ABS/ESP ITT Mark 20
ABS/ESP ITT Mark 20, bleeding brake system
WARNING:
^ Do not under any circumstances allow brake fluid to come into contact with liquids which contain mineral oils (e.g. oil, grease, cleaning agents). Mineral oils damage the plugs and seals in the brake system.
^ Brake fluid is poisonous and must not under any circumstances be siphoned through a tube using the mouth. Because of its caustic properties it must not come into contact with paintwork.
^ Brake fluid is hydroscopic, i.e. it absorbs moisture from the surrounding air, and should always be stored in airtight containers.
^ Always observe the relevant environmental regulations for disposal.
System must first be pre-bled when one chamber in the brake fluid reservoir is completely empty (e g brake system leaking).
Afterward the hydraulic unit must be bled with vehicle diagnostic, testing and information system VAS 5051 in function "04. Basic setting".
When using a brake filler and bleeder unit (such as VAS 5234) to replenish the brake fluid, make sure that filling pressure does not exceed 1 bar.
If the filling pressure exceeds 1 bar, a hydraulically controlled change-over valve (which is required for the EDL function) prevents unrestricted flushing of the EDL related parts of the hydraulic unit. If this is the case, it may not be possible to bleed the system properly.
For this reason the brake fluid pressure must be reduced to 1 bar on the brake filling and bleeding appliance
,Refer to Operating instructions for VAS 5234
Note:
^ Use only new brake fluid with part No. B COO 700 A. (Container contents available from O. 25 to 30 litres).
^ Rinse off any brake fluid spillages using plenty of water.
Brake filler and bleeder unit VAS 5234, bleeding brake system
Special tools and equipment
^ Brake filler and bleeder unit VAS 5234
Work sequence
^ Connect brake filler and bleeder unit VAS 5234.
^ Remove protective cap from bleeder screw on brake caliper and attach bleeder bottle hose to bleeder screw.
Bleeding sequence
1. Left front brake caliper
2. Right front brake caliper
3. Left rear brake caliper
4. Right rear brake caliper
^ Leave bleeder screw open, with bleeder bottle hose connected, until brake fluid emerges out of the bleeder screw clear and free from air bubbles.
^ Build up pressure in brake system to aid bleeding by pumping pedal five times.
^ Tighten bleeder screw to 10 Nm. Detach hose and install protective cap on bleeder screw.
^ Repeat procedure on remaining brake calipers in the specified bleeding sequence.
^ Top off fluid level in reservoir to "MAX" mark (according to degree of pad wear) and close reservoir cap.
^ Start engine and test pedal travel and pedal pressure.
^ If the pedal travel is excessive, check brake system for leaks or repeat bleeding procedure.
A test drive must be carried out after bleeding brakes. When doing this an ABS-controlled brake application on all four wheels must be performed at least once.
Changing brake fluid
Refer to Maintenance booklet
Bleeding brake system without brake filling and bleeding appliance
Note: Make sure there is always sufficient brake fluid in the reservoir.
^ Remove protective cap from bleeder screw on brake caliper and attach bleeder bottle hose to bleeder screw.
^ Refer to Bleeding sequence
^ Build-up brake pressure in brake system by pumping the brake pedal.
Note: Pump the pedal slowly to ensure bubble-free flow.
^ Hold brake pedal down after building up pressure.
^ Open bleeder screw with bleeder bottle hose attached until pressure drops (pedal drops).
^ With brake pedal held down, close bleeder screw.
^ Release brake pedal and wait for approximately 2 seconds to enable brake fluid to run from brake fluid reservoir.
^ Repeat operation until brake fluid emerges clear and free from air bubbles.
^ Tighten bleeder screw to 10 Nm, detach bleed hose and install protective cap on bleeder screw.
^ Repeat procedure at the remaining brake calipers in the specified bleeding sequence.
Note:
^ If one chamber of brake fluid reservoir has run completely empty (e.g. due to leak in brake system), brake system must be pre-bled.
^ Top off fluid level in reservoir to "Max" mark (according to degree of pad wear) and close reservoir cap.
^ Start engine and check pedal travel and brake pedal pressure.
^ If the pedal travel is excessive, check brake system for leaks or repeat bleeding procedure.
Changing brake fluid
Refer to Maintenance booklet
Brake fluid reservoir is empty, bleeding brake system
Special tools and equipment
^ Brake filler and bleeder unit VAS 5234
^ Vehicle diagnostic, testing and information system VAS 5051 and VAS 5051/1
When using a brake system filling and bleeding appliance (such as VAS 5234) to replenish the brake fluid, make sure that filling pressure does not exceed 1 bar.
If the filling pressure exceeds 1 bar, a hydraulically controlled change-over valve (which is required for the EDL function) prevents unrestricted flushing of the EDL related parts of the hydraulic unit. If this is the case, it may not be possible to bleed the system properly.
For this reason the brake fluid pressure must be reduced to 1 bar on the brake filler and bleeding unit
Refer to Operating instructions for VAS 5234.
Filler and bleeder unit V.A.G 1238/B is not suitable for bleeding the brake system by using the "Basic setting" function.
If only filler and bleeder unit V A G 1238/B is available, then switch unit on/off to ensure that sufficient brake fluid is always present in reservoir
Requirement for test:
^ Connect vehicle diagnostic, testing and information system VAS 5051, select "Vehicle self-diagnosis" and vehicle system "03. Brake electronics".
Pre-bleeding of brake system
^ Connect brake filler and bleeder unit VAS 5234.
^ Open bleeder screws in the specified sequence and pre-bleed brake calipers.
1. Bleed left front and right front brake calipers simultaneously.
2. Bleed left rear and right rear brake calipers simultaneously.
^ Leave the bleeder screw open, with brake fluid hose connected, until brake fluid free from air bubbles comes out of the bleeder screw.
Bleeding
Display on VAS 5051:
^ Select the diagnosis function "04. Basic settings" from the menu -1-.
Note: During the next steps the ABS warning lamp flashes.
Display on VAS 5051:
1. Enter display group
^ Using the keypad -2-, enter "001" to select Display group 001 and confirm entry with Q key.
Display on VAS 5051:
1. System in basic setting
2. Display group 1
3. Press pedal and hold in position
- Operate pedal with substantial foot pressure and hold.
^ Pedal drops, hydraulic pump starts up, pedal returns
Display on VAS 5051:
3. Release pedal; FR/FL bleed screws OPEN <>
- Release pedal, open front bleeder screws.
- Press the (arrow) button to advance to Display group 002.
Display on VAS 5051:
1. System in basic setting
2. Display group 2
3. Please wait (10 sec.)
- Wait for 10 seconds.
^ Hydraulic pump starts up briefly
Display on VAS 5051:
3. Press pedal 1 0X; bleed screws CLOSED <>
- Press pedal 10 times, close front bleed screws.
- Press the (arrow) button to advance to display group 003.
Display on VAS 5051:
1. System in basic setting
2. Display group 3
3. Press pedal and hold in position ...
^ Repeat bleeding procedure as described above
^ Press the (arrow) button several times to advance to the next display groups until display group 17 is indicated.
Display on VAS 5051:
1. System in basic setting
2. Display group 17
3. Partial bleeding over...
^ Press the (arrow) button to exit from diagnosis function "04. Basic settings".
Display on VAS 5051:
^ Select diagnosis function "06. End output" from the menu -1-.
Display on VAS 5051:
^ When this display appears, switch off ignition and unplug diagnostic connector.
^ Now perform bleeding of brake system.