Top 5 Common Failures During DOT Inspections (And How to Prevent Them)

Regarding DOT inspections, preparation is key to keeping your diesel truck roadworthy and avoiding costly delays. Even minor oversights can lead to significant failures during inspections, from brakes to lighting. Let’s break down the five most common failures and provide actionable tips to help you stay ahead of the curve.

1. Brake System Violations

Ah, brakes—the backbone of safety for any diesel truck. Unfortunately, brake-related violations top the list of DOT inspection failures. Common issues include worn brake pads, maladjusted slack adjusters, and air leaks in the brake system.

Prevention Tips:

• Conduct regular brake inspections, focusing on air compressors, slack adjusters, and S-cam mechanisms.
• Keep an ear out for air leaks or hissing sounds in the system.
• Measure pushrod travel to ensure it’s within the legal limits (typically under 2 inches for most setups).
• Replace worn brake shoes or adjust them before they reach critical wear levels.

2. Tire and Wheel Infractions

DOT inspectors won’t miss a thing when it comes to your truck’s tires and wheels. Common failures include low tread depth, mismatched tire sizes, or cracks in the rims.

Prevention Tips:

• Maintain a minimum tread depth of 4/32-inch on steering tires and 2/32-inch on all other tires.
• Check tire pressure weekly using a calibrated gauge. Uneven pressure can lead to accelerated wear.
• Inspect for sidewall damage, cuts, and punctures, and replace compromised tires immediately.
• Look for cracks or loose lug nuts on your rims during pre-trip inspections.

3. Lighting System Failures

Non-functional lights may seem trivial, but they’re a major DOT inspection red flag. Burned-out bulbs, missing reflectors, or dimmed lighting can all result in a failed inspection.

Prevention Tips:

• Test headlights, taillights, brake lights, and turn signals every day before hitting the road.
• Inspect reflectors and reflective tape to ensure visibility at night or in poor weather conditions.
• Replace bulbs with high-quality LED options for better durability and brightness.
• Clean light lenses regularly to remove dirt and grime that can reduce visibility.

4. Defective After-Treatment Systems

With stricter emissions regulations, after-treatment systems like the Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) have become common failure points during inspections. A malfunctioning system can result in hefty fines and downtime.

Prevention Tips:

• Monitor the DPF regeneration cycle and perform a forced regen if needed to prevent clogging.
• Use high-quality Diesel Exhaust Fluid (DEF) and refill it regularly.
• Have sensors in the SCR system calibrated to avoid misreading NOx levels.
• Clean or replace your EGR cooler if soot buildup compromises performance.

5. Leaking or Worn-Out Hoses and Lines

Hydraulic, coolant, and air hoses often fly under the radar until they fail. Inspectors, however, will spot cracks, leaks, or improperly secured lines quickly.

Prevention Tips:

• Inspect all hoses and lines for leaks, cracks, or abrasions during pre-trip checks.
• Ensure clamps and fittings are secure to prevent vibration-induced wear.
• Replace coolant and air hoses at regular intervals per the manufacturer’s recommendations.
• Keep spare hoses in your truck to avoid breakdowns in remote areas.

Bonus Tip: Document Your Preventive Maintenance

Failing to keep up-to-date maintenance logs is a sure way to flunk a DOT audit. Keep detailed records of all repairs, inspections, and replacements to prove your compliance.

Conclusion

Staying compliant with DOT regulations doesn’t have to be stressful. You can pass inspections with flying colors by addressing common failure points like brake systems, tires, and lighting. Remember, preventive maintenance isn’t just a legal requirement—it’s the lifeline of your truck’s performance and safety.

If you're in Fredericksburg, VA, and need help preparing for your next DOT inspection, contact the team at Liberty. Whether routine checks or emergency repairs, keeping your truck compliant and road-ready is worth every penny.