MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
Last updated:
In this guide (6 sections)
In this article, you will find step-by-step instructions on replacing the rear strut and coil assembly. The ML 163 chassis uses four wheels of independent suspension. In the rear axle suspension, you will find coil springs that support the back of the car. The W163 uses coil springs and separate shock absorbers on the rear axle. Complete replacement spring/shock assemblies are available and can be installed as a unit, avoiding the need to transfer the spring using a spring compressor.
Is the Rear Strut Assembly Actually the Problem?
Three different rear suspension faults on the W163 produce complaints that sound alike, and only one of them is cured by the assembly on this page.
- The rear sits low or uneven, and the tire may touch the liner under load. That is a collapsed or broken coil spring. Park on level ground and compare the gap above each rear tire; a side to side difference points at the spring.
- The rear keeps bouncing after a bump, the tail squats under acceleration, or there is an oily film down the shock body. That is a worn or leaking shock absorber. A failing shock does not change ride height, so the vehicle can sit perfectly level and still ride badly.
- There is a clunk or knock over bumps, but ride height and damping are normal. That is usually a bushing, a link rod, or a sway bar mount. Fitting a new strut will not quiet it.
The complete unit described here replaces the spring, the shock absorber, and the upper mount together, so it answers the first two cases.
Parts Needed
Rear strut and coil assembly
For ML320 1999 to 2003; ML350 2003 to 2005; ML430 1999 to 2001; ML55 and ML500 2002 to 2005. Rear shock absorbers wear at a similar rate on both sides, so a vehicle with one failed unit is usually close to needing the other. Replacing them as an axle pair keeps damping even from side to side.
Tools Needed
13 mm stubby Ratcheting Wrench
. MUST HAVE
Step by Step Instructions with Pictures
WARNING: The rear coil spring is under significant stored tension and can cause serious injury if it is released improperly. If replacing only the shock absorber and transferring the existing spring, use a properly rated suspension spring compressor and follow the manufacturer’s procedure. Do not attempt to remove a compressed spring using improvised tools. A complete pre-assembled spring/shock unit eliminates the need to compress the spring during this procedure.
- Park on level, stable ground and chock the front wheels. The parking brake acts on the rear wheels, which are the ones about to come off the ground, so it will not hold the vehicle once they are raised. Loosen the rear lug nuts about a quarter turn while the wheel is still on the ground.
- Raise the rear of the vehicle at the lifting points Mercedes-Benz designates for the W163. Jacking on a floor pan, on the rear axle carrier, or on the lower control arm can bend sheet metal or load a component you are about to unbolt.
- Support the vehicle on appropriately rated jack stands at the designated support points, lower the jack onto them, and confirm the car is stable before going underneath. Never work under a vehicle held up only by a jack. Remove the wheel from the vehicle.
- Remove the lining from the wheel housing.
- Remove the plastic cover on top of the strut. Underneath it are three 13 mm nuts that you need to remove.
- Remove the three nuts on top of the spring strut mounting. These three nuts secure the upper shock/spring assembly to the vehicle body. There is very little room to reach the 13 mm nuts. A 13 mm or 1/2-inch ratcheting wrench is the tool that makes this step practical. Limited clearance can make removal difficult even with a stubby ratcheting wrench; click here to see one.
- Remove the nut underneath that connects the strut to the lower wishbone.
- Support the rear lower control arm with a suitable floor jack before disconnecting the sway-bar/link rod and control-arm mounting bolts. Remove the bolt for the link rod. The rear link rods connect the rear control arm and the torsion bar.
- Remove the two bolts at the rear lower control arm and the frame.
- Lower the rear control arm by detaching it from the rear axle carrier.
- Pull out the rear strut once you have enough room to do so. Sometimes, you may need to hammer it out of the lower control arm.
- Install the new strut and coil spring assembly. Do not fully torque the lower control-arm mounting bolts while the suspension is hanging at full droop. Final tightening should be performed at the specified suspension/ride-height position to prevent preloading and premature failure of the control-arm bushings.
Tightening Torques
Replace self-locking/prevailing-torque nuts where specified by Mercedes-Benz. Do not automatically reuse suspension locking nuts simply because they appear undamaged.
- Bottom nut. Where the shock absorber mounts to the lower control arm: 85 Nm
- 13 mm nuts where the strut connects to the frame: 20 Nm.
- Nut for the link rod: 30 Nm.
- Lower control arm to frame/subframe bolts: 135 Nm
Related Guides on MercedesMedic
- Front shock absorber replacement on the W163 ML. The same job at the other end of the car.
- Sway bar and torsion bar bushing replacement on the W163 ML. Where to look when the suspension clunks but ride height is normal.
- Rear brake pads and rotors on the W163 ML. Worth doing while the rear wheels are already off.
Manufacturer Part Number
, 1633202413 163 320 05 13, 163 320 18 13, 163 320 24 13, 163 320 23 13, 163 320 21 13
Before you buy parts, scan every control module, not just the engine. It shows the root fault behind the warning lights and tells you whether the problem is still active. See how to do a full health check.
