MG Car Repair: MGTF master brake cyl

Question
Hi Barrie , I have a brake problem with 1954 MGTF . I need to pump brakes at least once to stop.  I replaced shoes, rebuilt, wheel cyl. bled system several times. There was lots of rust in the master cyl. when I bought the car . I suspect the master cyl seals are shot. Bought a mcyl from Abington. It arrived today.  Question: how do I get old one out and new one in ?  Body is on and there is a 6in by 12 in window in floor over the mcyl . Not sure how to even reach bolts. New mcly came with a new boot but no rod. Please help.   thankyou.  Trip

Answer
Hi Trip.  The master cylinder is accessed from underneath the car.  It is held in place with two bolts.  First undo the hydraulic pipe and gently move it out of the way.  Next undo the two nuts and extract the two bolts.  The master cylinder can now be pulled out of the pedal box complete with the old boot, leaving the push rod behind.  

Clean everything and then fit the new master cylinder.  Remove the plate on the side of the pedal box to gain access to the master cylinder push rod.  Check the clevis pin - they do wear badly.  The push rod may need to be adjusted to give about 3/4 of an inch free play at the pedal.  

If you intend to use DOT5 silicone brake fluid then get back to me for additional advice before fitting, because you may need to modify the master cylinder slightly before fitting it.