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Master Cylinder Disassembly

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RDKeysor

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Pursuant to opinions from forum members that my '60 BN7's master cylinder needed a rebuild or possibly replacement, I bought a rebuild kit and sought to pull the innards out after first removing the push rod. That clearly wasn't going to happen. Having now removed the master cylinder, I find I am unable to remove the cylinder contents. Looking at the schematic in the BMC shop manual, page MMM.5, I have removed the parts numbered 4 through 7, basically the push rod and related parts. However, I do not find or can't identify part 8, the end seal. Looking at the open end of the cylinder, I see the cupped end of part 9, the plunger. I can move this deeper into the cylinder, but it makes a firm metallic sound when it is released under the return spring pressure. I have tapped around the metal portion of the cylinder that encircles the plunger, and, even under magnification, cannot see any seam or detect any movement. I even placed the cylinder casting in my vise and inserted a socket, tapping that a bit against the inside shoulder looking for movement. Nothing. Obviously I have once again overlooked something obvious and invite solutions. For posterity, I'll add this: the master cylinder is best removed by taking off the rear air cleaner. After that one has only to remove the two hard brake fluid lines and the bolts visible holding the master cylinder inside the engine bay. DO NOT TRY TO REMOVE THE NUTS IN THE FOOT WELL. THEY ARE WELDED TO THE FIREWALL. But I did try, they are Whitworth, and they aren't coming out.
 
Item 8 is no longer used. In my case, built up crud was keeping the piston from exiting. If the air per above doesn't work, you may need to carefully scrape this area.
Since you've removed the circlip (5), is there a possibility the cylinder is so worn the piston is clicking against a wear ridge?
The nuts are welded to the pedal box.
 
Eureka! Found a suitable plug for the supply line hole, hooked up my electric air pump, attached a tapered fitting to the chuck, put a sock over the business end of the cylinder, and switched on the pump. I watched the pressure build on the pump gauge and heard a muffled pop, sort of a champagne cork thing. The ejected plunger shows only minimal discoloration, and the cylinder bore looks smooth. I remain a bit puzzled at its reluctance to expel, but expel it did. Will extract the balance of the cylinder content this afternoon preparatory to rebuilding and reinstalling the master cylinder. Again, thanks to the usual suspects!
 
You do know that a NEW master cylinder costs $77, don't you? Rebuilding them can be rewarding but...
 
I don't know whether the master cylinders - clutch and brake - that I recently bought came from China. But the new brake master cylinder leaks back into the passenger compartment, and I have no reason to believe that the clutch MC will be any better. I have no confidence in these units. They are coming back out of the car and I will rebuild the original units.

Lets hope that the rebuild kits use decent rubber. I recently had a conversation in Cuba with a man standing next to his Lada, with the wheel off. He was waiting for a mechanic who was going to install a Kia wheel cylinder on the Lada. He showed me a handful of rubber wheel cylinder seals that he had bought, but he said that they were all junk and leaked even when new. This sounded too familiar, after my recent experience. According to him, they can't get decent brake parts in Cuba. He was hoping that the Kia part would solve his woes. I hope that they use good rubber in the rebuild kits and not the same stuff that comes in the new master cylinders.
 
The rebuild kit I bought from Victoria British was identified on the poly bag as UK sourced. I found the internals on my MC, including the bore, in very good condition, but I went ahead and installed the rebuild kit with the supplied lubricant. I am now poised to install the servo kit VB off sells, something that wasn't offered on the Mark 1. I do note that my MC bore is 5/8", and later cars (some of which got servos) used 3/4" bores. Or so I understand it. There has to be a reason for that. I might have tried Pegasus, as Healey Rick suggests, but I had already ordered my parts. I have had good luck with Victoria British (no financial connection with me) components, though I have also had dealings with Moss and Austin Healey Spares. I acknowledge being a Healey novice, though I owned my first one in Ohio back in 1963.
 
RDKeysor said:
The rebuild kit I bought from Victoria British was identified on the poly bag as UK sourced. I found the internals on my MC, including the bore, in very good condition, but I went ahead and installed the rebuild kit with the supplied lubricant. I am now poised to install the servo kit VB off sells, something that wasn't offered on the Mark 1. I do note that my MC bore is 5/8", and later cars (some of which got servos) used 3/4" bores. Or so I understand it. There has to be a reason for that. I might have tried Pegasus, as Healey Rick suggests, but I had already ordered my parts. I have had good luck with Victoria British (no financial connection with me) components, though I have also had dealings with Moss and Austin Healey Spares. I acknowledge being a Healey novice, though I owned my first one in Ohio back in 1963.
Click to expand...

RD - the 3/4" MCs are for drum braked cars; servo'd BJ8 uses a 7/8" cylinder.

Rich Berman, who posts here, has a very comprehensive gallery of photos:
https://plus.google.com/photos/110087349657726745747/albums/5528813397849858337

Scroll down to picture 635 or so and you'll see the servo installation.

Maybe Rich will read this and let us know how the brakes work with the 5/8" MC and booster.
 
I used a 3/4" BN4L MC but added servo and new plumbing to make it work. All was new and sourced from AHSpares. In year 1 brakes were fine. Year two I noticed brakes got soft and sometimes needed pumping to bring up pressure and make them work. I tucked her away for the winter before I got a chance to localize the issue. So not sure what to say except that it worked without problems year one. Note:I did use disks on front and up-rated all brake cylinders to BJ8 style. The first brake problem I had was the rear drum shoes even though they were new, they were a full 1/8" thinner than spec and the left one "locked on" after using e-brake on a steep hill. After releasing the adjuster, the pin blew out of the cylinder, releasing brake fluid, pressure and caused complete brake failure. Thank G-d for manual transmissions and still functioning e-brake on the right rear...made it home without incident. I was thankfully only 2 miles from home at the time. My father-in-law was in the passenger seat and barely noticed, except for the sweat on my brow....
 
IMO, adding the servo should not be necessary with the stock 5/8" MC.

Last year, a friend installed the Denis Welch front disc kit on his BN6, changing out the MC from 3/4" to 5/8" and changing the rear wheel cylinders -- both these brought it to non-servo disc brake spec. He uprated to front pads to ceramic, broken in properly. The car stops fine without a servo.

It might be best to get the MC rebuilt and drive the car first before deciding whether or not to install the servo. The servo may be a solution in search of a problem.

Totally agree with Rick re Pegasus. They sell genuine Girling cylinders and rebuild kits.
 
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