Mercedes-Benz 420SEL Suspension Control Arm Bushings Replacement Cost

A technician may diagnose a worn lower control arm bushing during a test drive of the vehicle. The condition may also present itself during a bounce test, where the technician will press down firmly on one corner of the front end of the vehicle to bounce the suspension and pivot the control arms. A severely worn control arm bushing may also show up during a four-wheel suspension alignment since the control arm determines the position and angle of the wheel.

The car must be lifted, and the wheel and tire removed. The lower control arm must be disconnected from the lower ball joint and the vehicle frame or body. An upper control arm is disconnected from the strut tower on the body and from the top of the steering knuckle. It's common to replace related components, such as ball joints, tie rod ends and sway bar links, at the same time a control arm or bushing is replaced.

RepairPal recommends inspecting (and replacing if necessary) the ball joint at the same time that the control arm bushings are replaced. Since the control arm determines the position of the wheel and tire, a wheel alignment is also recommended.

Rubber bushings are adversely affected by heat, grease and oil. It is important to have the bushings periodically inspected to make sure they are free from grease or oil. 

Replacing control arm bushings is generally an intermediate DIY repair. On some vehicles, the control arms come with the bushings already installed. On other vehicles, the bushings need to be pressed into their housings on the control arm before installation. In this case, the repair will be more difficult. However, if you don't have the equipment needed to lift the vehicle, this job should be left to a professional mechanic.