Brake Fluid Accumulator: Service and Repair

ACCUMULATOR
Service repair no - 70.65.21

WARNING: The accumulator is precharged with nitrogen at a pressure of up to 80 bar (1160 inch lbs.). Handle with extreme caution. DO NOT puncture or burn if disposal is necessary.


Remove
1. Disconnect battery negative lead.
2. Depressurize system.
3. Position cloth beneath accumulator to catch any fluid spillage.





4. Remove accumulator. Discard O-ring.


Disposal

WARNING: It is essential that safety goggles are worn when carrying out this procedure.

5. Secure accumulator firmly in a suitable vice.
6. Drill 5mm hole in top of accumulator to depressurize nitrogen chamber.
7. Dispose of accumulator in an approved manner


Refit
8. Using a new O-ring, fit accumulator to pump.
9. Reconnect battery negative lead.
10. Bleed braking system.


ACCUMULATOR PRECHARGE-CHECK
The diaphragm type accumulator is precharged with nitrogen at 80 bar (1160 inch lbs.), its function is to store hydraulic energy. Over a period of years, a normal loss of precharge will occur. This procedure will indicate the extent to which precharge pressure has fallen.

NOTE: A new accumulator at 20°C has a A nominal pressure of 80 bar (1160 inch lbs.). Minimum acceptable pressure is 50 bar (725 inch lbs.).

1. Depressurize braking system.
2. Remove 3 nuts securing pump/motor assembly to valance. Raise assembly from mounting to allow clearance for pressure test adaptor.





3. Remove banjo bolt securing high pressure hose to pump. Collect sealing washers.
4. Connect pressure gauge to pump using LRT-70-003 through high pressure hose union.

NOTE: Use original sealing washers.

5. Switch ignition on. Observe pressure gauge.





6. Pressure will rapidly rise to the accumulator precharge value, point X, at which point rate of increase will reduce as pressure rises to system pressure of approximately 170 bar - see graph "A".
7. With a new accumulator, point "X" will occur at 80 bar.
8. Renew accumulator if point "X" occurs below 50 bar.
9. Depressurize system. Remove test equipment.
10. Using new sealing washers, position high pressure hose to pump. Secure with banjo bolt. Tighten to 24 Nm (18 ft. lbs.)
11. Align pump/motor assembly to mounting. Secure with nuts. Tighten to 8 Nm (6 ft. lbs.)
12. Bleed brake system.