This post is about a DIY replacement of the front shocks on a 2008 ML320 CDI with approximately 170,000 miles. It was making squeaking noises when going over speed bumps, minimally improved after replacing sway bar links and bushings.

I searched on this forum and elsewhere and couldn't find a complete description for the DIY. In particular, the spring suspension (as opposed to Airmatic) is more difficult to do - the tight spring makes it difficult to get enough room to clear the lower wishbone end of the shock over the axle for removal and subsequent repair. Prior forum postings like this one ( https://mbworld.org/forums/m-class-w...ent-issue.html) have seemed to end without clear resolution/explanation.

The best source I found is this YouTube video:


The video does a really great job of pointing out what needs to be done. Although he does a spectacular job in clearly pointing out what he is going to do, he then kinds of fast forwards through the actual process. Blink and you might miss it! I used a 6 foot long section of 1 inch black pipe from Home Depot and that made it really quite easy. No sense repeating what he said - follow his instructions and you should get the old shock out easily. Here is a picture of where I put the pipe for good leverage:



However, after getting the shock/strut assembly out I still had a lot of work to do that was not discussed in much detail. So that is what I'll talk about next.

Warning: the spring is really dangerous. When compressed there is a tremendous amount of energy stored up. If you are using lightweight tools they very well might break and kill you. Even though I did this, you should not.

Here is an overview of how the shock/strut assembly fits together:





Here is a pic of the tools I used:



In particular is the Schwaben strut spring compressor set (one link for purchase is here: https://www.pelicanparts.com/catalog...TGEN1_pg57.htm ). To repeat, the springs on this truck are big and beefy. I was happy to pay a premium price for a better tool than you might find on a regular Amazon/Autozone, etc. I usually follow the motto that "tools are free" - the savings obtained from using them makes them "free." And in this case I fear that cheap tools could kill you. Even with this higher end tool it was still a moderate challenge.

In my experience, I found it necessary to have the tool completely open when placing it in the spring. As much compression as possible is necessary, or when fitting the new shock back up through the bellows/stop damper the threaded rod of the shock won't come through to allow the nut to be threaded on. I had to uncompress the spring, adjust the position of the strut compressor, and then re-compress a couple of times to find the right place to fit the compressor on the spring such that I had adequate compression. The following picture is from my first attempt, and it turned out to be inadequate - not enough compression. To repeat myself, I then had to uncompress, adjust fit, recompress. And I was sure to use hand tools only - the tool specifically states not to use an impact gun. My forearms are sore today!



Once fully compressed the 17mm top nut of the shock (part #2 in the diagram above) came out for me with an impact. Note that the rod has an internal fitting for a torx bit inside - this will be important during assembly. Here is a picture:



I replaced the entire bellow/stop damper assembly as well as the shock. I recommend it - the rubber spring seat was old and tired, and the stop damper itself was broken:




When re-assembling the strut assembly, the top nut that screws onto the top rod of the shock will just spin the rod unless you hold the shaft with a torx bit (either T40 or 45, can't remember). So you either need a socket set that allows internal access to the nut, or a very long torx bit that will go through the center of a deep 17mm socket without a socket wrench - the latter is what I did. Here is a picture:




You can use a pipe wrench to turn the socket while the torx bit stops the rod from spinning.

That mostly covers it. Oh, don't just throw the old shocks away. They are still under pressure and dangerous - before recycling the old shocks be sure to drill out your old shocks to release the gas pressure, then run the plunger up and down a dozen times and collect the oil that will come squirting out. Here is the guide that came with my replacement shocks:




I also replaced the nuts on the upper sway bar link, and the axle.

Main torque values that I remember were:
Self-locking nut of bottom shock absorber to wishbone: 265 Nm
Upper ball joint of upper control arm to steering nuckle: 20 NM plus 90 degrees.
Upper sway bar: 100 NM, loosen 180 degrees, then 120 NM plus 45 degrees.
Axle collar nut: 260 NM plus 45 degrees.
Tie rod to steering knuckle: 45 Nm plus 90 degrees.

Hope the information is useful.

 

Hi, very useful, thanks!

I have w166, and every road imperfection became very hard to absorb at 110,000 miles. I decided to change front/rear shocks. What else do you suggest to renew? Thanks

 

My front shocks are leaking. Might have it replaced one day if I still own my w164. Very helpful post. I already have regular sized spring compression tool. But I guess it is too risky to use on the w164 springs.

 

Shock replacement is on my to do list. I've done the fronts multiple times on my airmatic X164 due to failed air bags and it requires some effort to get the shock clear of the control arm and axle even with a deflated air bag. The added difficulty that the non-deflated spring would cause didn't occur to me.

Which shocks did you go with? I'm debating between B4 and B6 Bilsteins.