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MG MGB Technical - Brake M/C rebuildb

Rebuilding a '77 B brake master cylinder. How do I remove the pressure differential piston assy. ? Bently manual p. 210 #17. says, "Apply air pressure to the primary outlet port." Which figure no. is this? (Refering to Fig. M.1 p.209) I've shot air thorugh each opening and the piston hasn't budged. Help!
S.L. LaPaugh


I can't remember exactly which port that is, and I don't have a Bently. However, I do remember that getting that out was the worse part of rebuilding my 77 MC.

Do you have the switch out of the MC body? I think the rod on the switch may be able to block the differential piston from being removed.

In my case, no amount of air in any port would move the piston because it was stuck in place. I ended up removing everything I could out of the switch port, and then got it unstuck by prying on it. I have a vague recollection that I first moved it the wrong way (further in the bore since that direction is more accessible with a drift) before I could get it moving outwards.

Sorry I can't be more specific. I don't remember all of the details.

C R Huff


when i rebuilt mine, i tried to get this piston out but was unable to mowe it, neither WD40 nor compressed air helped, so i let it stuck and rebuilt the rest of my MC. No problems within 5 years and change to silicone fluid.
The warning light made an ideal low presure oil warning light for me. I just put an adator fitting to the oil pipe connector with a switch from another engine on it, connected the two thin black/white wires to this switch and it works.


Has anyone had good results with the Cardone rebuilt? It is less than $100- and the website has a coupon for store pickup or free shipping.

I've had good results with their rebuilt calipers. RAY

This thread was discussed between 10/12/2008 and 13/12/2008

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