I don't want to be the person that has to say your wrong, but I guess I will have to in this case.

You can buy a rebuild kit from any auto parts stores. I got one from Checker for like 8-9 dollars. It comes w/ everything you need.

A new piston, spring, and all the O-rings.

After you take out the master cylinder all you have to do is take it all apart (real easy) and install all the new parts. When you take out all the parts inside the master cylinder all you are left w/ is a piece of machined metal. You replace everything inside it using the kit. It is real brain dead stuff. (Anyone can do it) just take it apart systematically and put it back together the opposite way you took it apart. I rebuilt mine and it has been working well ever sense.

$8 solution vs. 100+ solution

Whole job only took an hour

Hope this helps James