Hi Everyone,

I've had a recurring problem with the past two master cylinders that I've installed and I really don't understand what is happening and why it's happening.
Here's the problem. I've installed two master cylinders and after each installation I've found that the master cylinder leaks both vacuum and brake fluid through two open ports at the base of the units. The first time that this happened was about ten years ago. I ended up making a quick repair by sealing up the ports, not really understanding what the ports were for. The brakes worked fantastic for years. During a resto I decided to replace both the brake booster and master cylinder with rebuilt units. Well, once again the same problem occurred. I would hear a noticeable vacuum leak while the vehicle was running and would find fluid leaking after the vehicle had been parked overnight. I once again sealed the port, but this time with an expanding foam. It was only suppose to be a temp fix.
I'm now taking the time to fix all these little problems, but really need the help of the Camaros.net patrons.
Could someone please tell me what the purpose of the ports is and how I can remedy this problem?

Here are some pics of the master cylinders and the problem ports:
http://www.shutterfly.com/osi.jsp?i=67b0de21b376ef8a2502&notag=1

I appreciate any help. Thanks so much, Paul