1999 Ford Taurus & Mercury Sable Front Steering Knuckle: Diagnosing Noises and Compatibility

Symptoms of a Failing Front Knuckle Assembly

The steering knuckle itself is a robust piece of cast iron or aluminum with no moving parts, so it rarely fails unless physically cracked in a collision or from extreme corrosion. However, the components attached to it—the lower ball joint and the wheel bearing—are common wear items. The symptoms you experience are almost always from one of these two parts failing.

Symptoms of a Bad Lower Ball Joint

The lower ball joint is the pivot that connects the knuckle to the lower control arm. When it wears out, it becomes loose, leading to distinct noises and handling problems.

• Clunking or Popping Noises: A worn ball joint will often make a clunking, knocking, or popping sound that is most noticeable when driving over bumps, dips, or making sharp turns at low speeds, like in a parking lot.
• Steering Wander: The vehicle may feel like it's drifting or wandering on the road, requiring constant small steering corrections to keep it straight. This is caused by excessive play in the joint.
• Steering Wheel Vibration: A loose ball joint can cause vibrations that you can feel through the steering wheel.
• Uneven Tire Wear: Inspect your front tires. Accelerated wear on the inside or outside edges is a classic sign that a worn ball joint has thrown off the wheel alignment.

Symptoms of a Bad Wheel Bearing

The wheel bearing is housed within the wheel hub, which bolts directly to the steering knuckle. Its failure produces a very different set of sounds.

• Grinding or Humming Noise: The most common symptom is a steady grinding, humming, or roaring sound that gets louder with vehicle speed. The sound may change in pitch or disappear when you turn one direction and get louder when you turn the other.
• Vibration: A failing bearing can cause vibrations felt in the steering wheel or through the floor of the car.
• Loose Steering Feel: The steering may feel less precise or 'loose' due to play in the worn bearing.
• Wheel Wobble or Play: In advanced stages of failure, you can physically wiggle the top and bottom of the tire when the car is jacked up. This is a critical safety issue.

Known Issues, Recalls, and TSBs

While there are no recalls specifically for the 1999 steering knuckle, there is a major safety recall for the front suspension that all owners of 1999 Taurus and Sable vehicles should be aware of.

Safety Recall 04S17: Front Coil Spring Fracture

Ford issued a recall for 1999-2001 Taurus and Sable models, particularly those registered in states where road salt is used in winter. The protective coating on the front coil springs can chip, allowing the spring to corrode and potentially fracture. A broken spring can then contact the front tire, causing it to rupture suddenly. The remedy was the installation of protective shields on the springs. Even if a vehicle has had this recall performed, the front springs remain a known weak point on these cars.

Buying a Used 1999 Taurus or Sable Knee Assembly

A used OEM steering knuckle is an excellent, cost-effective repair option. The knuckle itself is a durable part, and a recycled OEM unit will have the exact fit and material quality as a new one. However, there are important things to check.

• Confirm Compatibility: The front suspension was redesigned for the 2000 model year. You MUST get a knuckle from a 1996-1999 Ford Taurus or Mercury Sable. A part from a 2000 or newer model will not fit.
• Inspect for Damage: Check the knuckle for any visible cracks, especially around the mounting points for the strut and control arm. Ensure the threads for the brake caliper bolts and axle nut are clean and not stripped.
• Check the Ball Joint Boot: The used knuckle will come with a ball joint. Inspect its rubber boot for rips or tears. If the boot is torn, the joint is likely contaminated with dirt and will fail soon.
• Plan to Replace the Bearing: Many used knuckles come with the wheel hub and bearing still attached. It is impossible to know the condition or mileage of this used bearing. It is highly recommended to press out the old hub and install a new wheel hub and bearing assembly while the knuckle is off the car. This prevents having to do the job twice.
• SHO vs. Non-SHO Models: The high-performance Taurus SHO model may have different suspension components. Recall documents list different service kits and procedures for 1999 SHO vehicles, indicating a potential parts difference. Double-check the part number or VIN compatibility if you have an SHO model.

Replacement Overview and Torque Specs

Replacing the steering knuckle is a significant job that requires disassembling most of the front suspension. It is considered a moderately difficult task for a DIY mechanic. Rust can make removing the old components, especially the axle shaft from the hub, very difficult.

Related Parts to Inspect

While the knuckle is removed, it is the perfect time to inspect and, if necessary, replace related components:

• Wheel Hub & Bearing: Strongly recommended to replace with new.
• CV Axle Shaft: Check the boots for tears and the joints for play.
• Outer Tie Rod End: Check for any looseness or play.
• Sway Bar End Link: These are often difficult to remove without damage and are inexpensive to replace.
• Lower Control Arm Bushings: Look for cracked or deteriorated rubber.

Key Torque Specifications

Using a torque wrench is critical for suspension work. Improper torque can lead to component failure. These are the key specs for the 1999 Taurus and Sable. Always confirm with a vehicle-specific service manual.

Cost of a New vs. Used Steering Knuckle

The cost to replace a steering knuckle can vary significantly. A used OEM part offers substantial savings over a new dealer part, making it a great value.

Frequently Asked Questions