Replacing the Master Cylinder

Replacing the master cylinder

Preparations
Clean around brake fluid reservoir cap, by pipe connections, and, if necessary, by hose connection between reservoir and master cylinder to prevent dirt entering braking system.

Caution! Release non-return valve in air hydraulic brake power assist unit (brake servo) or pump brake pedal until it goes hard to avoid any vacuum remaining when undoing the master cylinder. Otherwise, there is a risk that the O-ring acting as a seal will be sucked into the servo and disappear.

Put rags under master cylinder to prevent brake fluid spillage on paint work surfaces.

Note! Do not open the master cylinder under any circumstances. It takes special equipment and facilities to reassemble.

Removing master cylinder
Ignition off.

Remove:
- Brake fluid reservoir as per. Brake fluid reservoir, replacement and cleaning.





Disconnect:
- Connector to EBD sensor from master cylinder.
- Brake pipe from master cylinder.
Plug brake pipe to prevent dirt entering braking system.

Remove:
- Mounting nuts.
- Master cylinder.

Installation, master cylinder.

Check:
- That there is no dirt in the master cylinder connections and that the packing box is intact.

Install:
- Master cylinder and EBD pressure sensor. Use new nuts.Tighten to 25 Nm (18.4 ft.lb).

Remove:
- Plugs from brake pipe and connect brake pipe. Tighten to 14 Nm (10.3 ft.lb).

Connect:
- Connector to EBD sensor.
- Brake fluid reservoir, as per Brake fluid reservoir, replacement and cleaning.

Finishing




- Bleed braking system as per. Bleeding brakes.Then continue as per instructions below.
- Bleed clutch on cars with manual transmission.
Clean off any brake fluid spillages with lukewarm water and car-wash shampoo.

Pressure-testing the braking system




Once the system has been bled, it must be pressure-tested.
Depress the brake pedal as if braking sharply, nearly enough to lock the wheels, for 30 seconds.
Check if there is any brake fluid leaking from the master cylinder.