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Pelican Technical Article:

How to Replace Mercedes Benz Front Struts and Springs

Steve Vernon

Time:

2 hours2 hrs

Tab:

$110

Talent:

*

Tools:

Jack, jack stands 17mm socket and wrenches, adjustable wrench, 8mm Hex, Mercedes-Benz Spring Compressor BM-924-0231

Applicable Models:

 
Mercedes-Benz W124 (1986-95)
Mercedes-Benz W126 (1981-91)
Mercedes-Benz W201 (1984-93)

Parts Required:

New struts and springs

Hot Tip:

Loosen your wheels before lifting the car

Performance Gain:

Better handling

Complementary Modification:

New rear shocks

Check out some other projects from our technical library:

One of the most popular Do-It-Yourself projects to perform is the replacement of the front struts and springs. I usually recommend that you replace both the front and the rear at the same time, as they take the same abuse over their lifetime. As a rule, the shocks should always be replaced in axle pairs either front or rear (left and right together). In this article, we will focus on the replacement of the front struts and springs.

I recommend that you replace your shocks every five to seven years - 50,000 miles or so, or when they start to feel weak or worn out. These are gas over hydraulic shocks. The "antique" push down on a corner of the car and watch for bounce/rebound will NOT work. The gas charge IS critical to suspension handling/ride quality, and when it fails the hydraulic component will still pass a bounce/rebound test. Many owners are stunned by the drastic "it's a new car" change in suspension handling/ride quality because the old shocks and struts where driven years beyond failure.

Different driving patterns may also affect the life of struts and shock absorbers. Cars that are raced or driven hard on windy roads may need to have their shocks replaced more often than typical street cars. It is important to remember if you install performance springs into your car that raise or lower it from its stock level, you will need to have the car realigned and install shocks and struts that are designed to work with the shorter springs. Changing the height of the suspension changes the values of the suspension settings.

Changing the struts is relatively easy, requiring the use of various sockets and a floor jack. However, changing the springs requires the use of a special Mercedes-Benz tool, a heavy duty internal spring compressor. I highly recommend that you use the Mercedes-Benz spring compressor tool as the springs are under a tremendous amount of pressure and can cause serious damage to both you and the car if not compressed correctly. I have yet to been able to find a spring compressor tool at a local parts store that can properly and safely compress the springs on a Mercedes-Benz. Warning: never use air impact tools on the Mercedes style spring compressor, it will wreck the tool and can cause it to fail.

The first step is to raise the vehicle and secure it properly on jack stands. Please refer to our Pelican Parts Technical Article on Jacking Up Your Benz for more info. Once secured, remove the front wheel. After the wheel is removed, you'll see all the components that make up the front suspension. On our project car, the front strut was leaking, the bump stop was shot and the protective boot was almost completely missing. You should not let your suspension get to this point before you replace it. The next step is to place a floor jack under the front control arm. Raise the floor jack to support the control arm while making sure you do not lift the car off the jack stands or make it unstable. This prevents the control arm from flying downward once the upper control arm link and shock are disconnected.

At the top of the car, inside the engine bay, you'll see the upper strut mount. The strut sits in a large metal flange and is held in place by a 22mm nut over an 8mm Hex key (Allen) stud. Hold the 8mm Allen stud in place and use a 22mm wrench to remove the nut. With the nut off you can remove the flange from the mount.

Disconnect the three 17mm bolts holding the strut to the steering knuckle. Remove the three lines that are held in place in the plastic piece attached to the strut. Remove the three bolts so the strut can be compressed and pulled out of the wheel well. Make sure you support the steering knuckle from swinging free and damaging it. Once the strut is removed there is nothing holding the knuckle in an upright position and if you do not support it, it will fall and damage components.

Take the strut to your bench and gently pry out the plastic piece that holds the lines to the strut. If you are reusing the dust protector and bump stop, remove them from the old strut and install them on the new, otherwise install new ones.

With the strut removed check the upper strut mount that connects the strut to the chassis. Again, on our project car the mount was completely destroyed. The metal weld in the mount had failed and the strut was free to bounce up and down in the car. Remove the mount by undoing the three 13mm nuts connecting it to the body. The new one can only be installed in one direction as one side of it is narrower to fit in the support closest to the engine.

If you are only changing your strut you can just insert the new strut, fasten down the new hardware and you are done. Remember the new strut should have come with new single use hardware. Do not reuse your old hardware.

If you are removing or replacing your spring, it is easier to do it with the strut out, but if the strut is in place it only needs to be unfastened from the top. If you are only removing the spring make sure the lower control arm is supported with a jack so it does not fly downward after you remove the top of the strut.

