Mercedes Air Suspension Strut Airbag Replacement DIY

One of the most common problems on Mercedes-Benz cars is airmatic suspension fails due to a leaking air spring. One morning you start your Mercedes-Benz and are greeted with “Stop Car too low” warning. Don’t panic if your Mercedes lowered to the ground on one corner. In this guide, we will show you how to replace Mercedes-Benz air strut and air spring/airbag.

Mercedes air suspension failures are often caused by a ruptured spring bladder or leaks on the rubber O-rings of the air spring. It requires that the air spring is replaced which can be a DIY project if you are up to the challenge.

Problem

Mercedes front or rear goes down when the car is parked. In most cases, the car goes back up when the car is started but not always. If you pay close attention you may head air leaking from the air suspension when you park the car. The car slowly lowers overnight. If you have a small leak the car will raise up when you restart it. If you start the car and move to the front of the car, you should hear the air compressor engage for a couple of minutes until the car is raised up and then it turns off.

If one of the suspension airbags is leaking, you will get a message stating “please wait briefly” or “Stop car too low” until the car raises. Once the car is raised the error message goes away. If the error keeps coming up the air suspension compressor will eventually fail as well. At that point, you will permanently get “Stop car too low” red error message on the instrument cluster. The vehicle will no longer raise.

If you are experiencing the problem where your Mercedes sags on one corner, repair the leaking airbag as soon as you notice these symptoms. Otherwise, you will shorten the life of the air compressor as well.

Getting Started

The easiest thing to do is replace the whole strut assembly. That way you don’t need to bother with removing the air spring (airbag). If you wanted to save money, you can replace only the air spring which is the part that fails. To replace the air spring requires a few extra steps. In this tutorial, we will show you how we replaced a bad air suspension strut and spring.

What you will need

Instructions

Here you will show you how to replace the front air spring on a Mercedes-Benz. We use an R-Class W251 for demonstration, but other models including SL, E, CLS, ML, GL and S Class use a similar system.

Part 1: How to replace Mercedes airmatic air strut

Park your Mercedes-Benz on a level surface. Engage the parking brakes.

Loosen the lug nuts but do not remove them yet. Just make sure you can break them loose.

Raise the vehicle at the corner that has the failed air spring. Note that the vehicle may be lowered extremely low now allowing you to place a jack underneath. You can start the car, wait a couple of minutes to see if the car will raise up enough for you jack up the car. If that doesn’t work, there is a jack point right under the engine. Look for the rectangular rectangle on the lower subframe.

Always use jack stands in addition to the jack. Secure the other wheels. Set parking brakes. As an extra safety measure, we like to slide the wheel under the car as well. Don’t let any weight on the wheel. Its only there to protect you in case everything else fails.

If you are replacing the air spring on an E-Class or CLS-Class you will need to remove the fender liner from the wheel well. You will need to remove the plastic pins to remove the liner. If you are replacing the air spring on R-Class for example, you don’t need to remove the wheel liner.

Disconnect the electrical connector. It is held in place with a small clip. To remove the cable from the car, you need to slide the connector to remove it.

Here is a video that shows you how to disconnect this wire.

Disconnect the tie upper control arm from the steering knuckle. Use a front end repair kit to remove the upper control arm without damaging the ball joint.

Next we need to disconnect the stabilizer bar link. If the bolt itself starts to spin, which most likely will use a Torx bit to prevent the bolt from spinning.

Remove the bolt from the lower control arm that secures the strut in place. Counter hold the bolts or it will spin freely.

Remove all the wires and lines from their mounting bracket.

Now we need to disconnect the top of the air strut.

On most models, it is easy to get to the top of the air strut. While on models such as the R-Class, it requires that you remove the metal cover over the engine, which is held in place with one long bolt.

In this case we are dealing with an R-Class, therefore we need to remove the metal cover to get to the top of the air strut.

Remove the long bolt that secures the metal cover in place. It requires a Female Torx Socket.

Here is a close up of the bolt.

Remove the plate on top of the air strut. There are two 13mm bolts and two 10mm bolts that need to be removed.

Top plate removed.
Remove three 13mm bolts from the top air strut bolts. Leave at least one nut slighlty threaded to hold the strut in place. You will remove the nut when you are ready to take the strut out.

Remove the air line from the top air spring mount.

Remove the air spring. Push down on the lower control arm in order to create enough room to pull out the old strut. Rember to remove the last nut from the top of the sturt when you are ready for this step.

Reinstall the new air suspension strut in reverse order.

Don’t overtighten the copper nut by the air line or you will damage the rubber o-ring. Tighten the nut by hand then turn it half a turn, that’s it.

If your airline develops a leak here, replace the rubber o-ring.

If you are replacing the air spring as well, go to the next section.

Part 2: How to replace Mercedes Air Spring

This guide applies only if you are replacing the air spring / bellow / airbag. If you purchased a strut and airbag assembly, you can skip this section.

Follow instructions in Part 1 to remove the air strut.

You will need to remove the metal clip that hold the cap in place. It requires the cap to be pushed down, in order to remove the clip. If you don’t have the proper tool for this step, you will need to get creative. Remove metal clip that holds the top cap in place.

Here is the metal clip that needs to be removed. You can’t get it out without pushing the cap down first.

Once the metal clip is removed, you can remove the cap by pulling it out.

Remove 17mm bolt that secures the strut.

Pull out the air spring bellow.

Install the new air spring. Make sure to replace the rubber O-rings. Be careful to not damage them.

Reinstall the 17mm nut. Replace the rubber O-ring for the top cap. Reinsert the top cap. Reinstall the metal clip. You will need to push the top cap down enough in order to get the metal clip in the groove.

Reinstall the air strut in reverse order.