I’ve removed the brake cylinder from the backing plate, but now I need to free the pistons in order to get it all working again. At this point they are rusted so bad that there is no movement even when connected to an air compressor.
To do this you have to ‘sand’ the inside of the brake cylinder with suitable sandpaper (I used 150 grade) to get back to a surface, I used my thumb and sandpaper as the only tools as it fitted quite well into the cylinder.
You need to keep doing this until the finish is somewhat normal so that you can move the pistons and therefore get them out of the cylinder.
This was a slow, dirty, laborious process as my pistons were well and truly seized. In the photo above you can see some progress, the piston has budged a bit inwards, and I’ve removed some surface rust with the sandpaper and oil.
Once you get one side fairly rust free, start on the other side, as the pistons may have to go through in that direction to exit.
After sanding away the rust, and then tapping the pistons in with a piece of wood and a hammer, the pistons (and associated parts) popped out eventually.
In the picture below you can see the pistons on either end, next are the rubber seals (replace them) then a spring which has two cones attached to it.