The BX's handbrake was slowly getting worse. The handbrake lever need to be pulled almost verticle for it to work. I decided it was time to look at when Ang decided to let the car roll down the drive & across the road because the handbrake wasn't pulled on hard enough (obviously this was my fault LOL). First of all ensure the car is well supported. I used a bottle jack to lift the corner, then supported the corner of the car on a 6ton axle stand:
The front left caliper appeared not to be winding on at all, so wouldn't take up slack as the brake pads wore. I pulled the ratchet side of the caliper apart. It appeared OK, however the handbrake utterly confused me, I just couldn't see how it worked. In frustration I decided to pull the entire caliper from the car and dismantle it. It only two 19mm bolt to remove the caliper (one the brake pads have been removed).
The easiest way to remove the flexible brake line is to loosen it slightly with a spanner, the rotate the caliper itself to undo the line. Don't forget a drip tray to catch the dripping LHM.
In order to get the piston out of the caliper, just used compressed air. It'll pop out easily enough.
1. You will need to pry this retaining ring out of the groove in the piston.
2. The metal plate then lifts out
3. This bearing then lifts out.
4. Finally this this internally threaded cylinder with the spring around it lifts out.
Now I've had the entire caliper apart, and it still makes no sense how it worked :-( ....
Then I discovered this broken bit of wire in the caliper (circled in blue):
The bit of wire circled in blue above was in the bottom of the caliper housing. As soon as I found this it made immediate sense how the handbrake works. The spring on the cylinder should look like it does with the green line. This allows it to lock in the piston hole shown below.
With the tag broken off the spring, it wouldn't allow the piston to 'wind' out of the caliper as the brake pads wore. This was due to the fact there was no tension being applied by the un-contained spring.
I bent on new end onto the spring, and re-assembled the caliper. The handbrake now works quite well again!! Don't forget to bleed the brakes once you re-assemble them!!