Genuine Mercedes-Benz 300TD Brake Master Cylinder

Mercedes-Benz 300TD Brake Master Cylinder Parts and Q&A

• Master Cylinder
  004-430-39-01
  Q: How to the remove, overhaul, bench bleeding, and install of a Brake Master Cylinder on Mercedes-Benz 300TD?

  A:

  To disassemble the master cylinder, block out the fender and engine compartment areas to guard them against spills of brake fluid, and lay the master cylinder onto some rags or newspapers before disconnecting and plugging in the brake line connections. Disconnect fluid level sensor connector(s) and the wiring on the pressure differential warning switch, where present. In the case of manual transmission models, detach the hydraulic hose of the clutch with the reservoir, detach the two mounting nuts and pull the master cylinder out of the vacuum booster unit. To do an overhaul, purchase a rebuild kit and arm yourself with a plastic sleeve assembly tool to make the job of fitting the pistons much easier. Wipe the master cylinder outer, extract the sealing ring and pull off the fluid reservoir and sealing plugs. Take the stop screw and seal out by partially depressing the main piston, then withdraw the main piston and all parts. To take out the secondary piston and spring assembly, unscrew the pressure differential warning switch, make sure to clean all the bits and analyze their wear. Replace new seals on the pistons, apply clean brake fluid on the bore and submerge the piston assemblies in brake fluid. When and only when an assembly sleeve tool is used, the pistons are fitted into the sleeve and it is placed in the bore; otherwise, the pistons should be carefully inserted. Fit the secondary sleeves, vacuum sleeves, interring ring and stop washers in place using a circlip screwdriver. Close stop screw with new seal, clean strainer and put back reservoir. Install the pressure smart warning switch wiring, fit and screw the oil lines and screw on the low fluid smart wiring. In the case of bench bleeding the master cylinder is first mounted in a vise, brake line outlets are filled with threaded plugs, the reservoirs filled with brake fluid followed by pushing out the piston assembly changing the plugs to avoid air reentry. Repeat until all brake fluid has drained out and cover the hole with a finger can be another option. Installation will require the installation of a new O-ring on the vacuum booster unit, master cylinder placement and the nuts must be tightened to the recommended torque. Install the fluid plumbing and electrical connections, verify the fluid level sensor, bleed the gear-box hydraulic system in a mechanical transmission model, and reload the warning indicator of pressure difference if fitted and bleed the brakes in all.