MG MG6 Series 2011 Service Manual page 616

Brake System
Master Master Master Cylinder Cylinder Cylinder Assembly Assembly Assembly
1. Secondary pressure chamber
2. Secondary piston
3. Secondary feed hole
4. Fluid reservoir ports
5. Master cylinder
6. Primary feed hole
7. Primary centre valve
The master cylinder assembly produces hydraulic pressure to
operate the brakes when the brake pedal is pressed.
The assembly is attached to the front of the brake servo
assembly, and typically comprises a cylinder containing two
pistons in tandem.
The rear piston produces pressure for the primary circuit and
the front piston produces pressure for the secondary circuit.
A brake fluid reservoir is installed on top of the cylinder.
The reservoir is internally divided to provide an independent
supply of fluid to each brake circuit, and so prevent a single fluid
leak from disabling both primary and secondary brake circuits.
Should a failure occur in one circuit, the remaining circuit will
still operate effectively, although brake pedal travel and vehicle
braking distances will increase.
If the fluid level in the reservoir is too low, a level switch
opens and breaks a circuit between the ABS modulator and
the instrument pack, which illuminates the brake warning light.
Version 2.0
8. Primary piston
9. Primary springs
10. Primary pressure chamber
11. Secondary centre valve
12. Valve pin
13. Secondary spring
Front Brakes
The front brakes each comprise of a hub mounted, single
piston, sliding calliper assembly and a ventilated disc.
The inboard side of the disc is protected by a shield.
On the RH brake, a pad wear sensor is connected to the
inboard brake pad and wired in series with the rear brake pad
wear sensor.
The connector of the sensor lead is located on the inner wing
in the engine compartment.
When hydraulic pressure is supplied to the calliper, the piston
extends and forces the inner pad against the disc.
The calliper housing reacts and slides on the guide pins to bring
the outer pad into contact with the disc.
If the brake pads become sufficiently worn, the RH disc causes
the pad wear sensor to go open circuit and illuminates the pad
wear warning light in the instrument pack.
Brake
600