How To Do A Proper Pre-Trip Inspection, Part 1

So, You've got the permit, learned how back that monster of a truck up, and it's test day at the DMV. Most states require that you perform a pre-trip inspection, or be able to recite the pre-trip inspection procedure by memory. In Mississippi, you do the air brake check, by memory first, and then you move onto the pre-trip inspection.

So, in this article, I'm going to give you a handy Pre-Trip Photo, and explain items and procedures to checking your truck that will make it easier to learn for first timers. Into more detail so that you grab every possible point on the test. I'll also go over what the purpose of a pre-trip inspection is, and how to condense the total inspection into a detailed, swift procedure.

So, we're starting first with air brakes. Unlike a regular vehicle, tractor trailers are equipped with air brakes, air brakes can effectively stop a large trucks, trains, buses, etc.

Air brakes require three stages, which are:

1. Charging: The system must be pressurized with air before the brakes will release. At rest, the brakes remain engaged. Once the system reaches its operating pressure, the brakes are freed and ready to use.
   
2. Applying: As the brakes are applied, air pressure decreases. As the amount of air decreases, the valve allows air back into the reservoir tanks, while the brakes move to the applied position.
   
3. Releasing: Once the brakes are applied and the air escapes after braking, the increased pressure releases the brakes.

Now, that we've decided we want working brakes, this is how to test them:

1. Start Truck
2. Let Air Pressure build 120 - 125PSI
3. Turn Truck Off,Get out chock the wheels.
4. Turn Ignition on, To Supply Power To Dashboard Warning Lights.
5. Release The Parking Brake, You shouldn't lose more than 2PSI per minute.
6. Apply The Service Brake, You shouldn't lose more than 3PSI per minute.
7. Turn Off Engine, Leave Ignition On.
8. Fan Service Brakes.
9. On or Before 60PSI, Low Air Warning indicator MUST come on.
10. Continue to Fan Service brakes.
11. At 40PSI, The Tractor Protection Valve MUST close. (Indicated by the Red 8-sided knob popping out)

In Part 2, I will go over how to Pre Trip the rest of the truck.

Continue To Part 2