QuestionQUESTION: My master cylinder went on my 1974 mgb. In order to remove it I had to drop the brake and clutch pedals and remove the slave clutch master cylinder(what a pain in the butt). I am about to start the re-install any tips on installing the master cylinder and bleeding the brakes/clutch cylinder
ANSWER: Hi Neil. Removing a master cylinder can be a pain. In particular, if you have a USA specification car, then access to the bottom bolt may be difficult, depending on the year. You may need a helper. I quote some paragraphs from my workshop manual:
o USA and Canada only: Remove the fascia lower panel.
o Remove the access plug from the bulkhead.
o Unscrew the bolts and nuts, noting that access to the lower bolt is gained from inside the car through the access hole in the bulkhead.
o On re-assembly, the lower bolt goes in with the nut facing rearwards, but the upper bolt goes in the other way round.
When bleeding the brakes, I use a Gunson’s speed bleeding kit. This is a plastic bottle with two tubes attached to it. You pour a can of DOT4 brake fluid into it, connect one tube to the top of the master cylinder with the adapter that comes in the kit, and connect the other tube to the valve on your spare wheel. Then you just go round the car opening each bleed screw and waiting until no more air bubbles come out.
There is a trick with the clutch cylinder. Before you bolt the slave cylinder to the transmission, just let it hang vertically on its flexible hose. Push the piston up into the cylinder with a Philips screwdriver (or your thumb) to expel any air upwards. This works much better than using the bleed screw. Make sure the master cylinders are both topped up to the correct level afterwards.
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QUESTION: The brakes are done but I no matter what I try I can not get the clutch cylinder to bleed. HELP
ANSWER: Hi Neil. I cannot understand why you are having so much difficulty bleeding the clutch. What exactly are the symptoms? It might not be a hydraulic problem.
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QUESTION: The clucth pedal is very soft, will not firm up. Is not the same as before I removed it
AnswerHi Neil. It sounds hydraulic. On a LHD car the metal pipe from the slave cylinder to the master cylinder goes across the bulkhead just below the heater unit. This pipe must be level. If any part of it bends downwards then it will trap an air bubble. You need to dislodge the air bubble so that it exits the pipe upwards into the master cylinder.
If possible, straighten the tube. You can also jack the car up on the driver's side so as to tip this pipe upwards. This action alone is sometimes enough to release the air bubble.
If that doesn't work, then with the drivers side of the car car jacked up and securely held up on axle stands, remove the slave cylinder from the bellhousing, let it hang vertically from the flexible hose, and then ram the piston inside it upwards as fast as you can. Do this several times, waiting 30 seconds between operations. If you have a helper, get them to look inside the top of the master cylinder and tell you when a bubble appears.
