Citytrac 4200
Citymaster 1200
Citycleaner
Service Documents
For internal use only
Status
March 2009
Page
38 of 108
The high pressure (drive pressure) actuates the valve, whereby a connection of the return flow line to the pump is diverted by an
aperture to the quantity control and via a pressure control valve (16 bar) to the tank. The pressure control valve prevents the feed
pressure dropping below 16 bar.
The feed pressure controlled at 22 bar for controlling the switching valve (front/all-wheel drive) and controlling the differential valve is
extracted at connection G on the hydraulic pump.
When rear-wheel drive is switched off, the all-wheel drive valve establishes a connection to the flow and return flow of the wheel
motors to compensate for loss of oil through leakage. When this switch position is set, the feed pressure is approx. 1 – 2 bar lower,
depending on the tolerance and wear of the motors.
In the event of wheel or motor damage evident due to high oil loss, the feed pressure may drop until a functional fault occurs in the
respective system.
In the case of too low a feed pressure and high pressure:
1. Check the towing aid (bypass) for signs of leaks.
2. Check the flush valve for impermissible leaks.
3. Check the wheel motors for impermissible losses due to oil leakage (max. 2.5 l/min per engine at max. speed).
