Failure analysis: 5 methods to find the root cause

Failure analysis of fleet vehicles is a practice that identifies and understands the causes of defects to find the best preventive and corrective measures, reducing maintenance costs and increasing vehicle reliability.

By focusing on this stage of fleet maintenance management, managers can anticipate issues, plan preventive maintenance and avoid unexpected downtime that can compromise operations.

See below:

The importance of identifying and analyzing failures in fleet vehicles
Main types of failure in fleet vehicles
How to perform a fleet failure analysis
Methods for analyzing the causes and effects of vehicle failures
Fundamentals of maintaining a freight vehicle fleet

The importance of identifying and analyzing failures in fleet vehicles

Failure analysis enables preventive maintenance, which is generally less costly than emergency repairs. This happens because keeping control of vehicle condition helps prevent small issues from turning into major defects.

Another factor showing the importance of analyzing vehicle failures is identifying failures at their core, which allows effective corrections and prevents the issue from returning or even new failures arising from a larger underlying cause.

This also leads to greater vehicle durability, with the positive consequence of lower operating costs over the long term.

Main types of failure in fleet vehicles

Fleet vehicle failures can vary and affect different vehicle components. Generally, the most common are:

Mechanical failures

Mechanical failures are among the most common and can involve issues with the engine, transmission, braking system, suspension and steering.

Components such as belts, hoses, bearings and gaskets can wear out or break, resulting in failures that can cause unexpected downtime or even accidents.

Electrical failures

Issues with the battery, alternator, ignition system, wiring and electronic sensors can lead to electrical failures.

These failures can result in starting difficulties, lighting failures, issues with comfort and safety systems, and interruptions in communication between the vehicle's electronic systems.

Tire issues

Tire failures can include irregular wear, punctures, cuts, bulges and pressure loss. When inadequately maintained, the assets can also lose traction, increase fuel consumption and, in extreme cases, cause serious accidents.

Cooling system failures

Failures in this system can include coolant leaks, water pump failures, a faulty thermostat and radiator issues. These issues can lead to engine overheating, causing serious damage that is expensive to repair.

Braking system failures

Braking system failures can include worn brake pads and discs, brake fluid leaks, faulty brake cylinders and ABS system issues.

These failures can lead to increased braking distance and, in extreme cases, inability to stop the vehicle.

Steering and suspension system issues

Steering and suspension are essential to vehicle maneuverability and comfort. Issues in this system can include wear on components such as shock absorbers, springs, bushings and ball joints.

This can result in unstable steering, excessive vibration and irregular tire wear.

How do you perform a fleet failure analysis?

Data collection

The first step in performing an effective failure analysis is to collect detailed data on every failure occurring in fleet vehicles.

This data should include information such as the vehicle's model and manufacturing year, mileage, maintenance history and specific failure details, such as the date, time, location and conditions in which it occurred.

It is essential to use fleet management systems, or systems specific to maintenance management, to record this information in an organized, accessible way.

Pattern identification

After collecting the data, the next step is to analyze this information to identify recurring failure patterns. This can involve looking for failures occurring in specific vehicles, during certain periods or under similar conditions.

Identifying patterns allows the investigation to focus on the most problematic areas and helps determine whether there are common underlying causes.

Root cause analysis

Once patterns have been identified, it is time to perform an in-depth analysis to determine the root causes of failures.

Use specific methodologies, such as Cause and Effect Analysis (Ishikawa diagram), the 5 Whys or Failure Mode and Effects Analysis (FMEA), to break down the issue and explore all factors that may be contributing to the failures.

This analysis helps identify not only the symptoms but also the underlying causes, allowing the development of more effective, lasting solutions.

In addition, physically inspecting vehicles and using technical diagnostic tools are crucial to validating the hypotheses developed during analysis.

Continuous review

Failure analysis is not a one-time process, but a continuous one. It is important to implement a continuous review cycle to track the effectiveness of the corrective actions taken and make adjustments as needed.

Continue collecting failure data and performing periodic analyses to identify new areas for improvement and ensure issues do not return.

What methods analyze the causes and effects of vehicle failures?

Cause and effect analysis

Also known as the Ishikawa Diagram or Fishbone Diagram, this method helps identify, explore and visualize all possible causes of a specific failure.

It organizes causes into main categories, such as manpower, materials, methods, machines, environment and measurement. Each category is subdivided to explore possible causes in more detail, making it easier to identify factors contributing to the issue.

