start pumping. If there are no bubbles anymore I rebuild slave with the 2 bolts . (witch I made shorter).

Flip Brühl

Push the slave rod fully INTO the slave cylinder and get something to hold it there. Then have a go.
Lawrence Slater

Precisely. Wire it up. But use the eazibleed, not the pedal, I would suggest.
Nick and Cherry Scoop

I like 'Easibleed' too. When I bought my midget the clutch worked fine, if a tad notchy. But when I took my slave and master cylinders apart, to renew the seals and hone the bores, they were both full of rusty, gooey gunge; as was the flexi-pipe. If the system is clean it should bleed really easily so I suspect it's time to clean out the master and the pipe. Though the slave cylinder is new on your car, it might be that the gunge has made it's way to it so it might be advisable to take it apart and clean it too. BTW, when clean, the bleed nipple should seal fully using only finger-tightness so you only need the spanner to nip it up half a turn to stop it undoing. If it's not sealing easily there's dirt in the system. I've also changed to silicone fluid so I don't have to worry about the paint.
Nick Nakorn

I knew things weren't quite right. I inspected the eezi bleed and found the pipe from the bottle to the master cylinder was blocked. Cleaned it out and it bled OK. There is still a little air in it, the clutch bites very low, but I will have another go tomorrow to get the last of it out.
I think I will wire the pushrod in to the slave cylinder too.
Thanks for the help.
Dave Brown

I used a wide throat welding clamp to hold the piston inside the slave. A bit fiddly but it enabled me to get two bubbles out after previously trying for hours. 2 bubbles, and small ones at that, were the difference between clean gearchanges and crunchy ones.

Rob aka MG Moneypit

Hi Rob,
I used a long G clamp to hold the piston in the cylinder and got more air out. It still didn't bleed 100%. I did push the fluid up to the master cylinder though. I then left it a couple of weeks while I went on holiday.
Yesterday, I had another go but this time I attached the tube to the slave and opened the bleed nipple and then pushed the slave piston in to the cylinder. A large bubble of air came out (about an inch long). Then I bled the system again and no more air came out. I am hoping that is it. The pedal feels better but there now looks like there is play in the pedal clevis pin - another job for later.
I didn't have time to test drive yesterday as I changed the gearbox oil, diff oil (mobile synthetic as recommended by Nigel) and the prop shaft too (the replacement being recently reconditioned and balanced by Reco Prop) and ran out of time.


Dave Brown

I use a Motive power bleeder connected to a lockheed cap drilled to receive the hose fitting. Works great on all my cars' brakes, too, using different fittings they sell. This is their website, but you can get them on Amazon, et al:

The best method I've found for the clutch slave is to bleed the system with the slave uninstalled and held above the master. I then install the slave, and subsequent flushing is done easily with the slave in place once the air is evacuated the first time around.

I have a Rivergate aluminum billet slave, though, so I guess this isn't feasible with the original system, as the OEM hose fittings might have to be assembled through a mounting tab, if memory serves. However, perhaps a truncated 'lift' is still doable, as Flip suggests. Tapping the line and slave with a screwdriver handle seems to move larger bubbles along the circuit, too.

These cheerful blokes have a video tutorial using an easy-bleed, with the slave in place: Looks far too easy.

JM Young

I drilled a small hole in the reservoir cap and inserted a air needle (used for pumping up basketballs, etc), connect a hand pump and have someone slowly push down on pump handle as yo work bleeder on slave. Epoxy the hole. Last time I did it, found the lid on the bottle of fluid fit the reservoir so I didn't have to re drill hole.
Kth Hurt

My method is as follows.
Connect a 2 metre long piece of clear pipe to the bleed nipple. Put the other end in the master cylinder reservoir ensuring that some of it is visible when sitting in the drivers seat.
Put the radio on.
Undo the bleed nipple.
Sit in the car a start slowly pumping the pedal.
You can then watch as the bubbles come through the tube. Keep pumping until you don't see any more bubbles. This can take some time, hence the radio.
Close the bleed nipple and remove the pipe (without dripping fluid on the paint work).
Cheers Tim
T Dafforn

This thread was discussed between 24/08/2014 and 17/09/2014

MG Midget and Sprite Technical index

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