Figure 290. Removing and installing the master brake cylinder: 1 - brake fluid reservoir cap; 2 - brake fluid reservoir; 3 - master brake cylinder; 4 — union nut of the pipeline, 12–16 N·m; 5 — mounting nut M8, 25–28 N·m; 6 - sealing ring (always subject to replacement); 7 - hydraulic hose; 8 - hose clamp; 9 — liquid level sensor plug
The master brake cylinder is mounted in front of the vacuum booster housing and can be removed from the engine compartment. Figure 290 shows the components of the master cylinder together with the booster. When removing the master brake cylinder, the following operations must be performed:
- unscrew the brake fluid reservoir cap and remove the mesh underneath it by prying it off with a screwdriver;
- disconnect the brake fluid level sensor plug from the brake master cylinder side;
- place one end of the hose on the bleed nipple of one of the front brake mechanisms, and lower the other end into the prepared container. Loosen the nipple and, pressing the brake pedal, pump the fluid out of the system. You can also pump the liquid out of the tank using a bulb syringe, as shown earlier. Place a rag under the cylinder to prevent liquid drops from getting on engine parts;
- clamp the hose leading to the brake fluid reservoir;
- cut the hose clamp with side cutters and remove the hose from the tank;
Figure 291. Removing the brake fluid reservoir
- by loosening the tank fastenings outwards (figure 291), take it off;
- unscrew the pipes from the master brake cylinder and carefully move them to the side. Protect the ends from dirt. Again, be careful not to let any brake fluid drip onto any parts in the engine compartment. When assembling, tighten the union nuts of the pipelines with a torque of 12-16 N·m;
- unscrew the cylinder and remove it, tilting it away from the push rod. Make sure that the cylinder does not turn over and the piston rod does not come out of its seat. Remove the sealing ring located behind the cylinder.
(Publication taken from an online resource: MercedesMan.ru)
Installation must be carried out in reverse order. The sealing ring is always replaced. Tighten the mounting bolts to a torque of 25 Nm. The booster rod does not require special installation in the cylinder. Finally, insert the reservoir, pour brake fluid into the system and bleed it as described below. Brake fluid capacity for mod. 412D is 0.4 l, for other models - 0.3 l.