Master cylinder grief

[RC Ringlien <rringlie@isd.net>]

Patrick and other listers:
   Finally found a used MC to try on my 89 200. After installing,  I was
under the back end bleeding the rear brakes, with my wife pushing the
pedal, I hear this fluid running on the floor.  My HYDRAULIC reservoir
overflows all over.  I start the car, level goes down, shut engine off
,resume bleeding process and level goes back up.  Is this normal?  Am I
discharging the bomb through the booster with all these pedal to the
floor actions?
   It was getting late and the mosquitos were hungry so I quit for the
night and didn't finish bleeding tho I finally had some pedal.  Any
ideas on this weird occurence?  
Bob Ringlien