The 5 whys method

This is a simple, effective technique for finding a failure's root cause. It involves asking “Why?” repeatedly (generally five times) until the issue's root cause is identified.

This method helps go beyond surface symptoms and uncover underlying issues that may not be immediately apparent.

If a vehicle shows excessive tire wear, the first question might be: “Why are the tires wearing out quickly?” The answer may lead to another question until the root cause is revealed, such as “Tire pressure is not being checked regularly”.

Pareto analysis

This method is based on the Pareto principle, which suggests that 80% of issues are caused by 20% of causes.

It focuses on identifying and addressing the causes contributing to most issues. Using a Pareto chart helps visualize the most significant causes and focus on the issues that will have the greatest impact on improving the fleet.

For example, if the analysis shows that most failures are related to inadequate preventive maintenance issues, efforts can be directed toward improving maintenance processes.

Fault tree

The Fault Tree is a deductive technique using a graphical approach to analyze system failure causes. It starts with a top-level failure (an unwanted event) and breaks it down into all its possible causal events through logic gates.

This is useful for understanding the relationships between different failure causes and visualizing the chain of events leading to the issue.

Also called FTA, it is a method that contributes greatly to analyzing complex failures where multiple factors may be interconnected, allowing detailed understanding of interactions between different vehicle system components.

Maintenance history

A detailed review of vehicle maintenance histories can provide information about recurring failure patterns and their causes.

This retrospective analysis helps identify whether certain components or maintenance practices are contributing to failures and allows maintenance procedures to be adjusted to prevent future issues.

Keeping detailed records of all maintenance performed, including parts replaced, service dates and mileage, allows fleet managers to draw correlations between past events and current failures.

What are the fundamentals of maintaining a freight vehicle fleet?

These points include activities that should be part of your operation's maintenance management routine:

Preventive maintenance: perform regular inspections and services, such as oil changes and fluid checks, to identify and correct issues before they become serious failures.
Tire pressure control: maintain correct tire pressure to avoid irregular wear, increased fuel consumption and blowout risks.
Use of quality spare parts: use original spare parts or those recommended by the manufacturer to ensure durability and safety.
Continuous team training: offer regular training for drivers and technicians on driving best practices, maintenance techniques and correct equipment use to prevent failures.
Maintenance data recording and analysis: keep detailed records of all maintenance activities and use fleet management systems to facilitate analysis and informed decisions.

Keeping vehicles in good condition depends on a routine of maintenance management and vehicle failure analysis.

See how Prolog App solutions can contribute to this, making your daily operations easier and faster. Schedule a free online demonstration.

Frequently asked questions

Where should a fleet failure analysis begin?

With data collection. For each recorded failure, note the vehicle's model and year, mileage, maintenance history and incident details: date, time, location and conditions in which it happened. With this record organized in a management system, the next step is to look for patterns — failures recurring on the same vehicle, in the same period or under similar conditions.

Which methods help identify a failure's root cause?

Methods used include the Ishikawa diagram, which distributes causes into manpower, material, method, machine, environment and measurement; the 5 whys, which repeat the question until the underlying issue emerges; Pareto analysis; the fault tree, or FTA, useful when several factors intersect; and reviewing each vehicle's maintenance history.

What is Pareto analysis applied to maintenance?

It applies the Pareto principle, which suggests a proportion: 20% of causes generate 80% of issues. In a fleet, it is used to discover which causes account for most failures and direct efforts toward them. If the survey shows, for example, that most failures are related to inadequate preventive maintenance, that is the process worth changing first.

Which types of failure occur most frequently in vehicles?

Generally, the most common involve six areas: mechanical (engine, transmission, brakes, suspension and steering), electrical (battery, alternator, ignition, wiring and electronic sensors), tires (irregular wear, punctures, cuts, bulges and pressure loss), cooling (leaks, water pump, thermostat and radiator), braking system (worn pads and discs, fluid leaks, ABS), and steering and suspension (shock absorbers, springs, bushings and ball joints).

Does the analysis end when the cause is found?

No. The guidance is to treat it as a continuous cycle: after applying corrective action, you need to track whether it worked and adjust as necessary. This means continuing to collect data on new failures and repeating the analysis periodically, both to find new areas for improvement and to ensure the issue does not return.

Which maintenance routines support this work?

Five activities should be part of the routine: preventive maintenance, with regular inspections and services such as oil changes and fluid checks; correct tire pressure control; use of original spare parts or those recommended by the manufacturer; continuous driver and technician training; and detailed maintenance records, supported by a management system for analyzing data and making decisions.

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