Air brake problems: what fails inspections and how to catch it first

Every August, inspectors across North America run Brake Safety Week. In 2025 they inspected 15,175 commercial vehicles and placed 2,296 of them out of service for brake violations. That's about 15 percent, or roughly one truck in seven.

The single biggest reason? Brakes out of adjustment. Inspectors pulled 1,199 vehicles off the road for that alone, more than any other brake problem. And it's one of the easiest to catch before it costs you.

How air brakes go wrong

Air brakes don't usually fail all at once. They drift. Linings wear, slack adjusters stop doing their job, a hose chafes against the frame, a fitting starts to weep. Each one is small. Stack a few together and you've got a truck that takes noticeably longer to stop, or one that pulls hard to one side with a full load behind it.

Symptoms worth stopping for

• Air pressure builds slowly. The compressor should get you from 85 to 100 psi within about 45 seconds at fast idle. If it's taking a lot longer, you've got a leak or a tired compressor.
• You can hear air. A steady hiss with the brakes released or applied is a leak. Find it with soapy water around fittings and chambers.
• The pedal feels different: spongy, low, or needing more push than yesterday.
• The truck pulls to one side when you brake. One side is doing more work than the other.
• The low-air warning comes on while driving, or doesn't come on during your test.
• Pushrod travel looks long. If the pushrods on one axle stick out noticeably farther than the others with the brakes applied, that brake is out of adjustment.

The check that takes five minutes

Your daily air brake check catches most of this. Done right, it covers:

1. Governor cut-out and cut-in pressures
2. Air pressure build-up time
3. Air loss with brakes released and with brakes applied
4. Low-air warning activation
5. Spring brakes setting on their own as pressure drops

Do it every morning, not just when someone's watching. It's the same check an inspector will run, and it's a lot cheaper to fail it in your own yard.

About automatic slack adjusters

Automatic slack adjusters are supposed to keep brakes in adjustment by themselves. When a brake keeps going out of adjustment, the fix is not to keep cranking it back manually. That's covering up a problem with the adjuster, the cam, the linings or the drum, and the brake will drift back out. Get it looked at.

What we do

When a truck comes in with a brake complaint, we check the whole system: compressor output, governor, air dryer, lines and fittings, chambers, slack adjusters, pushrod stroke, linings and drums. You get a straight answer on what's wrong, what it costs, and what can wait, so you can make the call.

If your truck is losing air or pulling to one side, don't push it to the next town. Call us at the number below, and if it isn't safe to drive, our towing partner can bring it in.