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DRIVING 
 E231 E231 
TRAILER HYDRAULIC BRAKES 
Connect the trailer or semi-trailer hydraulic brakes with the quick coupler marked with 
an arrow. 
The control of the trailer (semi-trailer) hydraulic brakes and the control of the tractor 
brakes ensure synchronized braking effect of both the vehicles. Working pressure is 
enforced by oil supplied from the hydraulic gear-type pump that works permanently.  
The trailer brake control valve is controlled by brake fluid pressure from the main 
brake cylinders depending on force that influences the brake pedal. Upon maximum 
pressing down the brake pedal, pressure on the coupling head should be 12 - 15 
MPa. The trailer brake valve prefers the brake function to the hydraulic function. 
In the event of shocks when you press down the brake pedal, you have to bleed the 
hose from the brake valve to the quick coupling. 
When driving with trailer, the brake pedals should be connected and safe-
guarded with a lock!  
When braking with one brake pedal, the trailer hydraulic brakes are out 
of operation. 
 
CONNECTION AND DISCONNECTION 
OF QUICK COUPLINGS OF THE 
TRAILER HYDRAULIC BRAKES 
When connecting and discon-
necting the quick couplings you 
should be aware of the rest of oil 
that is kept in the quick coupling 
plug or socket. 
To protect environment you have 
to remove the oil residues after 
each disconnection of the quick 
couplings with a textile rag.