The Hydraulic Control Unit (HCU) on 1997-98 Jeep models also has the Controller Antilock Brakes (CAB) unit mounted to it. It serves the same function as the ABS-ECU does on 1995-96 models. The HCU/CAB is removed as an assembly.
Removal & Installation
See Figure 1
A Diagnostic Readout Box (DRB), or the equivalent type of scan tool, is essential to perform the bleeding of the ABS system.
- Disengage the vent hoses and air cleaner cover.
- Loosen the clamp securing the air cleaner hose to the intake manifold and slide the clamp out of the way.
- Remove the air cleaner cover, hose and filter.
- Unfasten the air cleaner housing to panel bolts and nut, then remove the air cleaner housing.
- Disengage the flex lines at the HCU.
- Disengage the HCU solenoid harness from the main harness and the HCU pump motor harness.
- Disengage the brake lines at the lower left side of the HCU.
If removing the HCU only:
- Remove the HCU solenoid by squeezing the connector fasteners with needle nose pliers then pulling them out of the bracket.
- Unfasten the shoulder bolts attaching HCU to the bracket and remove the HCU.
If removing the HCU and bracket:
- Unfasten the fasteners retaining the HCU to the bracket and remove the HCU.
If only the HCU was removed:
- Install the HCU in the bracket and tighten the shoulder bolts.
- Install the HCU solenoid by pressing the connector fasteners into the bracket.
If installing the HCU and bracket as an assembly:
- Install the bracket on the studs and tighten the fasteners to 92-112 inch lbs. (10-13 Nm).
- Engage the HCU pump motor and solenoid harnesses.
- Start the brake line fittings into the HCU by hand to avoid cross-threading and then tighten the fittings until they are snug.
- Start the flex line fittings into the HCU by hand to avoid cross-threading and then tighten the fittings until they are snug.
- Bleed the brake system. Refer to the proper procedure in this section.
- Tighten the brake line fittings to 130-160 inch lbs. (15-18 Nm) at the HCU and master cylinder, and 160-210 inch lbs. (18-24 Nm) at the combination valve.
- Install the air cleaner assembly, hoses and vacuum lines to the manifold.
- Check the brake pedal action before moving the vehicle and bleed the brakes again if the pedal is not firm, (soft or spongy).
- Test drive the vehicle and verify proper brake operation.