Component Tests: Accumulator

The accumulator, of diaphragm type, is precharged with nitrogen at 80 bar (1160 psi), its function is to store hydraulic energy. If a problem is suspected, following procedure will indicate if precharge pressure has fallen.

1. Depressurize brake system fully.
2. Connect a pressure gauge, capable of reading at least 170 bar (2465 psi), to M10 thread of accumulator after removing bleed screw.
3. Switch ignition on and observe pressure gauge. See Fig 1 .
4. There should be a rapid rise in pressure to accumulator precharged of 80 bar (1160 psi), then a slowing down in rate of increase as pressure rises to system pressure, 170 bar (2465 psi). See graph "A" in Fig 1 .
5. If point x is low as in graph B, i.e. 50 bar (725 psi) it indicates that accumulator has lost its precharge. See Fig 1 .
6. If faulty, fit a new accumulator.

Fig 1: Checking Accumulator Precharge

Courtesy of LAND ROVER NORTH AMERICA, INC.