The brakes of a Series Land Rover are not particularly known for their efficiency compared to more contemporary 4x4's. It is inevitable that they will require regular periodic servicing to maximise their effectiveness.
A 'soft' or 'spongy' brake pedal is usually an indicator of air bubbles in the brake fluid, and the remedy for this is well known. But if the brake pedal is firm when the vehicle is either stationary or at the start of a journey and then becomes less firm as the brakes are used repeatedly, then the brake fluid itself could be the cause.
The brake fluid is a liquid which naturally absorbs water vapour from the air and this lowers the boiling point of the fluid. The brake cylinders of a Series Land Rover become hot as the brakes are repeatedly used and the heat generated is transfered to the brake fluid. If the fluid boils and water vapour/steam is formed, then this, unlike the lquid, can be squashed and this is the cause of the loss of brake pedal firmness. As the fluid cools down then the water vapour/steam condenses back to liquid and firmness of the brake pedal can be expected to return.
Since more water vapour is gradually absorbed over time it is generally recommended to change the brake/clutch fluid every two years. In a very humid climate or if fording is frequently undertaken then it may be necessary to change it more frequently. It is important that the screw tops of the brake and clutch reservoirs be fully tightened to reduce exposure of the fluid to the air.
is graded by its boiling point by giving it a DOT number (US Department Of Transportation number). DOT 3 fluid boils at approx 200C when new and this drops to approx 140C as some water vapour is absorbed. DOT 4 has equivalent boiling points of 230C and 155C respectively. DOT 3 is recommended for the drum brakes of the Series Land Rover and DOT 4 for disc brake applications though it can also be used in the drum brake situation without problem.
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