Mercedes Air Suspension Strut Airbag Replacement DIY

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

A ruptured spring bladder or leaks on the rubber O-rings of the air spring often cause Mercedes air suspension failures. It requires replacing the air spring, which can be a DIY project if you are up to the challenge.

Problem

Mercedes’s 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 hear 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 rise when restarted. If you start the car and move to the front, you should hear the air compressor engage for a few minutes until the car is raised and turned off.

If a suspension airbag leaks, 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 continues, the air suspension compressor will eventually fail. At that point, you will permanently get a “Stop car too low” red error message on the instrument cluster. The vehicle will no longer raise.

If you are experiencing a 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 remove the air spring (airbag). If you want to save money, you can replace only the air spring, which is the part that fails. Replacing the air spring requires a few extra steps. This tutorial will show how we replaced a bad air suspension strut and spring.

What you will need

Instructions

Here, you will show 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, allowing you to place a jack underneath. You can start the car and wait a few minutes to see if the car will rise enough for you to jack up the car. If that doesn’t work, there is a jack point 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. We also like to slide the wheel under the car as an extra safety measure. Don’t let any weight on the wheel. It’s 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 must remove the fender liner from the wheel well. You will need to remove the plastic pins to remove the liner. For example, if you are replacing the air spring on the R-Class, 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 starts to spin, it will most likely need a Torx bit to prevent it from spinning.

Remove the bolt from the lower control arm that secures the strut. Counter-hold the bolts, or they will spin freely.

Remove all the wires and lines from their mounting bracket.

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

Getting to the top of the air strut is easy for most models. On models such as the R-Class, you must 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 must 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. Two 13mm bolts and two 10mm bolts need to be removed.

The top plate was removed.
Remove three 13mm bolts from the top air strut bolts. Leave at least one nut slightly threaded to hold the strut in place. You will remove the nut when 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 to create enough room to pull out the old strut. Remember to remove the last nut from the top of the strut when ready for this step.

Reinstall the new air suspension strut in reverse order.

Don’t overtighten the copper nut by the airline, 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 also replacing the air spring, 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 the instructions in Part 1 to remove the air strut.

You must remove the metal clip that holds the cap in place. It requires the cap to be pushed down to remove the clip. You must get creative if you don’t have the proper tool for this step. Remove the 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 the 17mm bolt that secures the strut.

Pull out the air spring below.

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

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

Reinstall the air strut in reverse order.