Introduction #
A Clutch Slave Cylinder will eventually fail. You have the option to do a simple rebuild, for which the kit contains just 2 rubber parts. Alternatively, you may choose to just replace the clutch slave cylinder. After market units are available and are not very expensive. It really depends on the condition of the clutch slave cylinder, and specifically the condition of the bore. A rebuild can make sense if the unit is in generally good condition and the bore it clean. Unfortunately, you can’t know this until you take it apart.
Background #
The Clutch Slave Cylinder is the piece that uses hydraulic pressure to move the push rod. The push rod only moves 3/8th to 1/2 inch but this is enough to operate the clutch lever. This is inside the gearbox bell housing and the lever has the release bearing attached. This movement of the release bearing releases the clutch when pressing in on the clutch plate. Brake fluid sits behind a rubber fitting that moves in the bore of the clutch slave cylinder moving the piston. This rubber fitting wears and starts to allow fluid past it and the piston. If you inspect the clutch slave cylinder and you can feel or hear fluid in behind the rubber dust cover, the rubber fitting is leaking.
Removal #
The Clutch Slave Cylinder attaches to the gearbox by two bolts – use a 9/16ths socket. Then remove the push rod from the dust over of the clutch slave. It will then hang by it’s rubber hose connection if needed. You should be ready to cap or plug the hydraulics to prevent the clutch master cylinder from draining. You can remove the rubber hose from the slave cylinder, which is pretty easy. Do not loose the copper washer. Then plug the end of the rubber hose. Vacuum line caps work well for this and are available locally if needed. Amazon is also a source.
You should also take the time to inspect the rubber hose. If you do not know the age of the hose, or it shows any signs of wear, then replacing it should be planned. This does make the job longer and a bit more complex. Removing the rubber hose and hard line connection is unlikely to be described as fun. That is detail and scope for a separate knowledge base item.
Inspection #
You can now begin your inspection of the slave cylinder. Remove the retaining ring around the rubber dust cover by prying it off. Then remove the dust cover, as shown above.
You should now be able to see the piston and it may protrude a bit from the body so that you can grab it and pull it out. Do not use pliers or anything on the piston, its a machined smooth surface. If it not protruding you can try carefully blowing into the hose connection on the body or using some compressed air.
Behind the piston is the rubber fitting and a spring. You will also need to remove these. They should come out relatively easily. Again just don’t do anything to remove them that might scratch the bore of the slave cylinder body.
Now you can take a look at the bore inside the slave cylinder body and the piston. If there are score marks of other damage you will want to replace the entire slave cylinder. If it can be cleaned up, then the rebuild kit should work just fine.
Cleaning #
Now you can proceed to get everything super clean. Use shop towel and your favorite cleaners to clean up the body, the bore and the piston. Once clean check the piston moves freely in the bore of the slave cylinder body. If necessary, use some very fine (400 or higher) grit sandpaper to smooth off any rough parts.
Reassemble #
You can then finalize the rebuild by reassembling everything. Insert the spring, and then insert the new rubber fitting from the rebuild kit. The solid/flat side should be facing outwards to mate with the piston. The concave side sits on top of the spring on it’s white plastic top. Then install the piston, don’t push it all the way in. Lastly install the dust cover and the securing ring. The new dust cover is the other rubber part that comes in a rebuild kit.
You can then reinstall the clutch slave cylinder and you will need to bleed the system. Although not covered in full here, I like to slowly and carefully fill the slave cylinder with brake fluid. Then attached the rubber hose, with copper washer. Let this hang down overnight and very little bleeding, if any, will be needed.
Replacement Clutch Slave Cylinder #
These are available from the usual online MG parts vendors. Full kits are also available on Amazon.
Nearly universally, when you buy new, note that the bleeder screw is always in the wrong place. For packaging purposes the bleeder is inserted into the fitting where the rubber hose connects. You need to remove the bleed screw and put into the correct place. Typically you will find a plug in the hole where the bleed screw needs to go.
It is critical that you get the bleed screw into the correct position. If you do not, then you will never be able to fully bleed the system and get all of the air out.
Other Materials #
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