Hi Lizem,The 124 manual states to drain the master cylinder down to about 10mm then refill.If you use a Mity-vac to bleed it draw 80 cc from each wheel or 10 pedal strokes if you do it the old way.Like Mihngram said 2 pints or 1 liter should be plenty,don't use old brake fluid, buy fresh fluid.Brake fluid is hygroscopic and an unsealed container in a damp shop will absorb moisture in a few months time.Good luck.
1985 380SE- 160,000km 'Blistu' - Sold
1988 300CE- Eva,my garage mistress
2007 R350 4matic- The Black Pearl
2011 Ford Ranger-Work truck
1974 25' Trojan Sea Raider- 'Grannyknot'
2002 215 cm Atomic DH skis- Canadian SDH record holder, 175.5km/h- Vars 2010