Brake servo

[CoolVT@aol.com]

I rebuilt my brake servo 4-5 yrs. ago and it was great for a few years.  Last
year it swallowed up all the fluid (no visible leaks).  What part should have
been replaced and was not included in the rebuild kit?   It seems like someone
on the list mentioned something about ceramic disks or something of the sort.
  Where are these needed parts available?   Thanks in advance.  Mark L.