Master cylinder puking!

[Josh]

I have the stock dual chamber master cylinder on a 67. I am finding that the rear chamber is spewing its contents forward into the front chamber then is starts leaking out the lid and my brakes fade in a bad way and getting worse. At first I thought it was the bad wheel bearing I just changed that was boiling the line on the axle and blowing it back out, but I fixed that and I sill have the brake problem. Master cylinder valving shot? Thanks in advance.