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Rear Shock Absorber Replacement
 
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Pelican Technical Article:

Rear Shock Absorber Replacement

Kerry Jonsson

Time:

4 hours4 hrs

Tab:

$400

Talent:

***

Tools:

T40 Torx socket, E14 Torx external socket, 16mm wrenches and sockets with ratchet, pick, vise grip, door panel removal tool, diagonal pliers

Applicable Models:

Mercedes-Benz W211 (2003-09)

Parts Required:

Rear shock absorber

Hot Tip:

Spray the fasteners with penetrating oil before removing

Performance Gain:

Improve ride by reducing bounce over bumps

Complementary Modification:

Replace the sway bar links if worn

The W211 chassis by Mercedes Benz uses a multiple link rear suspension. Mercedes Benz engineers felt this is the best way to control the angle of the spindle to the road during cornering and going over bumps. If the angle of the spindle changes as the suspension compresses the driver may feel that the car is not stable while cornering. The suspension links are not load bearing members of the suspension. Only the larger lower control arm carries the weight of the car. The rear coil spring is mounted in between the lower control arm and the spring perch on the body. As the spring goes over bumps it compresses as it absorbs the shock. A spring that is under tension wants to return to it original position as soon as it can. When the rear coil spring expands it can slam the wheel back into the ground. This alternating between the rear coil spring absorbing the shock and expanding can lead to the car bouncing up and down and a poor ride. The main job of the rear shock absorber is to slow down the rate of return of the rear coil spring so it does not slam back into the road. This is known as rebound dampening. The rear shock absorber does contribute a small amount to compression dampening but it is not the main job. As a shock absorber wears out it loses the ability to control the rate of the spring return and the wheel will slam into the ground causing bouncing in the rear end. If as you're driving your car you feel the rear end continue to bounce up and down after a few bumps, you probably have worn rear shock absorbers. In this tech article we will go over all the steps to remove the rear shock absorbers.

Lift and support the rear axle of the vehicle. You do not have to remove the tires to perform this job but it does make access much easier since you may not have access to an automotive lift. See our tech article on Jacking and Supporting your Vehicle and Removing the Rear Tires. Be sure to wear safety googles anytime you're working under your vehicle.

The procedure to replace the rear shock absorber is the same for both the left and right side. In these pictures we are working on the left side. Keep in mind all the steps apply to both sides. It is recommended you replace both sides at the same time to keep your handling neutral.

Remember your car may have been serviced before and parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches

This picture illustrates the left side of the trunk by the rear bumper.
Figure 1

This picture illustrates the left side of the trunk by the rear bumper. Using a pick remove the fastener cover from the tie down bracket (green arrow).

This picture illustrates the left side of the trunk up behind the rear seats.
Figure 2

This picture illustrates the left side of the trunk up behind the rear seats. Using a pick remove the fastener cover (green arrow) from the bracket.

This picture illustrates the left side of the trunk by the rear bumper.
Figure 3

This picture illustrates the left side of the trunk by the rear bumper. Using a T40 Torx socket remove the tie down bracket mounting fastener.

This picture illustrates the left side of the trunk up behind the rear seats.
Figure 4

This picture illustrates the left side of the trunk up behind the rear seats. Remove the T40 Torx socket (green arrow)

Remove both tie down brackets from the trunk.
Figure 5

Remove both tie down brackets from the trunk.

This picture illustrates the right side of the trunk at the top of the trunk panel.
Figure 6

This picture illustrates the right side of the trunk at the top of the trunk panel. Remove the two plastic rivets (green arrow). See the following steps for removing the plastic rivets.

Using a door panel removal tool lever out the insert in the plastic rivet.
Figure 7

Using a door panel removal tool lever out the insert in the plastic rivet.

Then lever out the entire plastic rivet.
Figure 8

Then lever out the entire plastic rivet. Do this for both rivets from Picture 6 on the side of the vehicle you are replacing the rear shock absorber on.

This picture illustrates the left side of the trunk.
Figure 9

This picture illustrates the left side of the trunk. Flip the trunk side panel out of the way in the direction of the blue arrows.

This picture illustrates the left side wheel well.
Figure 10

This picture illustrates the left side wheel well. Using a jack, support the lower control arm of the side you are working on.

This picture illustrates the left side of the trunk up behind the rear seats.
Figure 11

This picture illustrates the left side of the trunk up behind the rear seats. Using a 16mm wrench, remove the rear shock absorber upper mounting fastener. You may need to hold the rear shock absorber shaft with a vise grip.

Remove the rear shock absorber upper bushing mount (green arrow).
Figure 12

Remove the rear shock absorber upper bushing mount (green arrow).

This picture illustrates the left side wheel well.
Figure 13

This picture illustrates the left side wheel well. Slowly lower the jack to take the tension off of the rear coil spring. The lower control arm will drop down slightly more than usual.

This picture illustrates looking up at the left side lower control arm.
Figure 14

This picture illustrates looking up at the left side lower control arm. Remove the plastic lower control arm rivets (green arrows).

Remove these plastic rivets as you did the rivets in the trunk.
Figure 15

Remove these plastic rivets as you did the rivets in the trunk. Pull out the center insert from the plastic (green arrow), then pull out the entire plastic rivet (blue arrow).

This picture illustrates looking up at the left side lower control arm.
Figure 16

This picture illustrates looking up at the left side lower control arm. Using a 16mm wrench and an E14 external Torx socket, remove the lower mounting fasteners.

Remove the E14 external Torx fastener from the lower control arm.
Figure 17

Remove the E14 external Torx fastener from the lower control arm.

This picture illustrates the rear shock absorber mount (green arrow) viewed from below.
Figure 18

This picture illustrates the rear shock absorber mount (green arrow) viewed from below. The rear shock absorber fits tight in the lower control arm. You can use a mallet and punch to tap out the rear shock absorber from the lower control arm mount.

Remove the shock absorber from the car.
Figure 19

Remove the shock absorber from the car. Installation is the reverse of the removal steps. I suggest you use some strength and compress the new rear shock absorber as much as you can before attempting to install it in between the lower control arm and the body mounting hole. There is usually not enough room to install the rear shock absorber while it is fully extended. Fit the bottom of the rear shock absorber into the mount on the lower control arm and as the rear shock absorber slower extends, guide the upper shock shaft through its mounting hole in the body of the car. You can use your jack to jack up the lower control arm and line up the rear shock absorber lower mounting holes and install the fasteners. Jack up the lower control arm until the shock shaft is fully extended into the mounting hole in the body. Attach the rear shock absorber upper mount bushing and tighten down the fastener. Flip back up the trunk interior side panel and the two plastic rivets that mount it. Install the tie down brackets and tighten down the fasteners. Fit the plastic covers and install any carpeting you may have removed. Fit the wheel and lower the car.

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Comments and Suggestions:
reggie Comments: front left door window regulator and motor. how do I remove the old one and install a new one
July 18, 2014
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