Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Replacing Brake master cylinder - easy ??

I was wondering if Peplacing Brake master cylinder in a B GT was an easy DIY job and if can someone give some step by step guide ?

much appreciated !

Not too difficult, depending on the size of your hands! You need to get the pedal box cover off (the screw alongside the inner wing will need a magnetic screwdriver for replacement if not removal), and remove the large rubber plug that is behind the master cylinders. These should allow you to get to the hydraulic union as well as the mounting nuts and bolts, although as I recall the latter is still a fiddle only being able to tighten the bottom one one flat at a time, or possibly only 1/2 a flat turning the spanner over each time. Hence slim hands being able to get in and spin the nut off and back on as far as it will go once it is loose. I've heard much tell of 'bench bleeding', never done it, never needed to, sounds a messy business to me. The new master should have a plastic plug pushed into the hydraulic outlet, leave this in place until you have it mounted and are ready to attach the pipe, likewise *slacken* the pipe union while the mounting bolts are still fitted, but only fully remove it when you are ready to remove the master from the car. Cover the pipe union with a clean bag or cloth until the last moment before refitting. Fill the new master with new fluid, then a gunson's EeziBleed will be much easier for flushing the old fluid out of all the pipes than pumping the pedal. Flush out the shortest pipe run first, to the longest, closing each bleed nipple before moving onto the next. When bleeding start with the longest run (i.e. left rear) and work towards the shortest. Even when all that is done I find I still have to have someone stand on the pedal while I rapidly open and shut each caliper nipple to get the last bit of air out, or the first pump of the pedal is long.
Paul Hunt 2

Jon - You can make installation of hte new M/C much easier if you will install (or have a machine shop install) 5/16 - 24 (UNF) Helicoils or Recoils in the mounting holes in the mounting flange of the M/C. This eliminates the need to put nuts on the bolts when installing the M/C, You can just use a 6" extension with a 1/2" socket to get the bolts started from under the dash. Cheers - Dave
David DuBois

I just pulled mine today. Took about 15 minutes to get it out, but I'm not sure if later models are any harder (mine is a Mark I). Re-installation is just as easy, but you will need to bleed the brakes when done. The early units can even be changed without going in from the cockpit.

Unless you use silicon brake fluid, beware of the fluid leaking onto your paintwork. It will eat away the paint in no time and rust like crazy.
Steve Simmons

This thread was discussed between 20/11/2006 and 21/11/2006

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.