Thanks grober.
For anyone else in a similar scenario this might help thanks to "Mike D" from the
www.mercedesshop.com forum.
A new or rebuilt master cylinder, a large bottle of brake fluid, the proper size "flare" or line wrench, a wrench or socket set to fit the mounting nuts, a medium flat shank screwdriver and possibly a larger flat screwdriver or prybar.
Against my better judgement I will tell you how to do it. If at anytime you do not understand these instructions or feel uncomfortable about any of the steps, PLEASE do not attempt it! I have worked as a professional mechanic since 1973 and I can tell you stories about "do-it-yourself" brake jobs which would make you afraid to drive on the roads.
First, compare your replacement cylinder with the old.
The only glitch might be the master cylinder you purchase will not have the plastic resevoir and you need to pull it from your old one. This all depends on the supplier. Some have it and some don't.
If the replacement does not have the jug, place a small tray beneath the lines where they connect to the master cylinder. Remove the brake lines on the side of the master cylinder with the line wrench. Drape a shop towel or rag over the master cylinder/line connections.
Use the medium screwdriver to remove the electrical connections to the screw on lids. Lay them or it aside.
Without the engine running, slowly depress the brake pedal and release the fluid until it is below the plastic jug. You will need to press 3 or 4 times.
The plastic jug just sits in two rubber grommets and will come out with a little judicious wiggling and prying. If you have room, do this while it is still mounted. If not then you can mount the removed master cylinder in a vise and pull the jug. Drain and clean the jug. I prefer to use hot soapy water and blow-dry it with an air compressor but a rag and sunlight works just as well. Lube the nipples with fresh brake fluid or a LITTLE bit of petroleum jelly or silicone lube and slip into the grommets of the new cylinder.
Remove the rag and tray. Wipe dry ALL the brake fluid which you spilled on the fender well. Give it a generous spray of degreaser, 409 or whatever to neutralize the brake fluid.
Remove the two nuts on the back flange of the master cylinder where it connects to the vacuum booster (the big drum looking thingie). Wiggle and tug, the cylinder will slide forward and lift it out. Clean the receptacle where the master cylinder sits in the booster with degreaser or a silicone spray and a rag. Give those mounting studs a good wiping and perhaps a little dab of "never-seize".
Fill the new cylinder with fresh brake fluid. "Bench bleed" the cylinder. Slip the cylinder onto the mounting studs, replace the nuts and tighten. Replace the brake lines loosely. "Snug" the lines. Replace the drip tray. Loosen each line 1/2 to 3/4 turn. Have an assistant SLOWLY depress the brake pedal to the floor and hold. Tighten the lines, have your helper let up on the pedal, count to 10, loosen the lines and have your helper repeat the depress and hold. Do this until you are getting ONLY fresh fluid NOT "bubbly air mixed" fluid (usually only takes once or twice).
Tighten the lines securely, replace the electrical lines remove tray, clean spilled fluid and then "gravity bleed" the entire system.
Gravity bleeding is easy. Top off the cylinder, open the left front caliper bleeder, sit down, have a cold one, keep the fluid topped and wait until you have fresh clean fluid coming from the bleeder. Close the bleeder and repeat on the right front, left rear and right rear. Reverse order on a RHD vehicle (it has to do with doing the shortest lines first).
Done.
You should flush the entire brake system since it may have lots of little rubber particles from the old master cylinder.
