Description & Operation

Liberty and Wrangler are equipped with standard front disc and rear drum brake system. Grand Cherokee is equipped with a 4-wheel disc brake system. Anti-Lock Brake System (ABS) is optional on Liberty and Wrangler, and standard on Grand Cherokee. See appropriate ANTI-LOCK article.

All models use a floating caliper disc brake assembly on the front. Grand Cherokee uses a double-piston caliper on the front and a single piston caliper on the rear. All other models use a single piston caliper on the front. On all models, as brake pedal is depressed, hydraulic pressure passes through a proportioning valve to brake caliper piston. This force is transmitted to inboard brake pad, forcing it against braking surface of rotor. Pressure then moves outer caliper housing and pad inward on caliper mounting bolts, forcing outer pad against outer braking surface of rotor.

All models use ventilated disc brake rotors on the front. On Liberty and Wrangler, cast brake drums are used on the rear. On Grand Cherokee, solid rotors are used on the rear. A brake drum is cast into the middle of rotor for parking brake.

Liberty and Wrangler use a combination valve containing a rear brake proportioning valve and a pressure differential switch. Proportioning valve operates by restricting hydraulic pressure to rear brakes at a given ratio when system hydraulic pressure reaches a certain point. This improves front-to-rear brake balance during high speed braking, when a percentage of rear weight is transferred to front wheels. Valve reduces rear brake pressure and delays rear wheel skid. On light brake application, valve allows full hydraulic pressure to rear brakes. Proportioning valve is not serviceable and must be replaced if faulty.

Grand Cherokee uses an Electronic Brake Distribution (EBD) system which functions like rear proportioning valve. EBD uses ABS to control slip of rear wheels in partial braking range. The braking force of rear wheels is controlled electronically by using the inlet and outlet valves located in the Hydraulic Control Unit (HCU).

Two brake warning lights may be used. A Red BRAKE warning light is in circuit with pressure differential (brake warning) switch and parking brake switch. Red BRAKE warning light will come on for 2-3 seconds during start-up as a bulb check, when parking brake is applied or when there is a pressure differential between front and rear brakes indicating a system leak. On models equipped with ABS, an Amber ABS light is used. Amber ABS light will come on for 2-3 seconds during start-up as a bulb check and when an ABS fault occurs.

Parking brake system on Liberty and Wrangler uses a cable mechanism to actuate standard rear brakes for parking or emergency service. Parking brake system on Grand Cherokee uses cable actuated dual brake shoes secured to backing plate. Parking brake drum is cast into rear disc brake rotor.