BMW 3 Series Service Manual (E39)

300-12

ISus~ension,Steerincl and Brakes - General

ABS system

The electronically controlled ABS maintains vehicle stability and control during emergency braking by preventing wheel lock-up. ABS provides optimum deceleration and stability during adverse conditions. It automatically adjusts brake system hydraulic pressure at each wheel to prevent wheel lock-up.

Automatic Stability Control (ASC)

NOJE-

ASC (Automatic Stability Control) may also be referred to as A S C i T (Automatic Stability ControkTraction).

A S C works in conjunction with ABS and the engine management system to enhance vehicle control. The main function of the A S C system is to maintain the contact between the tires and the road surface under all driving conditions. This is achieved through exact application and management of braking and drivetrain forces.

The A S C system improves traction by electronically applying the rear brakes when the rear drive wheels are spinning at a faster rate than the front wheels. The combined ABSIASC control module, operating through the ABS hydraulic control unit, modulates braking force at the rear wheels.

In addition, A S C overrides the throttle opening to reduce engine torque and maintain vehicle traction. Because the throttle is controlled electronically, the driver cannot increase engine power output during AS C intervention regardless of how far the accelerator pedal is pushed.

300-14

ISusoension. Steerina and Brakes - General

Dynamic Stability Control (DSC)

NOTE-

Airsupply pump is located beneath a cover under the spare tire in the floor of the cargo compartment.

-If ride height is outside specification listed, install new springs. Suspension spring removal and installation is covered in 310 Front Suspension and 330 Rear Suspension.

310 Front Suspension

31 0-2

IFront Suspension

This repair group covers the repair and replacement of components that make up the front suspension of E39 cars.

Two different types of steering systems are used in the E39 series. 6-cylinder (5251,5281and 530i) models are equipped with a rack and pinion type steering system mounted to an aluminum subframe. V-8 (540i)models use a steering gearbox type system mounted to a steel subframe.

See 300 Suspension, Steering and Brakes-General for a description of the front suspension and components, as well as specifications for setting ride height.

CAUTION-

Some E39 models are equipped with aluminum suspension components. The foiiowing cautions apply:

Due to the chemical and corrosion characteristics of aluminum, do not bring into contact with battery acid.

* Do not clean with wire brushes with brass or iron bristies. Only use brushes with stainless steei bristles.

Do not expose to flying sparks from grinding/cutting operations.

* Do not subject to steei welding splashes.

Do not expose to temperatures over 80°C (176°F). even for short periods. Temperatures in painting faciiities are not a problem.

Special tools

Special service tools are required for most of the work described in this repair group. In addition to the tools depicted in the illustrations,avariety of press tools are necessaryfor control arm bushing replacement. Read the procedures through before beginning any job.