Venting DSC8 and venting the control lines; E83 RL

The described procedure is compulsory for the E83 R L due to the line arrangement between tandem-brake master cylinder and DSC unit. This brake venting procedure can also be carried out in the event of problems with venting the brake system on the E83 LL and E60.

Control lines: The so-called control lines (connecting leads between tandem-brake master cylinder and DSC unit) on the E83 RL cannot be bled in the conventional manner using the brake fluid replacement device. The cause of this is the large line diameters and the line arrangement. With this special venting routine, brake fluid and enclosed air are pushed towards the brake calliper.

Primary circuit: In the DSC unit, air bubbles can stick to the edges and valves. The vibrations that occur during venting with the DIS tester /GT1 loosen the air bubbles.

Secondary circuit: Normally (DSC not active), the secondary circuit of the DSC unit is closed. Air contained in it cannot escape during venting with the brake fluid replacement device. The pump and inlet/outlet and high-pressure switch valves are activated using the DIS Tester / GT1. This also vents the secondary circuit.

Following replacement and repair of the following parts, the DIS tester /GT1 must be used for venting:

• Hydraulic unit
  
• Master brake cylinder
  
• Components and/or connecting lines located between the hydraulic control unit and master brake cylinder
  

Operations:

The order of the operation must be adhered to without fail: rear left (RL), front left (FL) front right (FR) rear right (RR)

1. Connect the brake fluid replacement device and switch online;(The fill pressure must not exceed 2 bar)
   
2. Vent control line of rear axle brake circuit:
   
   • Attach the venting bottle to the RL vent valve
     
   • Open the RL vent valve
     
   • Start the brake venting procedure (inspection step: ”Vent rear axle brake circuit”)
     Caution: do not press the brake pedal!
     
3. Vent RL brake hose:
   
   • The RL vent valve remains open
     
   • Continue brake venting procedure (inspection step: ”Vent RL brake hose”)
     
   • Pump the brake pedal while the routine is running: - Press the brake pedal firmly as far as it will go - Hold the brake pedal for 4 to 5 seconds - Let go of the brake pedal
     Approx. 6 pump operations in 30 seconds. Finish the pump operation when bubble-free brake fluid flows out. If necessary, continue pressing the brake pedal, i.e. more than 6 operations and longer than 30 seconds
     Note: brake pedal resistance changes depending on the valve switching operations and the running pump. The brake pedal is still to be operated as described.
     
   • Close the RL vent valve
     
4. Vent control line of front axle brake circuit:
   
   • Attach the venting bottle to the FL vent valve
     
   • Open the FL vent valve
     
   • Continue brake venting procedure (inspection step: ”Vent front axle brake circuit”)
     Caution: do not press the brake pedal!
     
5. Vent FL brake hose:
   
   • The FL vent valve remains open
     
   • Continue brake venting procedure (inspection step: ”Vent FL brake hose”)
     
   • Pump the brake pedal while the routine is running: - Press the brake pedal firmly as far as it will go - Hold the brake pedal for 4 to 5 seconds - Let go of the brake pedal
     Approx. 6 pump operations in 30 seconds. Finish the pump operation when bubble-free brake fluid flows out.
     
   • Close the FL vent valve
     
6. Vent FR brake hose:
   
   • Attach the venting bottle to the FR vent valve
     
   • Open the FR vent valve
     
   • Continue brake venting procedure (inspection step: ”Vent FR brake hose”)
     
   • Pump the brake pedal while the routine is running: - Press the brake pedal firmly as far as it will go - Hold the brake pedal for 4 to 5 seconds - Let go of the brake pedal
     Approx. 20 pump operations in 100 seconds. Finish the pump operation when bubble-free brake fluid flows out.
     
   • Close the FR vent valve
     
7. Vent RR brake hose:
   
   • Attach the venting bottle to the RR vent valve
     
   • Open the RR vent valve
     
   • Continue brake venting procedure (inspection step: ”Vent RR brake hose”)
     
   • Pump the brake pedal while the routine is running: - Press the brake pedal firmly as far as it will go - Hold the brake pedal for 4 to 5 seconds - Let go of the brake pedal
     Approx. 20 pump operations in 100 seconds. Finish the pump operation when bubble-free brake fluid flows out.
     
   • Close the RR vent valve
     
   • Switch off ignition, wait 10 seconds, switch ignition on again. This also ensures that the activation routines are terminated.
     
8. Remove the brake fluid replacement device
   

Note:

A second person is required for this task