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MG Midget and Sprite Technical - Clutch slave cylinder

I've just put the engine back in my 1275 midget its been off the road for about 2 years. Connected up the clutch hydraulics and the pedal has no resistance. I have removed both Master and slave cylinders.

The slave cyclinder on inspection has a small (2mmx2mm) rough section about 30mm into bore. Does this mean I need to by a new slave cylinder, don't want to spend more money if it can be avoided.

No evidence in either master or slave of what caused the problem. Should I be able to see a damaged sealing ring. Intersetingly some of the drained fluid was completely black and the slave cylinder had small very thin "bits" of black stuff.

thanks in advance

Tim
T Wainwright

Tim,
Congratulations on getting your engine back in - that's progress!

As you are probably aware the clutches are notoriously difficult to bleed correctly, so starting with a corroded / damaged slave cylinder is really going to g0ve you an uphill struggle.

The black fluid and bits probably indicate that the piston rubber seals have disintegrated. You might be able to hone the bore to get rid of the corrosion and then fit new seals but from your description I really think you will need a new slave cylinder.

Guy
Guy Weller

Tim. As Guy says, it sounds like your slave cylinder is goosed, so when you get a new one, which really is the best way round the problem, also get yourself an "Eezibleed". They are worth their weight for one man brake bleeding and in particular the clutch on Spridgets.
When you bleed the clutch, disconnect the slave cylinder from the clutch fork and push the piston all the way in and secure it there with a piece of welding wire or something. Only by doing this will you get all the air out, re-connect and Bob's your uncle. (acknowledgement to Bill SDGPM)

Bernie.
b higginson

What colour is the fluid in the master cylinder reservoir, usually if a seal has started breaking up it is best to replace both

Sometimes a simple seal swap will do but for the cost of a slave cylinder I'd do seals in the master and new slave at t'other end

And check the flexi hoses too its not easy to tell if they are cracking inside but it can happen and give problems later.

Then you need to completely replace the fluid anyway, which it sounds as if you'd need to if there's contamination


"(acknowledgement to Bill SDGPM)"

not sure if it was me suggested that, possibly not but it's good advice too
bill sdgpm

Thanks for the advice.

The bore in the slave is good except for the one location which is not so much rust as a very shallow indentation. £21 new slave added to shopping list.

I cant see any damage to the master so perhaps I can get by with a seal kit. £50 saved

other items

steel clutch line (due to damaged hex heads)
flexible line (holes everywhere)
new slave push rod (original very oval)

I made a bit of an error when I replaced the engine I forgot to replace the bush in the release fork. For the sake of a 99p item I may have the engine out again. I think I'm going take a chance and connect everything up. I cant face pulling the engine again. Is there a way to check this from under the car. Lots of side play but tight in the direction of movement front to back.

I'm sold on the idea of an eezibleed. I attached a garden sprayer to the brake res cap last time I bled the brakes, worked a treat.
T Wainwright

Pushing the slave cylinder piston as far back as it will go is something that I have done for years, and suggested here often before now. But there is certainly no monolpoly on good ideas and one of the best things about the BBS is how ideas like this often come from multiple sources and quickly get adopted by others.

The reason this works is that the bleed nipple and the input pipe are right next to each other so if the piston is at the other end of the bore it is possible for air bubbles to remain lurking in the cylinder, whilst fresh fluid is pumped in the supply pipe and straight out of the adjacent bleed nipple.

If the fluid in the M/C is clean, I would be inclined to leave well alone there and not even replace the M/C seals. You can always come back to that later if necessary. I would keep topping up the reservoir and bleeding it through until the system was fully charged with fresh fluid. I always thought it would be good if brake & clutch fluid was available in two or three colours - then you could choose a new colour and pump that through until the colour changed at the further-most bleed nipple and you could then be certain that you had done a full fluid change.

Guy
Guy Weller

I've pushed on and stripped everything out. MC bore looks OK so I will just replace the seals. Fluid in master cylinder was very black.

