Brake cylinders/backplate
I had a little problem with a weepy rear brake cylinder, and decided it would be a good time to tidy up the whole rear brake. I discovered both sides were affected, and bought a pair from Rossefields at a reasonable £12 each. I got new shoes as well as I was worried about fluid contamination, they were a dearer £16 a side. The rear shoes hardly wear at all and are not a common replacement item.
Anyway, to get into the rear brakes, proceed as for rear drum removal here.
Either clamp off the flexible brake hose or work out a plug for the brake union, or it will give you a puddle of brake fluid on the floor. Remove the bolt holding the union together at the back of the brake cylinder (14mm ring spanner) keeping track of the 2 copper washers.
If you are just replacing the cylinder in situ you will need out the 2 M6 screws on the cylinder, and I reasonably sure you'll need the brake shoes off as before, though possibly wedging the shoes apart would do the trick. 10mm spanner or socket if you have room. One of them holds the handbrake lever spring.
If you want the whole thing off, pull the hub bolt all the way out so you can swing the hub and suspension unit around, it gives better access to the bolts. The 4 bolts need a 6mm hex key, I don't know how I would manage without my ball driver set! You can see how much surface rust is on this metal. It was originally cadmium plated I think, not much remains after some damp and road salt for a few years. Here is the inside:
Doesn't look too leaky? Look closer:
I had a look in the cylinder - not too good for a fairly young car:
Anyway, with some cleaning up in mind, I degreased the backplate and dried it:
After this it was given a SEVERE talking to with a rotary wire brush, the 11000 rpm angle grinder twisted type, then a light coat of zinc primer and some fairly hard wearing polyurethane paint. At this point I was working against the clock a little, so I haven't any photos of the finished bare plate. It looked a LOT better :o) I also cleaned up the springs and shoe steady pins with an acid type rust remover and wire brush. Here it is back in place - actually a couple of weeks later and with a little road dirt on it:
You can see the four mounting screws near the centre. Reassembly was straightforward - I used some thread locking compound on the mounting screws, again after wire brushing the old stuff off the threads. Couple up the hydraulic line again and bleed the brake. Grease the handbrake pivot generously but don't force any through the backplate, there isn't a seal where the lever goes in. I had changed the brake fluid in the rear pipes earlier. This is what came out. Indicates how the brakes had been neglected in the past perhaps? It should be clear and honey-coloured:
This resembled VERY dirty pondwater, totally opaque and much sediment in it. YUCK!
I like Waxoyl rustproofer, so used some of this on the OUTSIDE of the backplate, nuts and cylinder. Don't get any on the drums or shoes, it will melt when it heats up and the brakes will slip if it gets on the lining.
The handbrake will need adjusting, in fact with new shoes you may need to slack the main adjuster off just to link up the arms again.
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