Replacing Rear Shocks on a Mercedes-Benz Ultimate DIY

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You don’t have to be rich or go into debt to drive a luxury car. Anyone that can afford a used Honda or a Toyota could own a BMW or a Benz if they are willing to a) drive an older model and b) get their hands dirty. Today we’ll address the latter with a step-by-step DIY on how to replace the rear shocks on a Mercedes-Benz. This post is based on a Mercedes-Benz C-Series, AKA “W203”, but the general approach is similar on other Mercedes models as well as other car brands. For illustrative purposes all pictures were taken while replacing the rear shocks on a 2003 Mercedes-Benz C320.  While there are other guides on the internet, I found them lacking some important details – stuff that “I wished I knew” before I started. I decided to document the procedure in the most straightforward fashion to crate a definitive one-stop guide on the subject!

If you don’t wanna go broke driving a used German car you simply have to learn how to work on cars. With a right set of tools your German car maintenance costs will be on par with that of a reliable – but boring – Japanese car.

How do I know? I’ve owned several BMW’s, a MINI Cooper (mostly BMW-made), a Mercedes-Benz and a couple of Japanese cars over the last 2 decades. I have a spreadsheet documenting each car’s maintenance costs. I know for a fact that it’s possible to spend the same or just slightly more on German vs. Japanese car maintenance while enjoying the driving feel that only a German car can offer.

This post is about a project that will become relevant sooner or later to anyone driving a high-mileage vehicle – shock replacement. But first let’s answer some questions…

How do I know that I need to replace the shock absorbers?

Is the ride quality worse than before? Is the car nose diving during braking or squatting during take off noticeably more than before? Does the car seem less stable or more floaty/bouncy over bumps? Is there unusual noise coming from the suspension when going over road irregularities? Does it feel like suspension is bottoming out or as if tires crash into potholes? Is there an unusual wear pattern on tires like “cupping”? Is there oil on one or more shock absorbers?

If the answer is yes to any of these questions then you might have a bad shock absorber especially if the car has more than 60,000 miles on it.

Our Mercedes-Benz C320 is 13 years old and has 140,000 miles. Most suspension components have already been replaced but it still has the original shocks. The car started to manifest most of the symptoms recently so there is no doubt that the shocks needed to be replaced.

Should I replace one or two or three or all 4 shocks?

First of all, you should always replace in pairs as it’s generally not recommended to replace just one shock at a time. At such a high mileage I replaced all 4 shocks – 2 struts in the front and 2 shocks in the back. This post will show how to replace the rear shocks only. Replacing the front struts is more complicated and requires special tools.

What brand should I buy?

There are a few options. SACHS is the original equipment manufacturer and the price will be higher. I went with Bilstein struts and shocks. Bilstein is a well-known quality German brand. The ride may feel a bit sportier than SACHS, but most people won’t even notice the difference. You will notice a dramatic improvement in ride quality – no matter what brand!

What will it cost?

You can get no-name shocks from a local store or eBay, but I’d never put that stuff on my car. Plus, the cost of Bilstein’s is very competitive if you get them online. You should be able to get two rear shocks for under $150.

Just for fun, I called a local Mercedes-Benz dealer for a quote. Check out the Google Hangouts voicemail transcript that I received. It’s a bit hard to read but basically the price of each shock is $241.50 plus a mounting kit at $23.31 per side for a total of $530 for the two rear shocks. Then you are looking at approximately 3.5 hours of labor for them to install the shocks which comes to $463.75 ($132.50 per hour!). Total estimated quote to install two new rear shocks at the dealer was $1,046 plus tax. That’s close to 10 times more than what I ended up paying to do it myself.rear_shocks1

How long will it take to replace the rear shocks myself?

I don’t know but I can tell you that it took me, an experienced DIYer using basic tools and without a lift, two hours from the time I pulled the car into the garage to when I was cleaning my hands. If I had to do it again I could probably do it in an hour. I was mostly figuring out stuff as I went along so hopefully these instructions will save you some time.

Is it dangerous?

