Brake Bleeding: Service and Repair

34 00 050 Bleeding brake system with DSC

Note:
Read and comply with General Information.

When replacing or repairing, observe the filling and bleeding instructions for the following parts:
1. Tandem brake master cylinder
2. Hydraulic unit DSC3
3. and components/connecting lines which are fitted between these assemblies.
After work has been completed on the precharging pump, only the front-axle brake circuit has to be bled. Activate precharging pump once with Diagnosis and Information System (DIS).
(Brake fluid changer connected to max. 2 bar filling pressure).
After completing work: Carry out final check with DIS under menu item "Service functions".
Contrary to the instructions in the DIS, the bleeding routine must be restarted on each wheel.
A second person is needed to help carry out this work.

Important:
All vehicles with DSC without precharging pumps must be filled with the new DOT4 low-viscosity brake fluid!
All other models can be filled with the same brake fluid.





Connect DIS.
Call up service function "Bleeding ABS/DSC3 Hydraulics".
Connect brake fluid changer to expansion tank and switch on.

Note:
Check relevant Operating Instructions for each device.
Charging pressure should not exceed 2 bar.





Flushing brake system completely
Connect bleeder hose with collecting tray to bleeder valve on rear right brake caliper.
Open bleeder valve and purge until clear, bubble-free brake fluid emerges.
Close bleed valve.
Follow same procedure on rear left, front right and front left wheel brake.





Bleeding rear-axle brake circuit
Connect bleeder hose with collecting tray to bleeder valve on rear right brake caliper.
Close bleeder valve.
Run bleeding routine with DIS with bleeder valve open.
After completing routine, press brake pedal 5 times to floor; clear and bubble-free brake fluid must flow out.
Close bleed valve.
Repeat procedure at rear left.





Bleeding front-axle brake circuit
Connect bleeder hose with collecting tray to bleeder valve on front right brake caliper.
Close bleeder valve.
Run bleeding routine with DIS with bleeder valve open.
After completing routine, press brake pedal 5 times to floor, clear and bubble-free brake fluid must flow out.
Close bleed valve.
Repeat procedure at front left.





Switch off brake fluid changer and remove from expansion tank.
Check brake fluid level.
Close expansion tank.

Note: Pay attention to rubber seal (1) in sealing cap.