A Guide to Front Suspension Control Arms for the 2005-2009 Mercedes-Benz E320
Address the common clunks, wandering steering, and vibrations caused by worn E320 control arms.
- The most common failure points are the bushings on the forward lower control arms (thrust arms), causing clunking noises and steering vibrations.
- A four-wheel alignment is mandatory after replacing any control arm to prevent dangerous handling and rapid tire destruction.
- It is strongly recommended to replace control arms in pairs (left and right) to ensure balanced suspension performance.
- For this critical part, choosing a quality aftermarket brand like Delphi or CRP is a safer investment than budget brands like URO, which have a reputation for premature failure.
Signs of a Failing Control Arm on Your E320
The bushings and ball joints in the control arms are considered wear-and-tear items. On the W211 chassis E320, the forward lower control arm bushings (also called thrust arms) are a known weak point that can fail in as little as 40,000-50,000 miles. When they fail, you will notice distinct symptoms.
- Clunking or Creaking Noises: This is the most common symptom. You may hear a clunk, knock, or creak from the front end, especially at low speeds when going over bumps or turning.
- Steering Wheel Vibration: A worn bushing or ball joint can cause excessive vibration or a shimmy to be felt through the steering wheel. This can get worse during acceleration or braking.
- Unstable Steering: The car may feel like it's 'wandering' or pulling to one side, requiring constant steering corrections to keep it driving straight. This indicates a loss of alignment precision due to play in the arms.
- Uneven Tire Wear: Because the control arms hold the wheel in alignment, a worn arm will cause the tire to sit improperly on the road, leading to rapid wear on the inner or outer edge.
Choosing the Right Aftermarket Control Arm
When shopping for a replacement, you'll find a wide range of brands and prices. For a critical suspension part on a Mercedes-Benz, quality matters. Forum discussions among W211 owners show a clear preference for higher-quality brands to avoid doing the job twice. It is almost always more efficient to replace the entire control arm assembly rather than trying to press out and install new bushings.
Aftermarket Brand Quality Tiers
| Tier | Brands | Assessment |
|---|---|---|
| Premium Aftermarket | Delphi, CRP, Vaico | These brands are known for providing good quality parts that are considered reliable replacements. Delphi is a major OE supplier for many manufacturers and is generally trusted for European cars. Vaico is a German brand, and its 'Q+' line signifies OEM-level quality. CRP is also a respected name in the European aftermarket space. |
| Economy Aftermarket | Dorman, URO Parts, Suspensia, Beck Arnley | These brands offer a lower price point, but caution is advised. Forum discussions frequently contain reports of premature failure from budget brands like URO Parts, with bushings and ball joints wearing out in as little as a year. While Dorman is a large company, many enthusiasts recommend avoiding budget parts for critical suspension components on a Mercedes. These may be suitable for a short-term fix but may not provide the longevity and performance of higher-quality options. |
Pro Tip: Many mechanics and enthusiasts consider Lemförder to be the original equipment manufacturer (OEM) for Mercedes-Benz suspension parts. While not on the provided list, it serves as a benchmark for the highest quality available.
Known Issues, Recalls, and TSBs
There are no active NHTSA safety recalls for the suspension on the 2005-2009 Mercedes-Benz E320. However, Mercedes-Benz has acknowledged front suspension noises on this platform through Technical Service Bulletins (TSBs). TSBs like #LI46-40-P-047549 and #322232 were issued to address cracking, creaking, and rumbling noises from the front axle, confirming the prevalence of this issue.
Frequently Asked Questions (FAQ)
Do I have to get a wheel alignment after replacing control arms?
Yes, absolutely. A four-wheel alignment is mandatory after replacing any control arm. The control arm directly determines the wheel's alignment angles. Skipping the alignment will result in poor handling, crooked steering wheel, and extremely rapid tire wear.
Should I replace control arms in pairs?
It is highly recommended to replace control arms in pairs (both left and right sides). If one side has failed due to age and mileage, the other side is likely not far behind. Replacing them in pairs ensures balanced handling and predictable steering, and it prevents you from having to do the same job again in the near future.
Can I just replace the bushings instead of the whole arm?
While technically possible for some bushings, it is not recommended. The process requires a large hydraulic press and special tools to remove the old bushing and install the new one without damage. Furthermore, many control arms on the E320 have integrated, non-serviceable ball joints. Given the labor involved and the fact that the ball joint is also a wear item, it is far more time- and cost-effective to replace the entire control arm assembly.
How do I know which control arm to buy? My car has several.
The E320 front suspension has three arms per side: one upper arm, one forward lower arm (thrust arm), and one rearward lower arm (spring control arm). They are not interchangeable. You must correctly identify which arm is worn out before ordering. If you are unsure, have a mechanic inspect the vehicle to pinpoint the source of the noise or play.
Technical Specifications
The front suspension consists of an upper control arm, a forward lower control arm (thrust arm), and a rearward lower control arm (spring link) per side. Parts are specific and not interchangeable. Part numbers must be verified for your specific vehicle's configuration (e.g., RWD vs. 4Matic, standard vs. sport suspension).
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Mercedes-Benz E320: