Classic Brake issues

[MiniVespa]

So my brake fluid was very low on my Mini. Coming home from the all British car show I noticed my brakes pretty well shot. It braked, but I was pushing air into the lines and I knew I was going to need to bleed the brakes and all that. I took it up to Olathe Toyota today, and my brother who is a tech put it up on a lift, we did the bleed, replaced with the recommended DOT 4 fluid and all was good. Sort of...

On the front right side, the disc brakes looked good. However, the left side, there are pieces within the caliper that are missing. I have no idea how this happened. Here are pictures of it, the first being the correct set up on the right, the second the left.



What are the guts that I am missing called? I see that I am missing a pin as well. Is this the part that needs to be replaced?

[Minidave]

Yep, that's it, but that won't make you lose fluid or pump air into the system - you have a leak somewhere or a bad master cylinder. Check the carpet down by the pedals and see if it's wet - if so you need to order a new master cylinder too. Also check your rear wheel cylinders, they go bad and they're not expensive or hard to replace, but if your rear shoes are wet with fluid you need to replace them - ask Counterfit Mini how, she did hers not too long ago!

That black part is just an anti-noise anti-rattle piece, the cotter pins hold the pads in place.

[monza]

The master cyl is notorious for going south. They are cheap though, and really easy to replace.