2007 Mercedes S550 Air Suspension Pump Replacement Part Number

The air suspension system in a 2007 Mercedes S550 provides a smooth, controlled ride, but when the pump fails, the car may sag, ride harshly, or display warning lights. Replacing the air suspension pump is a common repair, but using the wrong part number can lead to improper fitment or performance issues. This article outlines the correct OEM and aftermarket part numbers for the 2007 S550, along with practical guidance for a successful replacement.

Understanding the Air Suspension System in the 2007 S550

The 2007 Mercedes S550 (W221 chassis) uses an Airmatic air suspension system. The pump, also called the air compressor, maintains system pressure and levels the vehicle. It is located in the engine bay, typically on the passenger side near the firewall. Over time, the pump can fail due to worn piston rings, electrical faults, or moisture contamination. Symptoms include a sagging rear end, a hard ride, or a "Visit Workshop" message. Before buying a replacement, it is crucial to identify the exact pump your car needs, as the part number changed during production.

Identifying the Correct Air Suspension Pump Part Number

OEM Part Numbers for the 2007 S550

Mercedes uses original equipment manufacturer (OEM) parts made by suppliers like WABCO or Hella. For the 2007 S550, the primary OEM pump part number is 211-320-0304. This number supersedes earlier versions. However, depending on the production date (early vs. late 2007), you may also see 211-320-0604 or 211-320-0804. The best way to confirm is to check the part number on your existing pump. It is stamped on a metal label or directly on the compressor housing. You can also enter your VIN into a Mercedes parts database to get the correct number. If you have a later build 2007 model (after June 2007), the pump may be part of a newer revision. Always verify with the VIN to avoid buying an incompatible unit. Some 2007 S550s also feature adaptive damping, but the pump itself is the same for both standard and adaptive systems.

Aftermarket Alternatives

Several aftermarket manufacturers produce direct-fit replacement pumps for the 2007 S550. Brands like Arnott, Air Lift, and Dorman offer pumps that often cost less than OEM. The most common aftermarket part numbers for the 2007 S550 are:

• Arnott P-3012: A popular rebuilt unit with a warranty.
• Dorman 949-150: A new pump that includes the relay and fuse.
• Hella 7P0616007: A high-quality aftermarket pump (Hella also supplies OEM).

When choosing an aftermarket pump, check if it includes the necessary mounting bracket, air line fittings, and electrical connector. Some aftermarket pumps do not include the dryer (desiccant cartridge), which may need to be reused from the old pump. Also, be aware that some aftermarket pumps are remanufactured, not new. Ensure the seller provides a warranty of at least one year. Compare prices but prioritize reliability, as a cheap pump may fail prematurely.

Tips for Replacing the Air Suspension Pump

Tools and Preparations

Replacing the air suspension pump on a 2007 S550 is a moderate DIY job if you have mechanical experience. You will need:

• Flathead and Phillips screwdrivers
• 10mm and 13mm sockets
• Torx bits (T20, T25)
• New O-rings or sealing washers
• Jack stands and a floor jack
• Safety glasses

Before starting, depressurize the air suspension system. Locate the Schrader valve on the pump or near the reservoir (some models have a manual vent). Release all pressure by opening the valve or using a scan tool to do it electronically. Failure to depressurize can cause injury or damage. Also, disconnect the negative battery terminal to avoid electrical shorts.

Common Mistakes to Avoid

• Buying the wrong part number: As mentioned, confirm the pump part number on the old unit or via VIN. The 2007 model year had multiple revisions.
• Not replacing the dryer: The desiccant cartridge (dryer) inside the pump can become saturated with moisture. If you reuse a worn dryer, the new pump may fail quickly. Many aftermarket pumps include a new dryer; if not, replace it separately.
• Forgetting to clean the air lines: Dirt or debris in the lines can damage the new pump. Use compressed air to blow out the lines before installation.
• Over-tightening fittings: Air line fittings are delicate. Tighten only until snug to avoid cracking the plastic connectors.
• Skipping the bleed process: After installation, you must bleed air from the system to remove trapped moisture and ensure proper operation. Follow the service manual procedure.

Final Recommendation: OEM vs Aftermarket

For the 2007 Mercedes S550 air suspension pump, the choice depends on your budget and how long you plan to keep the car. If you want a guaranteed direct fit and maximum longevity, the OEM pump (part number 211-320-0304) is the safest option. It comes with a new dryer, all brackets, and connectors. Expect to pay between $400 and $700 for an OEM unit from a dealer or online Mercedes parts retailer.

If you are on a tighter budget, aftermarket pumps like the Arnott P-3012 or Dorman 949-150 are reliable choices. They typically cost $200 to $400 and come with warranties. However, check that the aftermarket pump includes all necessary components. Avoid the cheapest, no-name pumps as they often lack quality control and may fail within months. Also, note that some aftermarket pumps are remanufactured—they may have been rebuilt with new seals and pistons but still carry risk. For a balance of cost and reliability, the Arnott pump is a well-known option among Mercedes enthusiasts.

Regardless of your choice, always replace the pump with a unit that matches your VIN's specification. If you are unsure, consult a Mercedes specialist. Proper installation and bleeding are critical for the system to function correctly. After replacement, perform a system check by raising and lowering the suspension several times to ensure no leaks and normal operation. A correctly replaced air suspension pump will restore ride comfort and safety to your 2007 S550 for many more miles.