Fiat Wheel Bearing Failure Analysis

Fiat Wheel Bearing Failure Analysis

This 2014 Fiat Abarth was brought in with the customer being concerned about a noise coming from the left rear. He was convinced that it was a tire. The noise was cyclical and it increased with speed. During inspection, the bearing had no detectable play, the tires were evenly worn, and no ABS wheel speed sensor codes were present. On the lift, the left bearing was significantly noisier than the right bearing when turned by hand. But, no extra play could be detected.


It can be difficult to diagnose why a bearing has failed. By the time the vehicle is brought to your shop, the initial damage has been concealed by a complete failure of the bearing.

This 2014 Fiat Abarth was brought in with the customer being concerned about a noise coming from the left rear. He was convinced that it was a tire. The noise was cyclical and it increased with speed. During inspection, the bearing had no detectable play, the tires were evenly worn, and no ABS wheel speed sensor codes were present. On the lift, the left bearing was significantly noisier than the right bearing when turned by hand. But, no extra play could be detected.

PHOTO 1
Wheel bearings never wear out; they fail. If a bearing is properly sized and the lubricant does not break down, the bearing should last a very long time. But, if the bearing is subjected to high loads and impacts, the rolling elements and lubricants can damage the races and create noise and play.

The seal may be the cause of the rear wheel bearing failure. The grease can be seen on the outside of the bearing’s seal and on the area around the axle and brake dust shield. This area should be dry and free from grease. But, what damaged the seal?

It is difficult to say why the seal failed to keep the grease inside the bearing. The damage could have occurred as a result of external factors, like heat from the brakes, corrosion on the stub axle or installation errors. But, internal factors like high loads and bearing surfaces can increase the heat and cause the grease to expand and force it out of the seal.

PHOTO 2
This original wheel bearing has been on the vehicle for only four years and 35,000 miles. This extreme corrosion is not uncommon for vehicles operating in the Rust Belt. While corrosion on the back of the flange is not a functional problem, corrosion on the front of the flange that makes contact with the brake rotor can cause runout.

PHOTO 3
This Fiat has active wheel speed sensors. There is no metallic debris on the sensor’s head. Instead, the particles stick to the encoder ring, which is a series of magnets.

This photo shows the encoder ring for the wheel speed sensor. On this Fiat, it is mounted on the outside of the seal and not on the face. The ring has collected metallic particles from the brakes and road debris. The customer did not report any ABS or stability control malfunction indicator lights. But, if enough metallic debris sticks to the encoder ring, it can cause codes and possible false activation.

PHOTO 4
With the bearing on the bench, the inner race can be removed. This type of damage is called “spalling.” The area of the race has been exposed to higher-than-normal loads and high heat. This causes the heat-treated surface to fatigue in a pattern called spalling. What has occurred is a small defect in the race. This small defect causes heat as the rolling elements travel over the flaw. This can damage not only the metal, but also the grease.

Is there a way to prevent this from happening again? It is impossible to redesign the axle to accept a larger bearing to take higher loads, and it is also impossible for drivers to avoid hitting all of the potholes and curbs. The only way to make sure the new wheel bearing will survive is to use high-quality parts and follow the correct installation procedures.

You May Also Like

CVT Transmissions

The point here is not to fear a customer complaint about a CVT transmission. 

Continuously Variable Transmissions, or CVTs, are more common than you think. Audi, Subaru, Nissan, Ford, GM and many other automakers use CVT transmissions in cars and SUVs. There is no way to avoid them. Chances are there is one in your shop right now. 

What does CVT mean for technicians? On the maintenance side, a CVT transmission requires more or the same frequency of fluid and filter changes as a conventional automatic transmission, and many of the basic procedures are the same. On the diagnostic side, a CVT transmission is less complicated internally than a 6- or 9-speed transmission. Diagnostics with a scan tool are about the same. On the service side, while you may never pull a variator or belt out of a CVT transmission, you can service components like sensors, pumps and valve bodies. The point here is not to fear a customer complaint about a CVT transmission. 

Volvo Modular Engine Service

The Volvo Modular Series engine outlasted Ford and was retired by Geely. The Volvo modular design that can have four, five or six cylinders made its debut in 1990 in the 960 sedan as a six-cylinder and never stopped improving. Related Articles – BMW Cooling System Problems – Audi Active Suspension Service – How To

BMW Cooling System Problems

Let’s take a closer look at this unique water pump, how to replace it efficiently and what other components should be replaced along with it.

Audi Active Suspension Service

The key to servicing these systems is proper information and understanding precisely how these systems operate.

How To Service BMW Tire Monitor Systems

BMW has offered Tire Pressure Monitoring Systems (TPMS) for more than 20 years. These early indirect and direct systems were implemented not to meet the 2007 government mandate but to inform the driver when an expensive Michelin or Bridgestone run-flat tire was deflating. Some 2002 and 2003 models have an indirect system called Flat Tire

Other Posts

Chassis Parts and Alignment Angles

Knowing why the adjustment is required is critical to performing the total alignment.

Wheel Bearings Components

Follow along to learn what you may encounter when dealing with a Gen 1 wheel bearing. This video is sponsored by The Group Training Academy.

Threadlocking Compounds For Vehicle Corners

To get the most out of these “liquid” tools, you first need to know how they work.

Servicing Mercedes-Benz AMG Brakes

Take a look at some of the things you need to know in order to service the brakes on a Mercedes-Benz AMG vehicle.