Roughly 26,400 vehicle accidents each year are caused by faulty brakes.
Fortunately, it's simple to avoid ending up as one of those statistics. As you drive a truck, bus, or similar heavy-duty vehicle, federal CDL laws require routine checks for signs of air brake system malfunction or poor performance.
If signs indicate a potential problem, it’s equally straightforward to troubleshoot and find the underlying issue. That said, straightforward doesn’t necessarily mean “easy.”
In this guide, the experts at Point Spring & Driveshaft Co. walk you through different methods of air brake troubleshooting step-by-step. Then, we offer insights into how you might solve different problems once they're identified.
When To Start Air Brake System Troubleshooting?
It’s important to begin troubleshooting at the very first sign your brakes might have a problem. This is both important for safety and cost-efficiency. Often, catching a problem earlier makes solving it less expensive.
11 Signs Your Truck’s Air Brakes Are In Trouble
If you see any of these eleven signs, it’s wise to start troubleshooting your air brake system.
The brake warning light on your dashboard is on
Your break’s response lags
The brake feels “soft,” easily pushed to the floor
Brake is “locked,” doesn’t respond to pressure or release
Squealing, clinking, or grinding brake sounds
Unexplained vibrations
Truck veers to one side
Air pressure takes too long to build up after the truck starts
Gauge shows low or losing air pressure
Inconsistent brake force or brake pressure
There’s a “burning” smell during or immediately after braking
What Causes Air Brake Issues? 10 Common Culprits
Air brakes can lose functionality for a number of reasons. If the system’s components are the wrong type, ill-fitting, or misaligned, leaks and corrosion will spring up. If any parts become damaged or contaminated, or if the system isn’t well-lubricated, air brakes can start malfunctioning.
To troubleshoot effectively, it's vital to inspect your air brake system for signs of the ten most common causes of air brake issues.
Misalignment
Wrong-size components
Insufficient lubrication
Ungreased or under-greased camshafts, slack adjusters
Too much friction causes components to both “seize” and overheat
Leaks
Damaged or inappropriate seals, gaskets
Punctured or damaged diaphragms within brake chamber
Cracks in air lines
Loose, corroded, or faulty fittings / components
Other component wear and tear, corrosion
Insufficient air compression
Overheating
Decreases necessary brake pad friction
Warps brake drums
Brake shoe jam
Shoe component stuck in “partially applied” position within drum
Air tank contamination
Typically contaminated by oil, grit
This can sometimes be swiftly resolved through alcohol drying
Troubleshooting: Determine The Root Cause of Air Brake Issues
To resolve air brake dysfunction, first diagnose the core problem. Prepare to assess the vehicle’s:
Service Brake System
Parking Brake System
Emergency Brake System
To ensure nothing is missed, experts typically use model-based or data-driven fault diagnostic methods. Often, both methods are used as-needed.
In practice, this can mean both engaging in manual best practices, like measuring the push-rod offset by hand, while simultaneously using best-in-class digital tools to gather and analyze data.
Both diagnostic strategies have a lot to offer. Here’s how our experts approach these two, distinct methods.
Model-Based Diagnostics
Model-based diagnostic methods determine the source of a problem by using a model of the vehicle’s air brake system’s standard or expected behavior (i.e. function, flow). A technician both visually inspects and tests each aspect of the system, comparing and contrasting it with the model.