Volkswagen Polo brake master cylinder replacement

You will need: socket head or “13” wrench, flat blade screwdriver, pliers, medical syringe and a special “11” wrench for brake lines.
1. Disconnect a wire from the minus plug of the storage battery.
2. Press the brake light switch harness block retainer and disconnect the block from the switch.

3. For convenience, remove the reservoir of the main brake cylinder
4. Unscrew the nuts securing the two pipelines to the main brake cylinder and move the pipelines aside.
Tip : Plug the pipes in any way possible (for example, by putting protective caps on the ends of the valves to release air) to prevent leakage of brake fluid.
5. Turn away two nuts of fastening of the main brake cylinder to the vacuum amplifier...
6. ... And remove the main brake cylinder.

7. Remove a rubber sealing ring from the case of the main brake cylinder.
Warning: The sealing ring of the master brake cylinder must be replaced with a new one each time the connection is disassembled.
8. If during operation there was a leak of brake fluid through the connecting sleeves, remove the sleeves from the holes of the cylinder body

Warning: The connecting sleeves must not be reused, replace them with new ones.
9. Install the brake master cylinder and removed parts in the reverse order of removal, fill in the brake fluid and bleed the system. 

Source: http://www.polosdn.ru/news/glavnyj_tormoznoj_cilindr/2012-06-15-118