Brake Fluid Accumulator: Description and Operation
HCU BRAKE FLUID ACCUMULATORS AND NOISE DAMPING CHAMBERThere are two brake fluid accumulators in the Hydraulic Control Unit (HCU). There is one brake fluid accumulator for the primary and secondary hydraulic circuits. The brake fluid accumulators temporarily store brake fluid that is decayed from the wheel brakes during an ABS cycle. This stored brake fluid is then used by the pump in the HCU 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 brake fluid 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.
On ABS equipped vehicles with traction control, in addition to the brake fluid accumulators there are also two noise damping chambers in the HCU.