Mercedes-Benz E420 Steering Knuckle Replacement Cost

The steering knuckle houses the wheel hub (the wheel is connected to the hub with the lug nuts or bolts) and wheel bearing. On some vehicles, the hub is bolted to the steering knuckle; on others, it is pressed into the knuckle. Attached at the top and bottom of the steering knuckle, by way of the ball joints, are the control arms that allow the suspension to travel up and down. The steering knuckle is turned by the steering system, and it connects through an arm called a tie rod.

The steering knuckle itself does not often fail. It is possible for the knuckle to become damaged if the vehicle is in a crash, or if it encounters a large pothole. It is more likely that the components in and around the steering knuckle - ball joints, bearings, control arm bushings, tie rod ends - are worn. If indeed the steering knuckle is damaged, symptoms might include tires that are excessively worn on the inside and outside edges or the vehicle pulls to one side when driving. A damaged steering knuckle might present during a suspension alignment. The threads with which the brake caliper is connected to the steering knuckle may become damaged at some point during brake system service. If the threads are damaged, the knuckle should be replaced.

Whether or not a vehicle can be driven with issues related to the steering knuckle is dependent upon the specific component that is worn or failing (see individual components for more information: wheel hub, wheel bearing, control arm, tie rod end). The steering knuckle is not often a problem unless it has been damaged. If the threads to which the brake caliper is attached are damaged and the caliper cannot be secured (during brake service), the vehicle should not be driven until the steering knuckle has been replaced.

The steering knuckle should last the lifetime of the vehicle unless it becomes damaged.

Each component related to the steering knuckle wheel hub, bearing, ball joint, control arm, tie rod has its own set of symptoms and is diagnosed individually. The steering knuckle itself, when damaged, might show up as uneven wear on the inside or outside edges of the tires. Damage might also present itself during a suspension alignment. More likely are the related symptoms associated with the steering knuckle: “clunking sound” when going over bumps or in turns, “growling” noise from the suspension when driving, excessive play in the front wheels. Each of these symptoms can be diagnosed during a suspension inspection.

To replace a steering knuckle, a technician will need to lift and support the vehicle and remove the front wheel and tire. The brake caliper and brake hose will need to be detached from the knuckle and suspended out of the way and the brake rotor will be removed. Any electrical wires connected to the knuckle will need to be disconnected. The technician will detach the tie rod end, as well as the upper and lower control arms, and separate them from the steering knuckle. If the vehicle is front-wheel or four-wheel-drive, the axle shaft (“CV shaft” or “half-shaft”) will also have to be disconnected. The steering knuckle is then dislodged from the control arms and slid off the axle shaft. The wheel hub, bearing, and brake dust shield are removed, as is the wheel speed sensor. The new knuckle is then assembled and installed in the vehicle.

RepairPal recommends checking, and replacing if necessary, the wheel hub and bearing at the same time the steering knuckle is replaced. It is also good practice to inspect the tie rod end, ball joints, and control arm bushings. A four wheel alignment is recommended after the steering knuckle has been replaced.

On some vehicles, the wheel hub and bearing are pressed into the steering knuckle. These components can be extremely difficult to remove without causing damage, and they require a hydraulic press to insert them into the new steering knuckle. It may be necessary to replace the hub and bearing along with the steering knuckle. Also, it is necessary to safely lift and support the vehicle off the ground using a hoist or a jack and jack stands. Failure to do so in a safe manner can result in serious injury.

Replacement of a steering knuckle on most vehicles is an advanced DIY repair that requires tools, equipment, and experience necessary to remove pressed hubs and bearings (including snap rings that retain the bearings), and to press the components into the new steering knuckle. The ball joints and tie rod end also need to be separated. The vehicle needs to be safely lifted in the air with a jack and jack stands to perform this repair. If you are not comfortable with these repair procedures, it would be wise to find a professional technician for the job.