OK, I decided to go with the following advice from fellow forum member Duke and started with the front left wheel:

That's old school single master cylinder advice, but it wasn't even that good decades ago. With either a split or single system the quickest way to expel old fluid or get new fluid into a dry system from the M/C to the junction block is the shortest route, which is usually left front and left rear for most split systems and left front for single systems. Then go to the next shortest line, and you'll need to make the complete circuit about three times.

But the bottom line is that it doesn't really make much difference where you start. You'll eventually get the system bled and filled.

If manually bleeding be careful not to let the rear reservoir go dry, or you are essentially starting over. On my 201 it's tough to see the rear level, and I think other contemporaneous models are similar. The rear level can only be seen on the inside side, extreme rear of the reservoir.

When the rear res. gets low, fill the res. then wiggle it back and forth to get the fluid over the baffle that separates the front and rear section until the rear level is equal to the front and continue bleeding.

Duke

I pumped the pressure bleeder up to 13 PSI, then slowly pumped the brake pedal 3-4 times...some fluid has come out but still no steady flow. I'm thinking of hooking up a hand held vacuum pump (mine is similar to mityvac) so that I can simultaneously use the pressure bleeder AND vacuum. Do you think this idea might get the fluid flowing???

Here's photos of my Harbor Freight vacuum brake bleeder. I'm thinking of using this in conjunction with the power bleeder.

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to get a good bleed, get some tubing and a bottle, fill the bottle with brake fluid or even water a bit, connect the tubing to the bleed nipple and make sure the tube is all the way down in the bottle.

hang the setup in a way that the bottle is above the slave cylinder but still below the master cylinder level. This way the liquid in the bottle acts as a one way valve and air cannot be pulled back either.

I have bled numerous systems like this and all have performed great.

dont overstroke the cylinder, gentle tiny strokes to prime the system and then only half pedal strokes to bleed it.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

I'm thinking perhaps the back reservoir is not topped up with brake fluid. How can I tell if it is full?

...as I decribed and you copied and pasted in your original post. I believe it's very common for guys to empty the rear res. because they don't know how to read the level. Its tricky!

I siphon out the front res. as much as possible, which makes it easier to see the rear res. as I described. Then I put a little fluid in the front res. and bleed the rears until the rear res. is near empty. Then I fill the res. to nearly the top of the fill port, then wiggle it back and forth to get the fluid over the baffle and into the rear res. that I monitor as described.

...repeat the procedure until I've flushed through about a quart of fresh DOT 4.

Duke

You do not need a pressure bleeder if you are using the brake pedal method since the brake pedal actuating the master cylinder will produce far in excess of the 13 psi from the pressure bleeder. If you have loosened the bleeder valve at a wheel cylinder and still do not get a strong steady flow when depressing the brake pedal there are one or more obstructions in the system or the master cylinder is not supplying enough pressure. Start by replacing the flexible brake hoses.

P.S. Now i feel like a complete idiot for having wasted my time responding to this thread before I scrolled down the page to see that the OP had previously begun another thread on the same subject and had received sage advice on solving his problem. Duplicate threads are neither helpful or desired.

The brake hoses are brand new. I'm now considering purchasing a new master cylinder for the car. I've checked out some of the local car parts stores for pricing/quality. Of course, ATE is OEM but I'm considering going with a car parts store special. Has anyone had any experience with NAPA, Advance Auto parts, Autozone, O'Reilly or Pep Boys Brake Master Cylinders?

Why would you replace master cylinder just because you dont know how to use the pressure bleeder. I would think it would be cheaper to take car to a shop that can bleed the brakes for you then you wont have to replace parts that dont need replacing. brakes are the most important part of the vehicle there is no need to go if you cant stop
You can be cheap any where in the car just dont skimp on brakes

I checked the service records last evening. It appears the brake master cylinder has NEVER been replaced since the car was new in 1991. Twenty-five years of driving and wear and tear, it certainly can't hurt to replace the master cylinder do you think? You are correct, brakes are a VERY important part of the car, therefore it seems to me that it would be prudent to replace it rather than worry about it's integrity.

Again, has anyone out there in Mercedes land had any experience with brake master cylinders from Advance Auto, NAPA, Pep Boys, O'Reilly's or AutoZone??

use a small flashlight and put it up against the plastic of the reservoir and shake the thing a little, you will see the level.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

They would work - NAPA would be my first choice as their parts are slightly better than others.

Make sure your hard lines are not corroded anywhere either.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

You are correct there is nothing wrong with having new brake parts. That said if you have trouble bleeding the system with a master cylinder that is good why would you think that a new master cylinder would be any different?
I am all for new parts but figure out your problem first otherwise you may have the same problem just with new parts and a lighter wallet.
The key to any good repair is the proper diagnosis