Bleeding Master Cylinder w/Syringe (W123)---How?

[iladelf]

So, my '81 300d (w/84 eng/trans) is having issues leaking brake fluid that I have to top off when the "brake" light goes on. It appears to be leaking from the master cylinder, as I see residue on the booster, and the paint is either ate away or getting eaten away on said booster. This past spring, I replaced both the rubber grommets on the bottom of the MC, and the o-ring between the MC and booster. Seemed ok until the problem showed up again recently.

My question is this; I'm replacing the MC and booster, but...how do you perform an MC syringe bleed on one of these reservoirs? I think it's a great idea, but...aren't there 3 different brake lines coming off a W123 MC? Reason I ask this is that I got confused, looking at what to buy online, MC-wise. I clearly see the two fender-side ports, but there's a third on the engine side; where does that go? (See the photo in the link below in reference to the 3 ports I'm referring to. You'll have to scroll down and select the FTE or Meyle to clearly see this.)

1981 Mercedes-Benz 300D Base Sedan - Brake Hydraulics - Page 4

Looking at the video below, it seems the syringe bleeding procedure would be very similar for our W123s, since we only have a single cap covering both the front and rear brake reservoir compartments. Again though, does that mean you'd have to do the syringe procedure for the two fender-side ports AND the single engine-side port?

https://www.youtube.com/watch?v=OUvBHnOh9ao&t=2m22s

For the record, I looked around the forums, used my Google Fu and looked at the CD W123 manual I've downloaded, and really couldn't find an answer to my question.