Under normal driving conditions, the abs system functions the same as a standard brake system. The primary difference is that the power assist for normal braking is provided by the booster portion of the hydraulic unit through the use of pressurized brake fluid.
If a wheel locking tendency is noted during a brake application, the abs system will modulate hydraulic pressure in the individual wheel circuits to prevent any wheel from locking. A separate hydraulic line and 2 specific solenoid valves are provided for each front wheel; both rear wheels share a set of solenoid valves and a single pipe from the master cylinder to the proportioner valve or tee. The proportioner valve splits the right and left rear brake circuits to the wheels.
The abs system can increase, decrease or hold pressure in each hydraulic circuit depending on signals from the wheel speed sensors and the electronic brake control module.
During an abs stop, a slight bump or a kick-back will be felt in the brake pedal. This bump will be followed by a series of short pulsations which occur in rapid succession. The brake pedal pulsations will continue until there is no longer a need for the anti-lock function or until the vehicle is stopped. A slight ticking or popping noise may be heard during brake applications with anti-lock. This noise is normal and indicates that the anti-lock system is being used.
During anti-lock stops on dry pavement, the tires may make intermittent chirping noises as they approach lock-up. These noises are considered normal as long as the wheel does not truly lock or skid. When the anti-lock system is being used, the brake pedal may rise even as the brakes are being applied. This is normal. Maintaining a constant force on the pedal will provide the shortest stopping distance.
Vehicles equipped with the Anti-lock Brake System may be stopped by applying normal force to the brake pedal. Although there is no need to push the brake pedal beyond the point where it stops or holds the vehicle, applying more force causes the pedal to travel toward the floor. This extra brake travel is normal.
There are two types of anti-lock brake systems used on these cars. A high pressure Teves ii system is used on 1990 cars. This system is under extreme high pressure and must be serviced carefully. From 1991-93, the Teves iv system is used. The Teves iv system is a low pressure system, and most brake service is the same as vehicles without abs. Refer to the proper anti-lock brake section in this guide to service your car if it is equipped with anti-lock brakes.