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MG MGB Technical - Late brake master cylinder problem

I currently have a late brake master cylinder on my bench that I am trying to strip down so I can change the seals. It is the late dual circuit type that works with the direct acting servo.

The first circlip came out without any trouble. I have removed the first piston and the spring that sits in the first half of the chamber. Now for the difficult bit.

Between the out lets half way along and the end outlet there is a second piston and another spring. These feel as if they are held in by a further circlip. Am I correct? If so, how do I get it out?

Also there is a shuttle in a balance tube between the outlets. This will trigger the warning light switch if there is an imbalance in pressure. I have removed the brass plug at the end of the balance tube but it looks as if there may be some thing U shaped holding the shuttle in. Am I correct? If so, how do I get it out?

My biggest concern is the problem in the master cylinder itself.

Thanks

David
David Witham

David,

You need to remove the reservoir, there is a pin fitted through a hole that locates the second piston. I don’t remember a problem with the shuttle piston, once the switch is removed it should pull out.

Geoff
Geoff King

Geoff,

I don't have it in front of me, because I am at work, but is this pin under the one of the two resevoir seals?

The reason why I ask is that I have removed the resevoir but not the seals and I don't remember seeing the pin.

Thanks for your help

David
David Witham

David,

Yes, the pin is under the seal.

Geoff
Geoff King

Thanks Geoff.

Last night the pin came out easily and the second piston plus spring could then be removed.

I still can't get the shuttle out of the balance tube. The switch has been removed as has the end plug with its intergral perforated distance tube.

I am concerned not to do any damage. Has anyone got any ideas?

David
David Witham

You could try compressed air. Personally, i got stuck at this point a number of years ago, replaced everything else, and then it didn't work. My lesson was that it was easier (and safer) to just buy a new MC.
Ira Spector

Ira,

Thanks,I will give compressed air a try.

There is a substantial price difference between the seal kit and a new master cylinder. I am confident I can reassemble the master cylinder to a high standard. I have done this before with other ones.

David
David Witham

This thread was discussed between 17/09/2003 and 19/09/2003

MG MGB Technical index

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