Master cylinder rebuild

[timbomath]

Getting the brakes up to snuff on my "new car" ('79 MGB)it was apparent the seals in the master cylinder were shot so I decided to rebuild it. The last seal on the primary piston was a little tough to get in but otherwise things went ok. (Except for the corroded pins breaking off in the pressure failure switch.)In the rebuilding process after I had taken out the pressure differential piston a little plastic tube about 3/8" long by 1/4" in dia. with two small rectangular holes on opposing sides fell out. I could find no mention of this in the Bentley book but put it back in hopeing there was no importance as to orientation of the holes. I don't know if there is any relationship but after I had it all assembled and started to bleed the brakes, backing out the pressure failure switch as per manual, this caused brake fluid to shoot out from around it. Even when tightened down brake fluid leaks out a channel that is cut in the threads and base of the switch. Is there a seal for the switch missing? Would it hurt to eliminate the switch and put a plug in the hole? I really don't need a light to tell me when I have no brake fluid pressure. I realize many people just replace the master cylinder - and I may end up doing that myself- but I was just curious if anyone has had experience with these and could shed a little light on the subject for me. Thanks.