Hydraulic Control Assembly - Antilock Brakes: Service and Repair

Hydraulic unit, replacing

Note! As the illustrations in this service information are used for different model years and/or models, some variation may occur. However, the essential information in the illustrations is always correct.

Preparation
Remove the battery lead. See Battery, disconnecting Battery Disconnecting

Warning! The hydraulic unit must not be opened under any circumstances. Reassembling it requires special equipment and facilities.

Note! An hydraulic unit for ABS has only eight valves while a unit for ABS and STC (stability and traction control) has ten valves. The method for replacing the unit is the same for both types. Check thoroughly when installing the new unit that the unit is the correct type.




Secure the pedal in the depressed position.
Use a pedal jack.
Remove the protective cap from the bleed nipple at the left front wheel.
Install a plastic hose on the nipple. Open the bleed nipple.
Collect the brake fluid in a container (bottle).
Shut the bleed nipple.

Removing the brake pipe for the master cylinder/ABS unit
Remove the brake pipe between the master cylinder and the ABS hydraulic modulator. See Brake pipe master cylinder/ABS unit, replacing Brake Pipe Master Cylinder/ABS Unit, Replacing

Removing the ABS hydraulic modulator




Disconnect the brake pipes to the wheel brakes from the ABS hydraulic modulator.

Note! Note the position of the pipes in the hydraulic unit.

Hang the brake pipes on the cross member.
Plug the brake pipes and connections for the ABS hydraulic modulator and master cylinder.
Remove the connector from the control module.
Remove the 3 mounting screws for the bracket by the side member.
Raise the ABS hydraulic modulator and bracket.





Remove:
- the connector for the pump motor from the control module
- the bracket from the ABS hydraulic modulator
- the control module.

Installing the ABS hydraulic modulator





Warning! The ABS hydraulic modulator must not be opened under any circumstances. Reassembling it requires special equipment and facilities.

On the control module check:
- that none of the pins on the connector are damaged
- that there are no contaminants on the mating surfaces between the control module and the ABS hydraulic modulator.

Install:
- the control module on the ABS hydraulic modulator
- the screws. Tighten to 1.8 Nm.

Note! The ABS hydraulic modulator is filled with brake fluid. It is important that the plugs are not removed until the brake pipes are to be connected.





Install:
- the new hydraulic unit on the bracket. Tighten the mounting screws. Tighten to 8 Nm
- the connector for the pump motor to the control module
- the ABS hydraulic modulator and bracket
- the three screws. Tighten to 10 Nm.
Remove the protective plugs. Connect the brake pipes to the wheel brakes. Tighten to 15 Nm.

Installing the brake pipes on the master cylinder/ABS unit

Warning! No ABS, stability and traction control functions are available when there is communication with the Brake control module (BCM) (Volvo Diagnostics are activated). ABS warning lamp flashes for as long as the diagnostics are activated. To cancel the diagnostics before test driving the vehicle, the ignition must be switched off!

Install the brake pipe between the master cylinder and the ABS hydraulic modulator. Then carry out the following. See Brake pipe master cylinder/ABS unit, replacing Brake Pipe Master Cylinder/ABS Unit, Replacing

Note! Remember to remove the pedal jack after installing all brake pipes.