YES, THIS CAN KILL YOU! Anytime you are working under a car there is risk! Do NOT attempt if you doubt your ability to properly support a vehicle and work in a safe environment. These instructions are a record of how I did the job. I’m not a qualified auto mechanic – just some guy on the internet that enjoys challenging DIY projects. I like to keep a record of various projects I undertake so I can refer to these instructions later when the time comes to do the same job again. If you choose to follow these instructions you must assume all risks!

If in doubt – take the car to a shop! It will be more expensive than a DIY, but it’s a lot safer and you will be supporting a few local working families to boot!

What tools will I need?

The right tools can mean a difference between an enjoyable time in the garage and an obscenities-filled nightmare. The good news is that if you’ve done any sort of car projects before you should already have most of the tools. If not, all of these fall under the “essential tools” category so it’s money well spent. If you plan on doing your own car maintenance this list of a DIY auto mechanic tools is worth a closer look!

Tools

Step-by-Step Do It Yourself Mercedes-Benz C-Class Rear Shock Replacement

With all 4 wheels on the ground, open the trunk and take the carpeted cover over the spare tire out of the car. Take out the plastic cover located between the spare tire and the back seat. The picture below shows the plastic cover and the 2 fasteners that hold it down. The easiest way to remove the fasteners is to simply pull up on the cover and let the fasteners pop out. Or you can use the trim removal tool or a flat head screwdriver to get the fasteners out.rear_shocks2

A word on plastic fasteners. I managed not to break any during this project but they do break easily. If you plan on doing other car work I’d suggest you get a good trim removal tool set. A screwdriver and pliers will often do the job but it’s frustrating and you’re bound to break some clips. Not a big deal either way since you can always buy spares and keep them on hand.   

Next you will be working on the trim pieces that are covering the left and the right sides of the trunk. Starting on the left side (or right, doesn’t matter), look for the 2 fasteners circled in the picture below. Use the trim tool to pry out each fastener and store them away. Each will have two parts and you want both parts out of the car.rear_shocks3

Now you can bend the trim piece back as you see below. There is no need to remove it completely. The shock top is now visible.  rear_shocks4

Do you have a 17mm ratcheting wrench? I wish I did! I have every other size except for the 17mm so I ended up using a regular box wrench. It was somewhat painful… I won’t blame you if you decide to get inside the trunk for this… I did.

Picture below shows how I took off the nut from the shock. I held the top with an adjustable wrench i.e. the threaded rod which has a square top on which the adjustable wrench goes. Then I used a 17mm box wrench to spin the nut off.

As you’re applying force to break the nut loose for the first time, take a mental note on how tight it is. It should be torqued to 22 ft-lbs, which is not much. When you install new shocks, you will need to torque the new nut to approximate 22 ft-lbs. There is no way to use a torque wrench in this set up so it will have to be done by feel. You definitely do not want to apply too much torque on the top nut as I’ve heard stories of stuff shearing off under too much pressure.rear_shocks5

You can take off the nut, the big metal washer and the black rubber washer, still shown on the threaded rod in this picture.rear_shocks6

Do the same on the other side and you’re ready to put the car up on jack stands.

First crack the lug nuts while the car is still on the ground. Then lift the car with a car jack and secure it on jack stands. You need to have just the 2 rear wheels off the ground. You can follow these instructions if it’s your first time lifting the car.

Remove both rear wheels. I like to put them under the car next to jack stands just as another safety measure. Better wheels than me.rear_shocks7

Get under the car and locate a plastic cover over the rear control arm. There will be two 10mm bolts holding the cover in place. Picture below shows a wrench over the first bolt and the second one is directly across, towards the front of the car.rear_shocks8

With 2 bolts removed, pull on the cover and work it off the control arm. No tools are needed, just your hands. In this picture the cover is half off and you can see the 16mm nut that we’ll be working with next.rear_shocks9

Use a 16mm wrench to loosen the nut. If it won’t budge use a breaker bar or your lug nut wrench to give you leverage. If it doesn’t want to come off you might want to try some penetrating oil. Mine came right off, which is good news after 13 years in a worst possible spot on a car.rear_shocks10

