| Copyright © 2006 - 2012 cdldigest.com All rights reserved. ***Please note that CDLDIGEST.COM is not owned by, operated by, or affiliated with any government agency.*** |
NOTE: Information in this section is not all inclusive and is subject to change due to law changes. For
the latest information refer to the current CDL Manual for the state you live in.
the latest information refer to the current CDL Manual for the state you live in.
Pre Trip Inspection Brake Check
Parking Brake Check (Pre Trip Inspection)
Hydraulic Brake Check (Pre Trip Inspection)
Air Brake Check (air brake equipped vehicles only) (Pre Trip Inspection)
Air brake safety devices vary. However, this procedure is designed to see that any safety device operates
correctly as air pressure drops from normal to a low air condition. For safety purposes, in areas where
an incline is present, you will need to use wheel chocks during the air brake check. The proper
procedures for inspecting the air brake system are as follows:
Test Air Leakage Rate (Static check) (Pre Trip Inspection)
With a fully-charged air system (typically 120 psi), turn off the engine, chock the wheels, release (push
in) the parking brake button (all vehicles) and trailer air supply button (for combination vehicles) and time
the air pressure drop. After the initial pressure drop, the loss rate should be no more than 2 psi in one
minute for single vehicles and no more than 3 psi in one minute for combination vehicles.
Test Air Brake System for Leaks (Pre Trip Inspection)
With parking brake, (all vehicles) and trailer air supply button (for combination vehicles) released
(pushed in), apply firm pressure to the service brake pedal. Watch the air supply gauge and listen for
leaks. After the initial pressure drop, the loss rate for single vehicles should be no more than 3 psi in
one minute and no more than 4 psi in one minute for combination vehicles. If the air loss rate exceeds
these figures, have the air system repaired before operating.
Test Low Pressure Warning Alarm and/or Signal (Pre Trip Inspection)
Turn the key to the on position. Rapidly apply and release the service brake pedal to reduce air tank
pressure. The low air pressure warning signal must come on before the pressure drops to less than 60
psi in the air tank. If the warning alarm/signal doesn’t work, you could be losing air pressure without
knowing it. This could cause the spring brakes to activate suddenly. Only limited braking can be done
before the spring brakes come on.
Check That the Spring Brakes Come on Automatically.
Continue to rapidly apply and release the service brake pedal to further reduce air tank pressure. The
trailer air supply button (if it is a combination vehicle) and parking brake button should pop out when the
air pressure falls to the manufacturer’s specification (usually between 20 to 40 psi). This causes the
spring brakes to come on.
Check Rate of Air Pressure Buildup (Pre Trip Inspection)
When the engine is operating at 1800 RPM, the pressure should build from 85 to 100 psi within 45
seconds in dual air systems. (If the vehicle has larger than minimum air tanks, the buildup time can be
longer and still be safe. Check the manufacturer’s specifications.) If air pressure does not build up fast
enough, your pressure may drop too low during driving, requiring an emergency stop. Don’t drive until
you get the problem fixed.
Test Service Brakes (Pre Trip Inspection)
Wait for normal air pressure, release the parking brake and trailer air supply button
(for combination vehicles), move the vehicle forward slowly (about 5 mph), and apply the brakes firmly
using the brake pedal. Note any vehicle “pulling” to one side, unusual feel, or delayed stopping action.
This test may show you problems which you otherwise wouldn’t know about until you needed the brakes
on the road.
Parking Brake Check (Pre Trip Inspection)
- Apply parking brake only and make sure it will hold the vehicle by shifting into a lower gear and
gently pulling against the brake.
Hydraulic Brake Check (Pre Trip Inspection)
- With the engine running, apply firm pressure to the service (foot) brake pedal and hold for five
seconds. The brake pedal should not move (depress) during the five seconds. - If equipped with a hydraulic brake reserve (backup) system, with the key off, depress the brake
pedal and listen for the sound of the reserve system electric motor. - Check that the warning buzzer and/or light is off.
- Check the service (foot) brake operation by moving the vehicle forward slowly (about 5 mph) and
apply the brake firmly. Note any vehicle “pulling” to one side, unusual feel or delayed stopping
action.
Air Brake Check (air brake equipped vehicles only) (Pre Trip Inspection)
Air brake safety devices vary. However, this procedure is designed to see that any safety device operates
correctly as air pressure drops from normal to a low air condition. For safety purposes, in areas where
an incline is present, you will need to use wheel chocks during the air brake check. The proper
procedures for inspecting the air brake system are as follows:
Test Air Leakage Rate (Static check) (Pre Trip Inspection)
With a fully-charged air system (typically 120 psi), turn off the engine, chock the wheels, release (push
in) the parking brake button (all vehicles) and trailer air supply button (for combination vehicles) and time
the air pressure drop. After the initial pressure drop, the loss rate should be no more than 2 psi in one
minute for single vehicles and no more than 3 psi in one minute for combination vehicles.
Test Air Brake System for Leaks (Pre Trip Inspection)
With parking brake, (all vehicles) and trailer air supply button (for combination vehicles) released
(pushed in), apply firm pressure to the service brake pedal. Watch the air supply gauge and listen for
leaks. After the initial pressure drop, the loss rate for single vehicles should be no more than 3 psi in
one minute and no more than 4 psi in one minute for combination vehicles. If the air loss rate exceeds
these figures, have the air system repaired before operating.
Test Low Pressure Warning Alarm and/or Signal (Pre Trip Inspection)
Turn the key to the on position. Rapidly apply and release the service brake pedal to reduce air tank
pressure. The low air pressure warning signal must come on before the pressure drops to less than 60
psi in the air tank. If the warning alarm/signal doesn’t work, you could be losing air pressure without
knowing it. This could cause the spring brakes to activate suddenly. Only limited braking can be done
before the spring brakes come on.
Check That the Spring Brakes Come on Automatically.
Continue to rapidly apply and release the service brake pedal to further reduce air tank pressure. The
trailer air supply button (if it is a combination vehicle) and parking brake button should pop out when the
air pressure falls to the manufacturer’s specification (usually between 20 to 40 psi). This causes the
spring brakes to come on.
Check Rate of Air Pressure Buildup (Pre Trip Inspection)
When the engine is operating at 1800 RPM, the pressure should build from 85 to 100 psi within 45
seconds in dual air systems. (If the vehicle has larger than minimum air tanks, the buildup time can be
longer and still be safe. Check the manufacturer’s specifications.) If air pressure does not build up fast
enough, your pressure may drop too low during driving, requiring an emergency stop. Don’t drive until
you get the problem fixed.
Test Service Brakes (Pre Trip Inspection)
Wait for normal air pressure, release the parking brake and trailer air supply button
(for combination vehicles), move the vehicle forward slowly (about 5 mph), and apply the brakes firmly
using the brake pedal. Note any vehicle “pulling” to one side, unusual feel, or delayed stopping action.
This test may show you problems which you otherwise wouldn’t know about until you needed the brakes
on the road.
| CDL Digest is your source for commercial drivers license (CDL) information and resources, including CDL license study guides, how to get a CDL license, medical and general CDL license requirements, disqualifications, and CDL license endorsements. |
| Commercial Drivers License (CDL) Pre-Trip Inspection: Brake Check |
| CDL Practice Test Study Guide Downloads TITLES AVAILABLE: General Knowledge Air Brakes Combination Vehicles Double/Triple Trailers Hazardous Materials Tank Vehicles Passenger School Bus |
| Pre-Trip Inspection Engine Compartment Cab Check/Engine Start Brake Check External Cab Trailer Double/Triple Trailers Tank Vehicle Coach/Transit Bus |
 |
 |
|
|