2006-2008 Jaguar S-Type Front Knee: Decoding Noises, Failures, and R-Model Differences

Understanding the Front 'Knee' Assembly

The front 'Knee' on a 2006-2008 Jaguar S-Type is an industry term for the steering knuckle or vertical link. When you buy a used 'Knee' assembly, it typically includes the main aluminum knuckle and may also come with the wheel hub, bearing, and backing plate attached. The condition and compatibility of this assembly are crucial, as a bent or incorrect part can cause persistent alignment problems, uneven tire wear, and unsafe handling.

Symptoms of a Failing Front Knee or Related Components

Problems in this area rarely stem from the knuckle itself cracking unless it has suffered a major impact from an accident or a severe pothole. More often, the symptoms come from worn-out components attached to or housed within the knuckle, such as the wheel bearing or ball joints.

• Clunking or Knocking Noises: A 'clunk' or 'knock' when driving over bumps is a classic sign of worn suspension parts. This is frequently caused by a bad lower ball joint or worn control arm bushings. You can often diagnose this by jacking up the car and checking for vertical play in the wheel.
• Grinding or Humming Noise: A continuous grinding, humming, or roaring noise that gets louder with speed and may change when turning is a tell-tale sign of a failed wheel bearing. Since the bearing is pressed into the knuckle, this is a common reason for replacing the entire assembly.
• Creaking or Squeaking: A creaking sound, especially when getting in or out of the car or going over speed bumps, often points to a dried-out or failed lower control arm bushing where it attaches to the knuckle.
• Rattling Noise: A sharp, quick rattle over small bumps is often caused by worn sway bar end links, which connect the sway bar to the suspension.
• Poor Steering Response & Pulling: If the knuckle itself is bent from an impact, the vehicle may pull to one side, the steering wheel may be off-center, or it may not return to center properly after a turn. This will also cause persistent alignment issues and rapid, uneven tire wear that cannot be corrected with a standard alignment.

Known Issues, Recalls, and Technical Service Bulletins (TSBs)

While the 2006-2008 Jaguar S-Type has no specific recalls for the front steering knuckle, earlier models did. A recall (S204-R136) was issued for S-Types prior to VIN L92349 due to an under-torqued lower ball joint nut, which could lead to suspension separation. The fix involved checking the torque and, if loose, replacing the entire vertical link assembly. This highlights the importance of the ball joint connection on these vehicles.

Additionally, TSB #20408 was issued for a creaking noise from the front control arm hydro-bush when braking over speed bumps, recommending a control arm replacement. While not a knuckle failure, it is a common source of front-end noise on the S-Type.

There are no other major recalls or TSBs directly related to the front knuckle for the 2006-2008 model years. Always check the specific VIN of a vehicle for any open recalls on the NHTSA website.

Buying a Used Front Knee Assembly

A used OEM knee assembly can be a great value, especially since the knuckle itself is a durable part. However, careful inspection is key.

• Verify the Part Number and Model: Cross-reference part numbers if possible. The left (driver) side is typically C2C39509 and the right (passenger) side is C2C39508. Crucially, confirm if the part came from a standard S-Type or an S-Type R. Look at the brake caliper mounting bosses—they are different.
• Inspect for Impact Damage: Carefully examine the entire aluminum knuckle for any cracks, especially around the mounting points for the control arms and the wheel bearing housing. Check for any signs of bending or warping. A bent knuckle is scrap metal.
• Check Included Components: A used assembly often includes the wheel hub and bearing. Assume the bearing is a wear item and may need replacement. Spin the hub by hand; it should be smooth and silent. Any roughness, grinding, or wobble means the bearing is bad.
• Examine Ball Joint Taper: Inspect the tapered hole where the lower ball joint and tie rod end mount. If the hole is distorted, corroded, or worn, it will not hold the new joint securely, which is a major safety issue.
• Mileage Consideration: The knuckle itself is not a high-wear item, but the included wheel bearing is. For a used assembly, lower mileage is always better. A bearing can fail at any point, but failures become more common after 80,000-100,000 miles. Plan on potentially replacing the bearing if the mileage is high.

Cost of Replacement

Replacing a front steering knuckle is a labor-intensive job that requires a subsequent wheel alignment. Prices can vary significantly based on part choice and shop labor rates.

Related Parts to Consider Replacing

When the front knee is being replaced, it's an ideal time to inspect and replace other nearby wear items, as much of the labor overlaps.

• Lower Control Arms & Bushings: The bushings, especially the large rear hydrobush, are a known wear point causing clunks and creaks.
• Lower Ball Joint: If not already part of a new control arm, this should be inspected for any play.
• Wheel Bearing/Hub Assembly: If the used knuckle doesn't come with a known good bearing, it's wise to press in a new one before installation.
• Sway Bar End Links: These are inexpensive and often cause rattling noises when worn.
• ABS Sensor: Be extremely careful with the ABS sensor during removal and installation. They can be brittle and seize in the knuckle.

Installation Tips & Torque Specs

This is a job for an experienced DIY mechanic or a professional. A press is required to replace the wheel bearing if needed. Always get a professional alignment after the work is complete.

Note: These torque specs are from documentation for earlier models but are likely similar. Always consult the specific workshop manual for your vehicle if possible.

Frequently Asked Questions