Master Cylinder, Distribution & G Valves
Underneath the car, below the brake pedal, is an aluminium cover (commonly referred to as the “rat trap”). Above this cover are located the stop lamp switch, the two distribution valves that meter the high pressure fluid to the calipers, the deceleration conscious pressure limiting valve (G valve) that ensures the brakes do not lock on during an emergency stop and the master cylinder which is fed from the reservoir and provides a low pressure back up to the main high pressure system.
The master cylinder was deleted in 1975 (VIN 22117) and the four lower pistons on the rear calipers that the cylinder operated were incorporated into the high pressure system.
Please note that the distribution valves are not a sealed unit. The internal components are subject to very fine tolerances and the valves are designed to leak a small quantity of brake fluid in order to provide adequate lubrication to these components. It is, therefore, to be expected that over a period of time a pool of brake fluid will be visible on the inside of the rat trap cover. Please refer to the workshop manual (TSD2476 or TSD4200) section G13 for further information.