Finding Potential Breakdowns during your Pre-Trip Inspection

pre trip inspection

As required by law and for the safety of fellow motorists, all commercial truck drivers are required to perform a pre-trip inspection before starting their hours of service. Failure to do so can lead to DOT fines, violations, and a lower CSA (Compliance, Safety, Accountability) score

However, a proper pre-trip inspection serves another important purpose: To prevent truck breakdowns that can lead to significant financial and liability issues

Of course, it’s not uncommon for drivers to gloss over the pre-trip inspection when trying to meet tight deadlines, overconfidence in the current state of their vehicle, or simply viewing it as a nuisance.

In this article, we will take a look at the following aspects of a pre-trip inspection to avoid truck breakdowns:

  • Semi-Truck Exterior
    • Under the Hood
    • Current Condition of the Tires
    • Lights
    • Brakes
    • Coupling
    • Trailer
  • Semi-Truck Interior
    • interior lights
    • turn signals
    • ABS light
    • gauges
    • windshield wipers
    • horns

The Exterior of your Semi Tractor

The main purpose of the pre-trip inspection is for the commercial truck driver to verify the exterior of the tractor and trailer to assess their roadworthiness.

As you walk around, use your senses to detect any developing issues. For instance, your sense of smell can detect any harsh odors that come from failing brakes. Similarly, you can visually verify if your trailer has started to lean – a sign that your load has shifted or a suspension problem has occurred.

Let’s take a look at what to look for when inspecting the exterior of your truck.

Under the Hood

Start with the least-often checked part of the pre-trip inspection: Under the hood.

Every pre-trip inspection should begin at the front of the vehicle, but first by checking underneath the front of the truck for any leaking fluids. If you notice something, it’s your job as a commercial truck driver to diagnose any problems.

Next, check under the hood to check fluids and mechanical components for signs of immediate repair.

Fluids to check under the hood include:

  • Oil
  • Coolant
  • Fuel
  • Diesel exhaust fluid (DEF)
  • Power-steering fluid
  • Windshield washer fluid

Components under the hood should be evaluated for any cracks, bends, leaks, or mechanical failures. Components to examine when performing a thorough evaluation of the truck’s engine compartment include: 

  • Oil fill tube
  • Fuel caps 
  • Alternator (belt and wires)
  • Water pump
  • Radiator and hoses
  • Fan shroud and blades
  • Frame
  • Turbo
  • And more

If you discover any issues, it is time to find a nearby truck repair shop or call roadside assistance to safely transport your vehicle.

Current Condition of your Semi Tires

Tires are the most common form of breakdown commercial truckers experience.

During your pre-trip inspection of your tires (truck and trailer), take notice of the following signs that you may need to repair;

  • Deflation
  • Punctures/gouges
  • Balding
  • Bubbles 
  • Debris
  • Melting
  • Embedded nails/screws
  • Uneven wear
  • Loose lug nuts
  • Leaks from the hub oiler

If you notice a developing problem, it is better to address the issue by finding a truck repair shop than wait for it to leave you stranded on the side of the road. Keep in mind that the minimum tread depth for semi trailer tires and drive tires is 2/32nd’s. Also, the minimum tread depth for your semi truck’s steer tires is 4/32nds. These regulations are found in the section 393.75 (c).

Tip: If you’re at the minimum tread depth on a steer, consider replacing it and keeping the off tire to use as a spare on your trailer or drive tires.


Your lights are responsible for helping you see the road adequately and to be seen by other drivers in low-visibility conditions.

Check the following lights:

  • Headlights
  • High-beams/fog lights
  • Turn signals
  • Hazard lights
  • Brake lights (tractor and trailer)
  • Side lights

Replacing lights is generally a simple repair. However, lights that are out or intermittent may indicate a short circuit, which can lead to fire or serious electrical malfunction. Remember “Not damaged, cracked, missing, or broken” that was drilled into our heads in CDL training!


Properly functioning brakes means the difference between life and death, so it’s important to verify if they are all in good working order.

