Brake Master Cylinder: Service and Repair
WM 471519 Removing and installing brake master cylinder
Preliminary work
Remove cross panel -> 508119 Removing and installing cross panel (disassembling plenum panel) - section on "Removing" Service and Repair.
Removing brake master cylinder
Overview
Component overview
Information
If the brake master cylinder is to be replaced, first remove the brake fluid reservoir and then unscrew the fastening nuts for the brake master cylinder (see section entitled "Replacing brake master cylinder").
1. Do not open brake fluid reservoir (to facilitate work).
Information
- In the event of assembly work at the hydraulic connections, all the electric plug connections in the area of the connection point must always be connected. This prevents the inside of the plug connections from being splashed with brake fluid or water.
- Clean any plug connections that have become dirty or damp during removal or fitting with a lint-free cloth.
- Brake fluid on electrical contacts (even thinned brake fluid) leads to corrosion and may cause faults in the system.
- Remove any escaping brake fluid immediately; rinse with water and dry thoroughly if necessary.
Information
- Before disconnecting the brake lines, place a clean absorbent cloth underneath.
- Close off brake lines with a suitable plug immediately after disconnecting.
2. Disconnect brake lines -1- ().
Disconnecting brake lines
2.1. Unscrew cap screws -2-.
2.2. Pull brake lines -1- out of the bores.
2.3. Immediately close off brake lines -1- and bores in the brake master cylinder with suitable plugs.
3. On manual transmission: Pull feed hose for clutch master cylinder off the brake fluid reservoir.
4. Release and pull off electric push-on connector -1- ( -arrow- ).
Pulling off connectors
5. Carefully lay wiring harness -2- aside.
6. Screw off fastening nuts -1- for brake master cylinder -2-.
Screwing off fastening nuts
7. Carefully remove brake master cylinder -1- together with brake fluid reservoir -2- out of the brake booster -3-.
Removing brake master cylinder
Replacing master brake cylinder
Information
If the brake master cylinder is to be replaced, first remove the brake fluid reservoir and then unscrew the fastening nuts for the brake master cylinder.
Information
When replacing the brake master cylinder or the brake fluid reservoir, the latter is not repositioned until the brake master cylinder has been installed.
Brake fluid reservoir
1. Remove brake fluid reservoir.
1.1. Place suitable cloths underneath.
1.2. Carefully bend both lugs => Removal of brake fluid reservoir (illustration as example) on the brake fluid reservoir outwards.
1.3. Pull container up and off.
1.4. Wipe up any escaping brake fluid immediately and rinse away the rest with plenty of water.
Removal of brake fluid reservoir (illustration as example)
2. Remove the brake master cylinder.
Installing brake master cylinder
Overview
Component overview
Information
When replacing the brake master cylinder or the brake fluid reservoir, the latter is not repositioned until the brake master cylinder has been installed.
1. The brake master cylinder is installed in reverse order to removal.
2. Observe tightening torques -> 4X00IN Tightening torques for the brake hydraulic system [1][2]Hydraulic System, Brakes.
Subsequent work
1. Install cross panel -> 508119 Removing and installing cross panel (disassembling plenum panel) - section on "Installing" Service and Repair.
2. Change brake fluid -> 470855 Changing brake fluid.