Once the nut is loose you will need to hold the bolt on the other side so it doesn’t spin. In the picture below I’m using a lug nut wrench to hold the bolt but then I later found that a 16mm box wrench worked even better.rear_shocks11

You should soon be able to take off the nut and take out the bolt.rear_shocks12

The shock is now ready to be removed.rear_shocks13

There’re a couple of ways to remove a shock absorber. I found it easiest to grab it with both hands at the bottom and compress it up so that it clears the caliper and then swing it over the brake line towards me. It will then hang there as shown below.rear_shocks14

Now just pull it down and out of the car. I thought this was going to be the hardest part and was pleasantly surprised how easy the shock came out. Just remember to put some muscle into compressing the shock enough to clear caliper hardware. If it’s getting stuck then you’re not compressing it enough. And no, you should not need any tools to compress it – just your two hands and a bit of muscle.

Old vs. new… After 140,000 miles the original shock doesn’t look too bad but it was definitely shot. Take a minute here to compress the old shock by turning it upside down so that the threaded rod is on the floor while you press down with both hands from where the bolt hole is. It should be easy to do and you might hear noises and/or feel rough spots as the shock compresses.rear_shocks15

Now do the same with the new shock and see how that feels. There was a night and day difference in my case which would explain the poor handling and the noises from the rear while driving.

There is another reason to compress the new shock a few times – it will get the oil moving and should make it easier to install.

Now take the rubber dust shield cap that came with your Bilsteins. Just slide it over the threaded rod until it’s flush with the shock top.

To install the new shock, put the threaded rod through the hole into the trunk. Once the shock is hanging like we saw 2 pictures up, compress the shock from the bottom until it clears the caliper hardware and the bottom bolt hole lines up with the holes in the control arm. There is no wrong way to install the shock as long as the top threaded rod goes through into the trunk and the bottom hole lines up with the holes in the control arm.rear_shocks16

The Bilstein shock will come with a new bottom bracket bolt, two small washers and a nut. Take the bolt, put one washer and insert the bolt into the control arm and through the shock. You want to insert the bolt from the front of the vehicle to the rear. Then put the second washer and the nut – both will be facing the rear of the vehicle.

Tighten the nut to 41 ft-lbs with a torque wrench. You will need to counter-hold the bolt with a 16mm wrench so it doesn’t spin.rear_shocks17

Put the plastic shield back on and secure the two 10mm bolts. Repeat on the other side to replace the second shock.

You are now ready to lower the car. Put the wheels back on and SLOWLY start lowering the car stopping every inch or so at first. You want to make sure that the threaded rod of each shock goes into each hole on top without snagging or messing up the threads. Once the threads are inside the trunk you are in the clear and can lower the car the rest of the way. In this picture you can see that threads have cleared and they are inside the trunk.rear_shocks18

You could accomplish the same thing by jacking up each control arm after the shock is installed and putting the top nut on the threaded rod in the trunk. Either way should work and I just want you to be conscious of the potential damage to the threads, which would suck at this point in the process!

With the car back on the ground you can finish up in the trunk. Take the new rubber washer that came with your Bilstein’s and put it over the threaded rod sticking out in the trunk. Now put the new washer and the new self-locking nut and tighten. Recall what I said about the top nut in the beginning and don’t over tighten. Try your best to approximate 22 ft-lbs, unless you have a special tool that will allow you to use a torque wrench (I didn’t).

After both sides are finished it’s time to put the trunk together. Put all the panels back in place and snap all fasteners in. Remember to separate the pin-type fasteners so that you are inserting round one in the hole first and then putting the pin one in last. To easily separate the two, use a flat head screwdriver to push the pin out.

That’s all there is to it! Even if it took close to 3,000 words and a couple of days to describe it…

Despite the length of this post the actual process is very straightforward and this DIY documents everything you need. I hope you learned something new. Please feel free to share any questions or comments below. With your help this can become the ultimate DIY guide on replacing the rear shocks on a Mercedes-Benz W203!