Hydraulic Control Assembly - Antilock Brakes: Service and Repair
Hydraulic modulator, replacementNote: Never open ABS hydraulic modulator under any circumstances. Reassembling it requires special equipment and facilities.
Preparations
^ Ignition off.
^ Place a rag under the ABS hydraulic modulator as protection against brake fluid spillage.
^ Depress the brake pedal a few times so that no vacuum remains in the power brake booster.
^ Clean the brake pipes terminals at the ABS hydraulic modulator and master cylinder.
^ Disconnect the ignition cable from the ignition coil and its mountings on the air cleaner (ACL) housing.
^ Remove Air Cleaner (ACL) housing and air preheating intake pipe.
On cars with turbocharger (TC) engines
Remove:
^ Intake pipe between Air Cleaner (ACL) housing and Turbocharger (TC).
Locking brake pedal
^ Raise the car.
^ Remove protective cap from bleed nipple at left front wheel.
^ Connect hose from collection bottle.
^ Open the bleed nipple and depress the brake pedal. Hold it down or lock the brake pedal in that position.
^ Shut the bleed nipple.
Removing bracket with ABS hydraulic modulator
Remove:
^ Brake pipes between ABS hydraulic modulator and master cylinder.
^ Disconnect brake pipes to wheel brakes. Immediately plug the brake pipes and the ABS hydraulic modulator connectors to prevent dirt entering the turbocharger
^ Disconnect control module connector by pressing in the catch on the rear edge of the cover (wheel arch side). Carefully turn the cover upwards so that the lock catch is released.
Remove:
^ Bracket mounting screws and lift up bracket.
^ Lift up the bracket and disconnect the vacuum hose.
Cars with TRACS
^ Lift up the bracket a little and move forward.
^ Remove check valve with vacuum hose from the power brake booster.
Removing ABS hydraulic modulator from bracket
Note: ABS hydraulic modulator must be replaced as a complete unit. Never open ABS hydraulic modulator under any circumstances. Reassembling it requires special equipment and facilities.
^ Disconnect pump motor connector from control module.
^ Remove bracket and control module from the ABS hydraulic modulator.
Checking ABS hydraulic modulator
^ Check that the ABS hydraulic modulator is of the correct type depending on whether or not the car is equipped with TRACS. The difference is that the TRACS hydraulic modulator has seven valves to the control module instead of six.
Note: Never open ABS hydraulic modulator under any circumstances. Reassembling it requires special equipment and facilities.
Installing ABS hydraulic modulator
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.
^ Check and install control module on the ABS hydraulic modulator according to Replacing control module. Install screws. Tighten to 1.8 Nm (1.33 ft. lbs.).
^ Install the new ABS hydraulic modulator on the bracket and tighten mounting screws. Tighten to 8 Nm (5.90 ft. lbs.).
^ Hold the vacuum hose to one side and carefully install the bracket in the car.
^ Connect the pump motor connector to the control module.
^ Tighten mounting screws to 8 Nm (5.90 ft. lbs.).
Cars with TRACS
Insert the vacuum hose between the bracket and ABS hydraulic modulator. Check that the check valve and rubber seal are intact. Connect the check valve to the power brake booster.
Continued ABS hydraulic modulator installation
^ Connect connector to the control module and pump motor.
^ Remove plugs and connect the brake pipes to the ABS hydraulic modulator and master cylinder. Tighten to 14 Nm (10.33 ft. lbs.).
^ Release the brake pedal.
^ Install air cleaner (ACL) housing with intake pipe and air preheating hose.
^ Connect ignition cable to ignition coil.
On cars with Turbocharger (TC) engines
Install: Intake pipe between Air Cleaner (ACL) and Turbocharger (TC).
Finishing
^ Bleed brake system. Wash away any spilled brake fluid with warm water and car shampoo.
Function test
^ Read off any Diagnostic Trouble Code (DTC)s stored in control module and erase them.
^ Turn off the diagnostic tool. Check that the ABS warning lamp stops flashing.
^ Test drive car, check that brakes work and that ABS warning indicator stops flashing.
Warning: The ABS and EBD functions are not available when Volvo Diagnostics are activated. Great care should be taken when test driving as there is a great risk that the wheels will lock.