Brake bleedung

[LolHare]

On leaving a car show the pedal went to the floor, back home I discovered the rear of the master cylinder was empty which does the rear brakes, I can't see any apparent leaks so tried to top up and bleed again with success at the passenger side but the drivers side has no fluid out through either of the 2 caliper nipples but it has fluid at the line just before the caliper, I do have a pedal now and the brake does work on the problem side
Im confused at whats with the caliper and why the fluid emptied in the first place, it could have be slowly over time as it obviously wont fail until the last drop so to speak

 

[Roscobbc]

C2's and C3's are notorious for weeping caliper seals - especially the OEM lip seal type. 'O' ring caliper seals have less of an issue but caliper must be cleaned thoroughly before replacing pistons with 'O'rings. The brake system incorporates ferrous components (calipers and master cylinder) and if the car is stored in damp conditions and/or infrequently used the brake fluid will absorb atmospheric moisture, degrading the brake fluid and creating internal corrosion to the ferrous components and damaging rubber parts like piston seals. If storing the car outside or in an unheated location - change brake fluid regularly,

 

[Oneball]

The fluid has to have gone somewhere. Like Rosco said it could have leaked past the calliper seals. So check them as there will be evidence even if it’s leaked over time, you’ll still see something. It can’t just disappear.

That caliper could be completely corroded inside but even if it is if there’s no evidence of it leaking you still need to find where it’s gone.

 

[antijam]

As above, since the master cylinder was empty you've got a leak somewhere. I had a hard pedal on my C3 but noticed one day drips on the ground in front of the left rear wheel. I checked the master cylinder and the rear reservoir wasn't empty but the level was well down. I eventually traced the leak to a crack in the front to rear brake line where it rises up in front of the trailing arm. I replaced all the brake lines - see here..