2009 S550 PK2 Front Right Hydraulic Suspension Parts: A Complete Guide

If you own a 2009 Mercedes-Benz S550 with the PK2 suspension package, you may be searching for front right hydraulic suspension parts. While the term "hydraulic" is sometimes used interchangeably, the S550 actually uses an air suspension system called Airmatic. The PK2 package specifically refers to a sport-tuned version of that system. This guide covers the essential front right components, common failure signs, and practical advice for replacing them.

Understanding the 2009 S550 PK2 Suspension System

The 2009 S550 W221 chassis features Airmatic air suspension, which uses air springs (air struts) at each corner rather than traditional coil springs. The PK2 package adds adaptive damping with electronically controlled shock absorbers. The front right suspension assembly consists of several key parts:

• Air strut (combines air spring and shock absorber)
• Air line (connects strut to the compressor or valve block)
• Ride height sensor (reports position to the control module)
• Control arm / ball joint (provides wheel location)
• Stabilizer bar link (connects sway bar to strut)

When people refer to "hydraulic suspension parts" for this car, they often mean the Airmatic components—especially the air strut, which contains hydraulic fluid for damping in addition to the air chamber.

Why the Front Right Side Matters

The front right suspension bears significant weight from the engine and transmission. On a 2009 S550 PK2, this corner is prone to leaks from the air strut's rubber bellows or the damping unit. A failed front right strut causes uneven ride height, poor handling, and dashboard warnings.

Common Symptoms of Front Right Suspension Failure

Before buying parts, confirm that your front right side is actually the problem. Look for these signs:

• Vehicle leans or sits lower on the front right when parked overnight
• Air compressor runs frequently or for longer than 30 seconds
• "Airmatic Malfunction" warning appears on the instrument cluster
• Bouncy or harsh ride from the front right corner
• Visible oil or air leaks around the strut or air line connections

If you notice these, the front right strut is a likely culprit. However, also check the ride height sensor and air lines—they can fail too.

Front Right Hydraulic Suspension Parts Breakdown

Air Strut Assembly

The most critical part is the front right air strut. For a 2009 S550 PK2, the OEM part number is typically 221-320-60-13 or a revised version like 221-320-60-13-80. This strut includes:

• Air spring (bellows)
• Shock absorber with internal hydraulic damping
• Upper mounting plate
• Electrical connector for the adaptive damping solenoid (PK2)

Aftermarket options are available from brands like Arnott, Bilstein, and Monroe. Arnott is popular because they rebuild original struts with new bellows and seals at a lower cost than OEM.

Air Line and Fittings

The air line from the valve block to the front right strut can crack or come loose. Use nylon tubing with a 4mm outer diameter. If you replace the strut, inspect the line for kinks or abrasions.

Ride Height Sensor

The front right ride height sensor (part number 221-540-48-17) attaches to the lower control arm. A faulty sensor sends incorrect signals, causing incorrect ride height. You can test it with a multimeter—resistance should change smoothly as you move the arm.

Control Arms and Ball Joints

Worn control arms affect wheel alignment and accelerate strut wear. On the front right, the lower control arm (part 221-330-25-07) and upper wishbone (221-330-36-07) are common replacements. If your car has over 80,000 miles, consider replacing them with the strut.

Stabilizer Bar Link

The front right stabilizer link (part 221-320-00-89) can loosen over time, causing a clunking noise. It's inexpensive and easy to replace.

How to Choose the Right Parts

OEM vs. Aftermarket

• OEM: Exact fit, high quality, but expensive ($600–$900 per strut)
• Remanufactured (e.g., Arnott): Cost-effective ($300–$500), with warranty, and often as reliable as new
• Budget aftermarket: Avoid unknown brands; they often fail within a year

For PK2 vehicles, ensure the strut has the electrical damping connector—non-PK2 struts lack it. If you install a non-PK2 strut, you'll get a warning light and no adaptive damping.

Complete Kit vs. Individual Parts

A front right suspension kit includes the strut, air line, and mounting hardware. Some kits also include the ride height sensor and stabilizer link. Buying a kit can save time and ensure you have all required parts.

Check Compatibility

Double-check the part number against your VIN. The PK2 package on the 2009 S550 can be confusing because Mercedes used several variations. Use your VIN on a dealer parts site or call a specialist to confirm.

Replacement Tips and Considerations

Replacing the front right suspension on a 2009 S550 PK2 is a complex job. The air strut is under high pressure, so you must depressurize the system before removal. Here's a high-level overview:

1. Depressurize the Airmatic system by removing the fuse for the compressor and opening the air release valve on the strut (if equipped).
2. Jack and support the vehicle safely.
3. Remove the wheel.
4. Disconnect the air line at the strut—use a line disconnect tool to avoid damage.
5. Unplug the electrical connector for the damping solenoid.
6. Remove the upper mounting nuts (3 or 4, depending on design).
7. Separate the lower strut fork from the control arm.
8. Pull out the strut—it may require gentle prying.
9. Install the new strut in reverse, using new hardware and lubricating the air line O-ring.
10. Reconnect the air line and electrical connector.
11. Recharge the system by restarting the car and waiting for the compressor to fill the strut.

Crucial: After replacement, you must perform a suspension calibration using a diagnostic tool (like a Mercedes SDS or iCarsoft). This teaches the module the new strut's characteristics. Without calibration, the ride may be uneven.

If you're not comfortable with this, have a specialist do the work. Labor time is about 3–4 hours per side at most shops.

Cost Estimates

• Front right OEM strut: $600–$900
• Remanufactured strut: $300–$500
• Ride height sensor: $50–$100
• Control arm (lower): $100–$200
• Air line and fittings: $20–$40
• Labor (if paying): $200–$400

Total for a DIY job with a remanufactured strut: around $400–$600. If you hire a shop, expect $800–$1,200.

Final Recommendation

For most 2009 S550 PK2 owners needing front right hydraulic suspension parts, the best value is a remanufactured air strut from a reputable supplier like Arnott or Bilstein. Combine it with a new ride height sensor and stabilizer link, as these are common wear items. Avoid the cheapest generic struts—they lack the proper damping calibration for PK2 and will trigger warning lights.

Always confirm part numbers with your VIN, and don't forget to calibrate the system after installation. Specialized shops and Mercedes forums are great resources for further guidance. With the correct parts and careful replacement, your S550 will ride smoothly again.