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Tips

MGB Master cylinder

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Bob Claffie

Bob Claffie

Jedi Knight
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You guys did such a great job working me through my seat adjustment problem I'll give you another try.

I'm just about to start replacing the brake master cylinder (1974 B). Current cylinder has an internal leak and does not work on the front brakes ! The manuals don't seem to give much detail so I'm wondering about tips and pitfalls. Doesn't look like there is much room to work in there especially having to dodge the hood support every time I lean in. Bob
 
Bob, Getting it out is the easy bit compared to a rebuild. The lower bolt holding the master in the bracket can be removed with a swivel on a 1/4 drive. The front plunger will need to be pushed in and the master turned clockwise and back to get it out. Use a turkey baster to get as much fluid out as you can.

Do you plan to replace or rebuild? The plastic ring at the front is not going to co-operate. I drilled a couple of holes with a 3/32 and used a long #6 screw in each hole, pull with pliers on each. It works most of the time but be careful not to scar the shaft and only drill through the plastic. Now you need long needle nose pliers that have been ground down to get the "C" clip that is 3 inches inside the cylinder between the wall and plunger. Home free after that.

Have fun, Wayne
 
I thought I had posted here yesterday that, when I was a BMC line mech in the 70's, we blew the m/c pistons out with compressed air.
Bob
 
Bob, the duel ones have two clips holding everything in place. The old singles just had the retainer clip in front and then you could blow it out. The MGB is the bear to rebuild and takes a couple of times just to be able to get it out of the bracket with out taking it all apart.
Wayne
 
I do now recall having owned a ground down needlenose plier for this purpose, but I don't recall the problem with the nylon. That's 40 years for you.
Bob
 
Thank goodness that's not my problem, I am replacing the MC not interested in rebuilding one.

Try as I might I couldn't maneuver the old MC out no how. i ended up taking out the whole brake and clutch assembly. What a b*t*h. Not sure I have the clutch hydraulics sealed yet.

And then I stripped one of the brake lines and the auto parts store sold me a replacement pipe with the wrong size fittings on it ! Tomorrow (Mon) I will attempt to bend the new pipe in some kind of configuration to fit Thankfully these alloy pipes bend easier than the OEM steel pipes. Getting tired of this job, want to move on to more "fun" repairs.
 
Bob, Sorry it turned out bad for you. It's one of those things you have to hold your mouth right, I guess. Glad you replaced the M/C, been a lot of years with water setting in the bottom of these cylinders and no way would they seal like I would want, just enough pitting to be of concern.

On the fittings, they should go together by hand and the trouble is that most have been over tightened and the end that pushes against the flare has been spread and is touching the threads. Back it away from the flare and lightly file the flat end to get rid of the taper, you will be able to run it almost tight now.

Wayne
 
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