Place the spring compressor plate as high up as possible into the spring. Place the lower plate as far down on the spring as possible. There should be a minimum of 7 1/2 coils between the plates. Feed the compressor strut through the access hole on the bottom of the control arm, rotate it to lock into the upper plate. Once secured, use a 19mm socket and turn the tool. It will compress the springs as it turns. With the springs safely compressed, slightly lower the front control arm and remove the front spring along with the rubber mount in a forward direction. Warning: never use air impact tools on the Mercedes style spring compressor, it will wreck the tool and can cause it to fail.

Picture 1: With the car safely supported off the ground, place a floor jack under the control arm. This will stop the arm from violently swinging down when you undo the strut.

Picture 2: An examination of the suspension shows that the dust protector is almost completely missing (yellow arrow), the bump stop is almost shot, and the strut is leaking. The green arrow shows the spring. If there is this much damage on the strut it is probably a good idea to change the spring as well.

Picture 3: After the control arm is supported you can remove the strut from its upper housing in the engine compartment. The strut is mounted to a support bracket that is attached to the chassis by three 13mm nuts (green arrows). The strut sits in a large metal flange that sits on two rubber sections of the mount (red arrows).

Picture 4: To remove the strut hold the center of the strut in place with an 8mm Hex and unscrew the 22mm nut. With the nut removed you can simple remove the metal flange and push the strut down into the wheel well.

Picture 5: This photo illustrates where the control arm pivots from (yellow arrows). These bushings wear out and should be carefully inspected when performing this job. (Please see our article on replacing your front control arm bushing for information on replacing these.)There are three 19mm bolts/ nuts that need to be removed to free the strut from the steering knuckle, one lower rear (red arrow), and one upper (green arrow). Note: this photo is for illustration purposes only as at this point in the job the control arm must be supported by a jack.

Picture 6: Illustrated here are the other 19mm bolt and nut (green arrows) that need to be removed from the front of the steering knuckle. Note: this photo is for illustration purposes only as at this point in the job the control arm must be supported by a jack.

Picture 7: Remove the three lines from the plastic clip (yellow arrows) on the strut.

Picture 8: Compress the strut and swing it forward and out from the wheel well.

Picture 9: Make sure you protect the knuckle, brakes, lines, etc from damage by securing the knuckle to the chassis so it can not swing away.

Picture 10: Take the strut to your bench and gently pry the plastic clip from the old strut. You will be installing this piece (insert upper right) on the new strut.

Picture 11: If your old bump stop and dust protector are still good, transfer them to the new strut, other wise install the new stop (yellow arrow), clip (green arrow) and protector (red arrow).

Picture 12: Remove the old strut mount and inspect it. Ours had completely failed and need to be replaced. Check for cracks in the welds and if any are found I recommend replacing them now while everything is apart.

Picture 13: Insert the new mount into its opening in the chassis. It should only fit in one direction as one side (green arrow) is narrower than the others. Secure it down with three 13mm nuts (yellow arrows). These nuts should be nylex nuts to help stop them from loosing up. The red arrows show the rubber areas the flange will sit on. If you are only changing struts, you can simple install the new strut and torque everything to spec.

Picture 14: If you are changing your springs I highly recommend you use this spring compressor tool for Mercedes-Benz. Use of a different tool can cause damage to both you and the vehicle. Warning: never use air impact tools on the Mercedes style spring compressor, it will wreck the tool and can cause it to fail.

Picture 15: Place the upper disk as high as you can get it in the springs and the lower one as low as it will go (red arrows). You should have a minimum of 7 1/2 coils between them to compress the spring enough to remove it.

Picture 16: Insert the compressor strut through the hole in the lower control arm and feed it through the plates. Rotate the strut so it locks into the tabs on the upper plate. Attach your 19mm socket (yellow arrow) and start tightening. The springs will compress while tightening.

Picture 17: With the spring fully compressed, lower the control arm and remove the spring and rubber in a forward motion. If you are replacing the spring carefully uncompress the strut and use it to compress the new spring. Mark the old spring so you know where to insert the plates on the new one.

With the car safely supported off the ground, place a floor jack under the control arm.
Figure 1

With the car safely supported off the ground, place a floor jack under the control arm. This will stop the arm from violently swinging down when you undo the strut.

An examination of the suspension shows that the dust protector is almost completely missing (yellow arrow), the bump stop is almost shot, and the strut is leaking.
Figure 2

An examination of the suspension shows that the dust protector is almost completely missing (yellow arrow), the bump stop is almost shot, and the strut is leaking. The green arrow shows the spring. If there is this much damage on the strut it is probably a good idea to change the spring as well.