T Wainwright

This is what the slave cylinder bore looks like apart from one small area its unblemished.


T Wainwright

At £21 for a replacement and nearly half of that for just a set of seals it isn't really worth messing with. But that said, you could probably get away with lightly "honing" that with 1200 wet & dry.

Guy
Guy Weller

As Guy says it isnt really worth messing about, but it's your cash :)

The black fluid in the master means that the rubber deterioration is likely to have started there, so new seals at least is sensible.

Lots of longitudinal lines down inside the slave indicate that honing, at the very least will be needed to prevent a sooner than later cylinder replacement.


As Guy suggests, very fine wet'n'dry could be used (rotate on a piece of dowelling in a drill, with brake fluid as lube) to take out the lines

Proper honing is really advised and frankly with the amount of marks and the blackened fluid I would just buy new.

Ebay CAN be your friend here, it isn't only full of chancers (even though there are enough of those in there) you can get parts needed at less than dealer's prices

And before you buy, check out the dealer's prices first

Sometimes...
bill sdgpm


I have a very similar problem & know from experience how difficult it is to bleed the slave.

It also looks a pig to remove the slave because the 2 bolts are close up to the subframe. So, it's off to my friendly classic car specialist on Friday week week. I have also asked for the flexible hose to be replaced at the same time for good measure.

Whilst there I have asked for a mod - which apparently is fairly common. Using an extra flexible hose bung one end in to where the bleed screw should go & feed up to a suitable point in the engine bay (the heater box area seems favorite). Add a coupling & then the bleed screw to this higher end & no more skinned fingers.

Tim - you may wish to consider this.

Gavin Rowles

Gavin means like this

maybe


bill sdgpm

Gavin,

I like the idea of a new pipe run from the bleed hole to a new more accessable location. Even if this took it just to the underside of the cylinder.

Do I need to the pipe and connectors made up by a garage or is there a diy option. (ever relucant to part with the folding stuff)
tm wainwright

I knew I had a picture of the upper end of that

HTH


bill sdgpm

just normal brake pipe, 3/16 UNF male ends on mine, just long enough to run from slave to bell housing upper and a double female connector BCA4002 to make the connection

The 3/16 UNF fits the slave exactly the standard bleed nipple fits the connector exactly too and has a tapered inner hole which allows the nipple to work correctly

A small bracket to hold it at the top of the bell housing finishes the job

I did an alteration to my previous post but it vanished
:(
bill sdgpm

alternatively Peter May does a nice kit in stainless braided hose for twenty-something quid.
David Smith

Bill you're not supposed to paint the spark plugs as well you know....
Tarquin

My "remote" bleed nipple is as Bill's - i.e. a cupro-nickle pipe, but I believe that a standard single flexible rear brake hose can also be used and is the correct length to reach up alongside the rear of the block where it is accessible from inside the engine compartment.

Other easy modifications worth doing whilst you are at it is to: a) shorten the two UNC bolts that hold the slave in position - as standard they are longer than necessary and shortening makes fitting and removal much quicker. b) grind a cone- point to the end of these bolts to make it easier to start the thread and c) it is also possible to slot one of the two bolt holes in the slave cylinder which means that the bolt only needs to be slackened off a little, rather than being undone completely when removing the slave cylinder. All worthwhile modifications that make a tricky job very much easier.

Guy
Guy Weller

Invest in an Easibleed and then fit it back to front - ie attach it to the slave cylinder screw open it and then very slowly crack the union at the master cylinder - use lots of rags to catch any fluid. Once fluid starts to appear tighten union and bleed screw - always works for me. I do like the extended pipe from the slave cylinder though.
Either way no matter how long you try to bleed it conventionally you will never get rid of the air lock in the high pipe from master to slave cylinder.
I wouldn't rush to change the cylinder just yet it looks fine.
Andrew Dunn

er Matt

are you sure?

I read something somewhere



'twas inna book

could have been a green one

or...
bill sdgpm

This thread was discussed between 09/05/2010 and 10/05/2010

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