2016-2018 Mazda CX-9 Steering Knuckle & Bearing: Noise, Failure, and Replacement

Symptoms of a Failing Steering Knuckle Assembly

On the 2016-2018 CX-9, failure symptoms almost always relate to the integrated wheel bearing wearing out. Less commonly, the knuckle itself can be bent or cracked from a severe impact.

Noises and Vibrations from the Wheel Bearing

The most common sign of a problem is noise coming from one of the front wheels. You may hear:

• Humming or Roaring: A deep hum or roar that starts around 20-30 mph and gets progressively louder with speed is the classic sign of a bad wheel bearing. The noise may change in pitch or intensity when you turn the steering wheel, loading or unloading the failing bearing.
• Grinding or Growling: As the bearing deteriorates further, the noise can become a more aggressive grinding or growling sound, indicating metal-on-metal contact inside the bearing.
• Vibrations: A worn bearing can cause vibrations felt in the steering wheel or through the floor of the vehicle, especially at higher speeds.
• ABS Warning Light: The wheel speed sensor (part of the Anti-lock Braking System) reads a magnetic ring on the wheel bearing. A failing bearing can disrupt this sensor's reading and trigger the ABS light on your dashboard.
🎬 Watch this video to learn how to diagnose a bad wheel bearing.

Steering and Alignment Problems

If the knuckle itself is bent from hitting a curb or a major pothole, you will likely notice significant steering issues. These include:

• The vehicle pulling hard to one side.
• A crooked steering wheel when driving straight.
• Uneven or rapid tire wear, often on the inside or outside edge of one tire, that cannot be corrected with a standard wheel alignment.

Known Issues, TSBs, and Recalls for 2016-2018 Mazda CX-9

While generally reliable, this generation of the CX-9 had one specific recall involving the steering knuckle.

Recall 9316D: Loose Strut-to-Knuckle Fasteners

Some early production 2016 Mazda CX-9 vehicles were recalled because the nut and bolt connecting the front strut to the steering knuckle may not have been tightened correctly at the factory. Over time, these critical fasteners could loosen and potentially allow the strut to separate from the knuckle, which would cause a sudden loss of steering control. The fix involved dealers inspecting the fasteners and, if loose, replacing and tightening them to the correct specification. When installing a replacement knuckle, it is critical to use a torque wrench on these bolts.

Buying a Used 2016-2023 CX-9 Steering Knuckle: What to Look For

Since the wheel bearing is integrated, buying a used steering knuckle requires careful inspection. A low-mileage, undamaged used OEM knuckle is an excellent value compared to a new part, offering the same factory fit and quality.

Physical Inspection

• Check for Cracks and Bends: Carefully inspect the entire part for any signs of hairline cracks, especially around the mounting points for the strut, ball joint, and brake caliper. Sight down the part to look for any obvious signs of being bent from an impact.
• Spin the Hub: This is the most important check. Hold the knuckle firmly and spin the wheel hub by hand. It should rotate smoothly and silently. If you feel any roughness, grinding, or hear any noise, the bearing is bad and the part should be rejected.
• Check for Play: Try to wiggle the hub flange. There should be zero side-to-side or in-and-out play. Any looseness means the bearing is worn out.
• Inspect the ABS Sensor: The initial buyer warning is correct. Verify the ABS wheel speed sensor is still attached and that its wire has not been cut or damaged. A missing or damaged sensor will require you to transfer your old one or buy a new one.
🎬 Watch a step-by-step Mazda CX-9 knuckle and bearing replacement.
• Examine Mounting Holes: Ensure the threaded holes for the brake caliper bracket are clean and not stripped. Check that the main strut bolt holes are not damaged or elongated.

Compatibility Verification

The front steering knuckles are confirmed to be the same for all 2016, 2017, 2018, 2019, 2020, 2021, 2022, and 2023 Mazda CX-9 models, regardless of trim level (Sport, Touring, Grand Touring, Signature). They are side-specific, so ensure you are buying the correct part for the driver (left) or passenger (right) side.

Cost of Replacing a CX-9 Steering Knuckle Assembly

Replacing the steering knuckle is a moderately expensive repair. Opting for a quality used OEM part can offer substantial savings without compromising on fit or quality. Note that a four-wheel alignment is mandatory after this repair and will add to the total cost.

Replacement Overview & Critical Torque Specs

This job is feasible for an experienced DIY mechanic with the right tools. The key challenge is dealing with potentially rusted bolts and having the tools to apply high torque values safely.

Key Steps

1. Safely lift and support the vehicle on jack stands.
2. Remove the wheel, brake caliper, caliper bracket, and brake rotor. Suspend the caliper securely; do not let it hang by the brake hose.
3. Remove the axle nut. This typically requires a large 32mm socket and a breaker bar.
4. Disconnect the ABS sensor wire.
5. Separate the steering tie rod end and the lower ball joint from the knuckle. A ball joint separator tool may be needed.
6. Remove the two large bolts holding the knuckle to the bottom of the strut assembly.
7. Remove the old knuckle assembly and install the new one in the reverse order.
8. A full four-wheel alignment is required after installation. 🎬 See this video walkthrough for replacing the front wheel bearing and brakes.

Torque Specifications

Using a torque wrench is critical for safety, especially for the strut and axle nuts. These values are for reference; always consult a model-specific repair manual for exact figures.

Frequently Asked Questions (FAQ)