When I was working to add an OEM trailer hitch to my 2012 ML350 BT I discovered that the right rear suspension spring was broken. After getting the hitch taken care of, I ordered (2) new springs. I will try and list the steps I went through to get it changed. As it was the opposite spring was broken as well.




I initially raised the car to remove the wheel and then I used a second jack to raise the lower control and compress the broken spring. Once the spring is compressed almost to the point that the load on the first jack is greatly reduced trying to compress the spring sufficiently for its removal. I then use multiple wraps of cordage to keep the spring in compression for its removal.



With the spring wrapped you can lower the jack under the control arm. During this process you will need to disconnect the lower shock connection and the torsion bar link that is connected to the torsion bar, this is to allow more down travel of the control arm. Please note that on the passenger side you should disconnect the axile position sensor link, so it isn't damaged while lower control arm is moved to an extended travel position. On the second spring I not to wrap it but allow it to go to full extension and then cut it. You need to make sure that is very close to being loose before cutting. This is instead of using an actual spring compression tool.


Broken Spring

Next photo is the fixture that I used to compress the new spring for install into the car, which once compressed to about 9". The boards must be made from a good hardwood like oak or walnut. Remember that this spring will under lots of tension and extreme care needs to be taken!



Spring Compression Fixture

Spring in compressed state.

With the spring compressed and removed from the compression fixture move the spring interface element to the top of the new spring. Clean the area where the bottom spring interface mounts. Note this part is keyed and is used to orient the spring to the correct position.


Spring upper car connector assembly ( note this is photo of old spring )

Before mounting the spring, you will need to push on the axile brake assembly to create enough room to insert the spring. Note if not done already remove the jack that was used to compress the spring initially.


My third hand to extend lower control arm beyond it's normal travel.

The lower arm extended, you can maneuver the compressed spring into position, first get the lower part of the spring engaged with spring car interface piece. Note that the upper spring is leaning to the inner part and needs to be rotated about the bottom to reinsert the top spring interface onto the centering pin mounted on the spring pilo-block on the car, with spring centered on the pin release the jack that is spreading the lower control arm. Once on the pin, now rotate the spring until the end of the spring is stopped by spring locator stop on the interface. Once this is done then the you can relax the jack that was used to extend the lower control arm.

Last Steps: With the spring in correct position remove the lower control arm spreader jack and then install the jack to raise the lower control arm and compress the spring. Spring compressed the rope pieces can be removed. With spring free reconnect the torsion bar link and the rear shock. Last item is to remount the wheel and torque the lug nuts once the auto jack is lowered and removed. As I look back over this job, I wish I had taken a few more photos especial toward the end of the job.