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Front Struts and Springs Replacement
 
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Pelican Technical Article:

Front Struts and Springs Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$110

Talent:

*

Tools:

Jack, jack stands 17mm socket and wrenches, adjustable wrench, 7mm Allen, Mercedes-Benz Spring Compressor BM-924-0231

Applicable Models:

Mercedes-Benz W124 (1986-95)

Parts Required:

New struts and springs

Hot Tip:

Loosen your wheels before lifting the car

Performance Gain:

Better handling

Complementary Modification:

New rear shocks

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 were driven years beyond failure.

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 be 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.

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. You can see the strut (yellow arrow) and the spring (red arrow).

After the control arm is supported you can remove the strut from its upper housing in the engine compartment.
Figure 2

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 (yellow 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 a 7mm Allen (red arrow) and unscrew the 22mm nut.
Figure 3

To remove the strut hold the center of the strut in place with a 7mm Allen (red arrow) and unscrew the 22mm nut. A standard 22mm wrench is a difficult fit; if you have a O-2 sensor socket it is a perfect fit for removing the nut (yellow arrow).With the nut removed you can simply remove the metal flange and push the strut down into the wheel well.

Remove the'mm bolt (red arrow) that needs to be removed from the steering knuckle.
Figure 4

Remove the'mm bolt (red arrow) that needs to be removed from 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'mm bolt (red arrow) and the'mm nut and bolt (yellow arrow) from the strut to steering knuckle.
Figure 5

Remove the'mm bolt (red arrow) and the'mm nut and bolt (yellow arrow) from the strut to steering knuckle.

Remove the three lines from the plastic clip (yellow arrows) on the strut.
Figure 6

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 7

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 8

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 (red arrow); you will be installing this piece on the new strut.
Figure 9

Take the strut to your bench and gently pry the plastic clip from the old strut (red arrow); you will be installing this piece on the new strut. If your old bump stop and dust protector are still good, transfer them to the new strut. Otherwise, install the new stop, clip and protector.

Remove the old strut mount and inspect it.
Figure 10

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

Insert the new mount into its opening in the chassis.
Figure 11

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 simply 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 12

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 13

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 ' 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 14

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'mm socket (red 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 15

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 un-compress 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 16

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


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Comments and Suggestions:
TheTallJS Comments: For the front shocks, the 2 bolts on either side of the shock base are 19mm, and the through bolt needs a 12mm hex bit and 22mm socket for the nut. I just did it today.
November 12, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
Ofpiste Comments: Can the genuine Mercedes spring compressor tool be rented?
September 29, 2016
  Followup from the Pelican Staff: Possibly. Give The Pelican Parts parts specialists a call at 1-888-280-7799.
- Nick at Pelican Parts
 

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