To verify the condition of your brakes, do the following:

  • Pay attention to any harsh brake smells (especially after long drives through steep grades)
  • Make sure that the brake system is not leaking any fluids.
  • Perform a static brake check (maximum air loss of 3psi over 1 minute). Listen for any hissing that may indicate pressure loss.

Jake brakes obviously can’t be tested during the walkaround, but should be noted in your evaluation for later repair.


During your pre-trip, ensuring the coupling system is secure is absolutely necessary for safe operation. By looking for flaws in the coupling system, you can prevent a serious accident due to mechanical failure ahead of time.

The most important parts of the coupling system to evaluate include:

  • Fifth wheel (sliding fifth wheel locking pin)
  • Kingpin
  • Glad hands
  • Locking jaws
  • Air lines
  • Apron
  • Clearance
  • Electric line
  • Gap
  • Mounting bolt
  • Platform
  • Release arm
  • Skid plate

It’s also an unfortunate reality that some individuals pull the locking pin or deploy the landing gear to “haze” newer drivers, so double-check before hitting the road.

Checking your Semi Trailer

Trailers are subject to the most abuse on the road and in the yard, so it’s essential to verify the condition of the trailer. A faulty trailer can lead to severe accidents, damaging your cargo, or losing the load. Also, choosing to drive with a defective trailer can lead to expensive tickets if you’re caught at the weigh station or by law enforcement officers.

Look for any mechanical flaws that may hinder the trailer’s ability to remain securely mounted and attached to the tractor, including cracks, bends, or breaks in the following trailer components:

  • Headboard (should be no holes or missing rivets)
  • Landing gear
  • Frame
  • Crossmembers
  • Tandem frame and release pins
  • Release handle and locking pins
  • Rear door and hinges

Also, look for gashes in the side of the trailer that might let moisture, pests, heat/cold or other contaminants in while you drive. If you discover any issue, you may have to call the transport company/broker to iron out any potential delays and issues for liability.

Leaning Trailers

Even if your trailer is mechanically sound, your load may have shifted during transport. A leaning trailer will cause issues in the future and severely weakens your truck’s wear on your tires and suspension.

Make sure that your vehicle is parked in a level surface. While looking from the front and the rear, see if the trailer is leaning to one side or another. If you feel that your load has shifted even slightly, it may not be safe to drive, as leaning can become worse and damage the unsecured cargo in the trailer.

A leaning trailer can be indicative of several dangerous mechanical and other issues:

  • Flat/damaged tires
  • Deformed or broken suspension
  • Twisted chassis
  • Binding shock absorber
  • Faulty torsion bar
  • A Shifted Load

Experiencing a load shift is detrimental to your wallet. Specially for owner operators. The cost of getting a load shift corrected can be costly. Depending on how bad the load has shifted, if its palletized or floor loaded, prices can creep into the range of $2000 or more.

Interior Pre-Trip

Before switching your HOS to “on-duty driving”, the last part of the pre-trip inspection involves the interior of your truck.

  • Perform a “safe start” by checking:
    • interior lights
    • turn signals
    • ABS light
    • gauges
    • windshield wipers
    • horns (optional for populated areas)
  • Check the three (3) emergency devices:
  • Spare electrical fuses
  • Fire extinguisher
  • Three (3) Reflective triangles
  • Ensure that there is no debris/loose objects on the floorboard.
  • Properly adjust all mirrors and windows (no obstructions on the windshield)
  • Put the seatbelt on and check that there are no defects in the belt.
  • Make sure that the shifter and splitter are functioning normally.

Final Word: Trust Your Gut

The pre-trip inspection is very important for safety, but it should supplement your experience behind the wheel. For example, if you noticed that the truck steers slightly in one direction, it might be your alignment – an issue that can be difficult to diagnose during the walk around.

The truth is that your intuition as a commercial driver can help diagnose issues before they occur. If you feel something is wrong but hasn’t shown any verifiable signs, you may want to take some preemptive repairs and routine maintenance at a qualified truck repair shop.

By performing thorough pre-trip inspections, you can stay on the road longer and keep everyone safer.


Tom Senkus is a NY-based freelance writer and former OTR commercial driver. Tom enjoys sharing his knowledge to make the world a better place.”

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