After the control arm is supported you can remove the strut from its upper housing in the engine compartment.
Figure 3

After the control arm is supported you can remove the strut from its upper housing in the engine compartment. The strut is mounted to a support bracket that is attached to the chassis by three 13mm nuts (green arrows). The strut sits in a large metal flange that sits on two rubber sections of the mount (red arrows).

To remove the strut hold the center of the strut in place with an 8mm Hex and unscrew the 22mm nut.
Figure 4

To remove the strut hold the center of the strut in place with an 8mm Hex and unscrew the 22mm nut. With the nut removed you can simple remove the metal flange and push the strut down into the wheel well.

This photo illustrates where the control arm pivots from (yellow arrows).
Figure 5

This photo illustrates where the control arm pivots from (yellow arrows). These bushings wear out and should be carefully inspected when performing this job. (Please see our article on replacing your front control arm bushing for information on replacing these.)There are three 19mm bolts/ nuts that need to be removed to free the strut from the steering knuckle, one lower rear (red arrow), and one upper (green arrow). Note: this photo is for illustration purposes only as at this point in the job the control arm must be supported by a jack.

Illustrated here are the other 19mm bolt and nut (green arrows) that need to be removed from the front of the steering knuckle.
Figure 6

Illustrated here are the other 19mm bolt and nut (green arrows) that need to be removed from the front of the steering knuckle. Note: this photo is for illustration purposes only as at this point in the job the control arm must be supported by a jack.

Remove the three lines from the plastic clip (yellow arrows) on the strut.
Figure 7

Remove the three lines from the plastic clip (yellow arrows) on the strut.

Compress the strut and swing it forward and out from the wheel well.
Figure 8

Compress the strut and swing it forward and out from the wheel well.

Make sure you protect the knuckle, brakes, lines, etc from damage by securing the knuckle to the chassis so it can not swing away.
Figure 9

Make sure you protect the knuckle, brakes, lines, etc from damage by securing the knuckle to the chassis so it can not swing away.

Take the strut to your bench and gently pry the plastic clip from the old strut.
Figure 10

Take the strut to your bench and gently pry the plastic clip from the old strut. You will be installing this piece (insert upper right) on the new strut.

Remove the old strut mount and inspect it.
Figure 12

Remove the old strut mount and inspect it. Ours had completely failed and need to be replaced. Check for cracks in the welds and if any are found I recommend replacing them now while everything is apart.

Insert the new mount into its opening in the chassis.
Figure 13

Insert the new mount into its opening in the chassis. It should only fit in one direction as one side (green arrow) is narrower than the others. Secure it down with three 13mm nuts (yellow arrows). These nuts should be nylex nuts to help stop them from loosing up. The red arrows show the rubber areas the flange will sit on. If you are only changing struts, you can simple install the new strut and torque everything to spec.

If you are changing your springs I highly recommend you use this spring compressor tool for Mercedes-Benz.
Figure 14

If you are changing your springs I highly recommend you use this spring compressor tool for Mercedes-Benz. Use of a different tool can cause damage to both you and the vehicle. Warning: never use air impact tools on the Mercedes style spring compressor, it will wreck the tool and can cause it to fail.

Place the upper disk as high as you can get it in the springs and the lower one as low as it will go (red arrows).
Figure 15

Place the upper disk as high as you can get it in the springs and the lower one as low as it will go (red arrows). You should have a minimum of 7 1/2 coils between them to compress the spring enough to remove it.

Insert the compressor strut through the hole in the lower control arm and feed it through the plates.
Figure 16

Insert the compressor strut through the hole in the lower control arm and feed it through the plates. Rotate the strut so it locks into the tabs on the upper plate. Attach your 19mm socket (yellow arrow) and start tightening. The springs will compress while tightening.

With the spring fully compressed, lower the control arm and remove the spring and rubber in a forward motion.
Figure 17

With the spring fully compressed, lower the control arm and remove the spring and rubber in a forward motion. If you are replacing the spring carefully uncompress the strut and use it to compress the new spring. Mark the old spring so you know where to insert the plates on the new one.

When reinserting the spring make sure the lower portion sits in its proper place in the control arm (red arrow).
Figure 18

When reinserting the spring make sure the lower portion sits in its proper place in the control arm (red arrow).

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Comments and Suggestions:
Swede Comments: Thank you very much for this! Awesome guide
May 23, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 

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Page last updated: Fri 9/19/2014 01:22:58 AM