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MG MGB Technical - Brake cylinder replacement

Hi guys, well just had a great time doing 650 miles around Normandie in my MGBGT 1967, she ran faultless and did me proud, got a little hot sometimes but no problem.
Anyway now I'm home I think the old girl deserves a bit of TLC, I noticed as light drop of brake fluid on passenger side read wheel, so I have two new brake cylinders ready to fit.
Question, having taken off the drum and inspected it , it is wet so leaking probably, so it'll change them both sides, is there an easy way do do these, my backplates have three retaining springs must be later model, they look a pig to get off and probably a bigger pig to put back on, if I release them and just take off one brake shoe I should them be able to get the cylinder off, is there a way to disconnect the cylinder without losing too much fluid, I will still have to bread afterwords, and is there a trick to getting those springs back on?
Any helpful tips would be appreciated, you guys always come up trumps and save be some knuckle grazing!

Cheers Jack.
Jack New Forest

I did mine this summer because it failed the norwegian MOT test. Not a difficult job, the springs came off without much of a fight. I clamped the flexible brake hose and hardly any fluid came out.

The hardest part was getting the cylinder retaining clip on.
M Ratcliff

Jack, The springs are no problem, take a photo with your mob phone first and be patient. The real ball aches are the slave securing circlips and I've never found the secret of doing them without a lot of expletives!!!. As for fluid loss, put a piece of plastic bag under the screw cap on the master cylinder and then it depends whether you have a rubber flex or a braided flex. Rubber you can clamp before you disconnect, either with a proper clamp or two sockets on a vice grip. I also have a couple of female unions with the ends plugged which i screw on as soon as I have disconnected the lines.
Allan Reeling

Hi Jack,

This link has some good advice.

When I did mine, I completely dismantled all the brake shoes, didn't want to get fluid on them, plus more room to work.
If you remove the existing clip, then quickly undo the brake line, insert the new cylinder and refit the brake line you lose very little fluid and only the rear brakes need to be bled.
I didn't fit the e clip the way that the article says, but slid the ends into the groove and with a pair of multi grips forced the clip on. Took a couple of tries and had to retrieve one clip from across the garage, and the brake line in the way made it a bit more challenging, but all worked in the end.

Herb Adler

When you remove the brake cylinder, insert a small length of vacuum line with a bolt in one end, over the brake line. This will prevent you from losing all but a very small amount of brake fluid and no air will enter your master cylinder. Installing the circlip is an easy task if you install the brake cylinder and then hold it in place with a pair of Vicegrips mounted on the axle flange and pushing against the brake cylinder. This will hold the cylinder in place while you install the circlip. Doing it this way frees up your hands from trying to hold the cylinder in place while you try to wrestle the circlip into place at the same time. Bleeding the system requires that you simply top up the master cylinder and gravity bleed the two rear cylinders. No pumping of the brake pedal required. RAY
rjm RAY

Last year when replacing a cylinder, I gave up the unequal struggle with the stock circlip and used a suitable sized piston circlip I had around. Might even have been an MGB one. Whilst not of the same proportions as the original, I took the view that it was just to hold the cylinder in place, as it can't move that much anyway without the circlip, and isn't under any stress. It seems to do this fine and two MoTs later!

P A Allen

"take a photo with your mob phone first and be patient."

Assuming they are correct to begin with ...

The third outer spring is pretty heavy. I use a large pair of pliers with one jaw against the end of the spring below the handbrake lever, rearmost end, and the other jaw against the edge of the lever closest to the drum. Squeeze, and the end of the spring pops up into the hole. Then you can use the pliers to lift the spring out of the hole. Replacement is a matter of pulling on the straight part of the spring until the curved end drops into the hole, then squeezing the top of the spring and the bottom of the lever to pop it all the way in.

Also important is to get the shoes correctly orientated. This is when a point on the drum, when travelling forward, passes over the 'empty' portion of the shoe before reaching the friction material, both shoes both sides.

As for gravity bleeding, well, air travels upwards when left to its own devices and the cylinders are the lowest point of the system. Use a hose clamp on the rear hose then have someone operate the pedal with the cylinder bleed nipple open, and release the clamp. Hopefully that will be enough.
Paul Hunt

The easy way to put the pull off springs back into place is to use a pair of snipe nose visegrips. Gravity bleeding is no problem especially if you are working on your own. But before you bleed the rear brake tighten the adjusters up, this will make bleeding easier as there will be very little air space in between the pistons, obviously reset the brake adjustment.
john wright

Once you have used a small flat-tipped screwdriver to twist or pop the last leg of the E-Clip into place, you will notice that all three tabs are not seated fully home. You can risk using a screwdriver to force it home, but that approach risks ruining the E-clip. Instead of using a screwdriver, place a socket over the brake line boss of the slave cylinder. Thread on a 3/8"-24 nut fully home onto a 3/8"-24 machine bolt, and then slip the washer on after it. Install the 3/8"-24 machine bolt / nut / washer assembly onto where the brake line would normally go onto the slave cylinder (this will all be placed through an 11/16" socket). Note that there is no need to torque the machine bolt tight with a torque wrench. Once the machine bolt has seated, turn the 3/8" nut and washer against the socket. This will push the E-clip home. Do this until you see all three tabs engage the groove on the wheel cylinder. Give the E-clip a few gentle taps with a lightweight hammer and drift it inward in order to ensure that all three tabs are properly engaged and fully seated. Take note that early Honda Civics and Honda Accords have a nice rubber boot seal that is found on the adjuster studs of their rear brake backing plates. Purchase a pair of these rubber boot seals from a Honda dealership. They fit perfectly over MGB rear brake adjusters, keeping dirt and corrosion off of them.
Stephen Strange

Thanks for all your comments and help guys, I'll be attacking it today, so listen out for the argggggggg!
None of that Jack keep positive and be patient!


Jack New Forest

I thought we'd been through the cleaning of the coolant system on your car to help prevent it getting hot but perhaps it wasn't on your car
Nigel Atkins

This thread was discussed between 29/08/2013 and 31/08/2013

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