Fig. 121: Identifying ARS Hydraulic Valve Manifold Components
INDEX REFERENCE CHART
The hydraulic valve block is located on the floor plate of the vehicle behind the front right-hand wheel housing level with the front right-hand door. The hydraulic valve block is connected to a carrier plate bolted to the body.
The hydraulic valve block houses the following valves and sensors:
Tandem Pump
Fig. 122: Identifying Tandem Pump Components
INDEX REFERENCE CHART
The hydraulic pumps fitted in this model series were based on a modular design principle. Depending on the engine and equipment specification, a suitably dimensioned hydraulic pump is flange-mounted to the engine in the same installation space.
Decisive equipment features for these tandem pumps:
The hydraulic pump driven by the engine's poly-V belt is, on vehicles with Dynamic Drive, invariably a tandem pump, which consists of a radial-piston pump section for ARS and a vane pump section for the power steering.
Radial-piston pump section of the tandem pump
This radial piston pump has 8 pistons in a single row and is designed for a maximum pressure of 210 bar.
When the engine is idling, the pump speed is approximately 750 RPM. At that speed, the radial piston pump section delivers a minimum fluid flow rate of approximately 5.5 l/min at a pressure of approximately 3 bar.
Consequently an adequate fluid flow rate is guaranteed even at idling speed.
At a pump speed of 1450 RPM, the maximum fluid flow rate is limited to approximately 9 l/min.
New feature
As a CO2 reduction measure when driving in a straight line, the fluid flow rate of the radial piston pump is restricted by a restrictor valve on the intake side, thereby substantially reducing the circulation pressure and, therefore, the engine power used to drive the pump. As a result, active control of the intake restrictor valve makes a positive contribution to the CO2 equation.
The Dynamic Drive and hydraulic power steering share a common fluid reservoir and fluid cooler.