Brake Fluid Accumulator: Description and Operation

There are two fluid accumulators in all hydraulic control units, one each for the primary and secondary hydraulic circuits. The fluid accumulators temporarily store brake fluid that is removed from the wheel brakes during an ABS cycle. This fluid is then used by the pump in the valve body to provide build pressure for the brake hydraulic system.

Additionally on vehicles that are equipped with only ABS (non-traction control vehicles) there is a mini accumulator on the secondary hydraulic circuit which protects the master cylinder's seals during an ABS stop. There is also a noise damping chamber on the primary hydraulic circuit.