ASR V/ETS hydraulic unit, function - GF42.40-P-4000-02A
Model 129, 140, 170, 202, 208, 210 except 120.08/28
All switching components of the ABS and ASR or ETS systems are combined in the ASR/ETS hydraulic unit (A7/3).
A 2/2-way valve for build-up/hold pressure or hold/release pressure functions is used on each wheel for control. The self-priming high pressure/return pump (p1), integrated in the hydraulic unit (A7/3), supplies pressure to the ASR or ETS. An integrated return pump (p2) is also used to return brake fluid for ABS control. The inlet pipes of the self-priming high pressure/return pump (p1) contain the inlet solenoid valve (y15) in the Bosch model and inlet valve (15) in the Teves model.
The inlet solenoid valve (y15, Bosch model) is opened once pressures of ≤ 60 bar are reached in the rear axle brake calipers during the ASR or ETS pressure build-up phase. It stays open for the time it takes to actuate the solenoid valves (y10 and y12). When pressures of > 60 bar are reached in one of the rear axle brake calipers during ASR or ETS control, the inlet solenoid valve (y15) remains open continuously. In the Teves model, the inlet valve (15) always remains open apart from when the valve is pressurized via the brake pedal with a pressure of > 0.6 bar.
During ASR control, the switchover solenoid valve (y5) locks the rear axle circuit to the brake master cylinder. The valve is also designed to function as a pressure relief valve and opens at approx. 160 bar. The noise of the pulsating brake fluid is reduced by a diaphragm discharge damper (12) and returned to the brake master cylinder.
A muffler (10) is fitted for each brake circuit to reduce delivery noise. During the ABS/ETS/ASR pressure reduction phase the brake fluid flows back to the high-pressure/return pump via the accumulator.