Mercedes-Benz Parts Catalog Mercedes-Benz Accessories Catalog Mercedes-Benz Technical Articles Mercedes-Benz Tech Forums
 
Follow Pelican Parts on Facebook Follow Pelican Parts on Twitter Follow Pelican Parts on Instagram Follow Pelican Parts on YouTube Follow Pelican Parts on Pinterest Follow Pelican Parts on Tumblr
  Search our site:    
View Recent Cars  |   Cart  | Project List | Order Status | Help    
 >  >
Rear Shock Absorber Removal and Replacement
 
Bookmark and Share

Pelican Technical Article:

Rear Shock Absorber Removal and Replacement

Kerry Jonsson

Time:

2 hours2 hrs

Tab:

$400

Talent:

**

Tools:

16mm, 17mm wrenches, sockets with ratchet, small vise grips

Applicable Models:

Mercedes-Benz R129 (1990-02)

Parts Required:

Rear shock absorber

Hot Tip:

Spray the fasteners with penetrating oil before removing

Performance Gain:

Improve ride and stop excessive bouncing over bumps

Complementary Modification:

Replace the rear sway bar links if necessary

The Mercedes Benz W129 chassis uses a multiple link rear suspension. These links form the main components of the rear suspension system. Between the body of the car and the lower control arm is a coil spring that supports the weight of the vehicle. It also absorbs the initial shock as the suspension reacts to bumps in the road. Of course with any coil spring as it is compressed it becomes under tension and wants to expand back as soon as it can. This reaction slams the wheel into the ground forcing the body of the car to go up. This is why the car bounces up and down as you drive over bumps. The main job of the rear shock absorber is to slow down the return of the coil spring to its normal size. This prevents the wheel from being slammed back into the road. It does help with some compression dampening and supplements the rear coil spring but this is not its main job. Over time the rear shock absorber internal valves wear out. This makes the rear shock absorber ineffective in controlling the rate of the coil spring return to its normal shape, which results in the rear end of the car bouncing excessively over bumps. This makes the car feel uncontrollable and does not keep the tires of the car in contact with the road as well as a good set of shock absorbers would. In this tech article I will go over the steps to replace your rear shock absorbers and restore the ride of the vehicle.

Lift and support rear axle of the vehicle. Before you get under your car put on a good pair of safety glasses. Trust me, getting rust in your eyes is no fun. 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.

The procedure to replace the rear shock absorber is the same for both the left and right side. In these pictures I am 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 had parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts I give may be different from what you have so be prepared with different size sockets and wrenches. Our rear shock absorbers were already replaced. The original lower fasteners were 17mm and our replacement rear shock absorbers changed the fasteners sizes to 16mm.

ThisPicture illustrates under the rear of the car on the left side looking at the inner part of the lower control arm.
Figure 1

ThisPicture illustrates under the rear of the car on the left side looking at the inner part of the lower control arm. Remove the 10mm fastener (green arrow). You do not need to remove the roll-bar sensor to remove this fastener. You can just move the sensor arm down (as shown in photo) to give you more room to remove the fastener.

On the front side of the control arm remove the 10mm fastener (green arrow).
Figure 2

On the front side of the control arm remove the 10mm fastener (green arrow).

Remove the lower control arm plastic cover, pull it straight off the control arm to detach it.
Figure 3

Remove the lower control arm plastic cover, pull it straight off the control arm to detach it. You do not need to remove the brake caliper and rotor to perform this procedure. We have removed the rear brake caliper and rotor to provide you with a better view of what I're doing.

Working at the lower control arm, loosen the lower16mm fastener for the rear shock absorber.
Figure 4

Working at the lower control arm, loosen the lower16mm fastener for the rear shock absorber. Our replacement fasteners were 16mm but original fasteners would be 17mm so be prepared with additional size wrenches and sockets. Do not remove the fastener from the lower control arm yet. Use a jack to support the lower control arm from falling down.

Use a jack to support the lower control arm.
Figure 5

Use a jack to support the lower control arm. You may have to lift it to take the tension off of the fastener (green arrow). Pull the fastener out in the direction of the blue arrow (pulling up and out).

Working in the trunk, fold the carpet on the left side of the trunk out of the way until you can see the access hole for the shock.
Figure 6

Working in the trunk, fold the carpet on the left side of the trunk out of the way until you can see the access hole for the shock. ThisPicture shows the left side of the trunk with the forward carpeted panel folded out of the way. Remove the 17mm fastener (green arrow) for the rear shock absorber upper mount. You may need to use a small pair of vise grip pliers to hold the rear shock absorber shaft (yellow arrow).

You do not need to remove the rear gas tank panel to remove the rear shock absorber upper body mount but it does give you much more room to fit Vise Grips (green arrow) and a wrench.
Figure 7

You do not need to remove the rear gas tank panel to remove the rear shock absorber upper body mount but it does give you much more room to fit Vise Grips (green arrow) and a wrench. Here I have done so to give you a better view of all the action. See our tech article on fuel level sending unit removal to remove the fuel tank panel.

Remove the rear shock absorber upper bushing from the top of the rear shock absorber.
Figure 8

Remove the rear shock absorber upper bushing from the top of the rear shock absorber.

Lower the jack and push the upper shaft of the rear shock absorber (green arrow) down slightly and remove it from the mounting hole in the body (yellow arrow).
Figure 9

Lower the jack and push the upper shaft of the rear shock absorber (green arrow) down slightly and remove it from the mounting hole in the body (yellow arrow).

Pull the rear shock absorber upwards to remove it from its mount in the lower control arm.
Figure 10

Pull the rear shock absorber upwards to remove it from its mount in the lower control arm. This may be a tight fit. You can tap it out of the lower control arm mount with a mallet or lever it out with a small pry bar. Installation is the reverse of the removal steps. Typically, the shock absorber is usually too long to fit neatly in between the lower control arm and the body mounts. I suggest you use your weight and strength to compress the shock absorber as much as you can before installing. While the rear shock absorber is slowly expanding, position it in the lower control arm and allow it to fully expand in the upper body mounting hole. You can then use a jack to help line up the lower control arm fasteners mounting holes and raise the shock absorber fully into the upper body mount to install the bushing and tighten down the upper bushing mount. Fit the lower control arm cover with the two fasteners and the wheel. When you're all done you can be satisfied with your good job every time you take your M-B out for a nice spin around town. I don't think you'll miss the bouncing around.

Bookmark and Share

  Search our site:    

View Cart & CheckOut | Project List | Order Status |  Help    

 

[Home] [Customer Service] [Shopping Cart] [Project/Wish List]
  [Privacy Statement]  [Contact Us] [About Us] [Shipping] [Careers]

Copyright © Pelican Parts Inc. -    DMCA Registered Agent Contact Page

Page last updated: Fri 12/9/2016 02:28:22 AM