My brother and I just swapped out the rear pads on my '79 450SL, and then went to bleed the rear brakes. Sucked the old fluid out of the reservoir, poured some fresh fluid in, went to start with the right rear. Doing the normal pump-and-bleed procedure, my brother on the caliper bleed screw and me on the pedal. After the first 15 or 20 pumps/bleeds, the pedal stopped pumping back up and we stopped getting fluid out of the bleed screw.

So, we took a closer look at the master cylinder and found that it has different compartments for the front and rear brakes. There's only one place to fill (which seems to go to the front brakes portion of the MC), and then there's a little vent from the top of the rear reservoir back to the MC cap. I don't know how to get fluid from the main/front portion of the MC reservoir to the rear portion of the MC reservoir.

Searching a bit on line, the only thing that seemed possibly related I found here: https://mbworld.org/forums/showthrea...brake+bleeding . However, as far as I can see the '79 doesn't have ABS so it doesn't seem that could be the problem, as it was in that guy's case.

So, what trick are we missing to get the rear reservoir to fill up so we can bleed the brakes? I appreciate any assistance.

PS - Please pardon me while I double post this.