fbpx

Cart

The cart is empty

Cannot find your purchased courses? Click here to Login!

As part of your CDL air brake inspection, you must test the tractor protection valve & system.

How to CDL Airbrake Inspection | Tractor Protection System

https://youtu.be/m4S8PSRAuF4

Updated Jan 2021

Closed Caption

The trailer air supply valve is nothing more than an ON/OFF switch.<p>It turns air on and off to the semi-trailer.<p>The subsequent action is that the trailer spring brakes also release and apply.

Introduction

Hi there smart drivers, Rick with Smart Drive Test talking to you today about how to test the tractor protection system.

Any truck designed to pull a trailer with air brakes is going to be equipped with tractor protection system, which consists of the tractor protection valve--just to confuse you [CHCUCKLING] the system and the valve are called the same thing - the tractor protection valve and the red, eight-sided trailer air supply valve on the dash.

Many people think the trailer air supply valve on the dash controls the parking brakes on the trailer, it doesn't.

That's just a subsequent action.

Today we're going to talk to you about how to test the tractor protection system on the truck and trailer.

We’ll be right back with that information.

[OPENING CREDITS & MUSIC]

PASS CDL Air Brakes First Time - take this comprehensive course!

A course for truck, bus & RV drivers operating a vehicle fitted with air brakes.

This self-paced course gives you:

• more than 100 practice test questions with feedback;
• EASY step-by-step instructions how to conduct a pre-trip inspection on an air brake system;
• DETAILED rules to use air brakes and brake downhill with a large vehicle safely;
• step-by-step instructions and precise wording for pre-trip inspection of trailers with airbrakes;
• explained SIMPLY to you is the tractor protection system and its components.

 Illustrations, checklists, & cheat sheets ensure your success 

Cart and Checkout


Prologue

Hi there smart drivers, welcome back.

Rick with Smart Drive Test talking to you today about how to test the tractor protection system on a truck that's designed to pull the trailer equipped with air brakes.

All trucks pulling trailers with air brakes will have a tractor protection system.

As I said in the introduction, the tractor protection system consists of the tractor protection valve and the trailer air supply valve.

So, the first test--there's three test for testing the tractor protection system:

1) the first one is to pump down the air pressure in the system between 20 and 45psi (pounds per square inch) the trailer air supply will pop out, shutting air off to the trailer.

2) the second test is to go out to the trailer to ensure that the parking brakes have indeed applied.

3) If the trailer brakes have applied you come up to the front of the trailer and pull the glad hand off the trailer.

You come into the cab of the truck and make a service brake application.

When the system air pressure is between 20 and 45 psi, the tractor protection valve will tell the trailer air supply to shut off air to the trailer.<p>The trailer air supply will shut off.<p>Above 60 psi, the low-air warning light and buzzer will activate.There shouldn't be any air leaking out through the tractor protection valve.

And that is the third test.

And when the tractor protection system passes those three tests, then you know that the tractor protection system is working on the truck.

The first one here is to pump down between 20 and 45psi to ensure that the trailer air supply shuts off air to the trailer.

Now as I said in the introduction, the trailer air supply does not activate the parking brakes on the trailer - it's a subsequent action.

The Trailer Air Supply Valve

The trailer air supply valve turns air on and off to the trailer – it’s nothing more than an on/off switch.

Think of the trailer air supply like a light switch in your house.

The light switch in your house controls the flow of electricity - it doesn't turn the light off and on.

The light switch controls electricity and subsequently it turns the light off and on.

So if you have a light switch in your house that turns the garage light on and off, you turn the light switch off to turn the electricity off.

And to know that the light in the garage actually went out, you have to go to the garage and check the light went out.

The same thing with the trailer air supply valve that shuts air on and off to the trailer.

You have to go out to the trailer to ensure that the trailer brakes applied, which is the same thing as the light in the garage - you have to go to the light to make sure it actually went out.


Don't Work the Day for Free:: Weigh Scale Checklist 

This checklist will provide you with a list of paperwork that you need to bring into the authorities when you get pulled into the scale house.

DID YOU KNOW? :: Bus & truck drivers are the only public sector that has its own police force (DOT, CVSE, MTO, etc.);

SMART :: There's a lot of paperwork you must produce for authorities at the weigh scale;

SELF-CONFIDENCE :: Bring all paperwork in one hit & impress the diesel bears!

Because in most cases, it's you that gets the fine...NOT the company!

Get Your Driver's Test Checklist Now!


Testing that the Trailer Air Supply Shuts Off Air

And so what we're going to do, we're going to pump down between 20 and 45psi to ensure the trailer supply valve pops out.

The low-air warning has activated and the trailer air supply has shut air off to the trailer between 20 and 45psi.

Now we're going to get out of the truck and go back to the trailer and ensure that the trailer brakes have applied.

When air brakes are applied the pushrod and slack adjuster make an approximate 90° angle.

Testing that the Trailer Brakes Are Applied

So you do is you come back here to check that the trailer brakes have applied.

You simply look under the trailer and see that the slack adjuster and pushrod are making a 90° degree angle, therefore you know the brakes are applied.

It’s an approximate 90° angle.

If the brakes are installed correctly, when applied the pushrod and slack adjuster form an approximate 90° angle.

If it’s not a 90° angle when the brakes are applied, the brakes may not be set up correctly.

There have been some people out there that have said it’s applied and that sort of thing…

When applied the pushrod & slack adjuster make an approximate 90° degrees because it isn't 90° degrees it's not good physics.

And it's just a way the brakes are set up.

So you know that the brakes are applied because the pushrod and slack adjuster form an approximate 90° angle.

Testing the Trailer Air Supply Valve

Now we’re going to go up to the front of the trailer, and we’re going to disconnect the gladhands.

You just remove the gladhands – you don’t have to take the electrical line off.

Just lay the gladhands down here on the deck like that.

Open the door and make a service brake application--you don't have to get in the truck--just with your hands push down on the brake pedal.

There isn’t any air leaking out of the gladhands, therefore I know the tractor protection valve is working properly.

All 3 Tests Indicate...

All three tests indicate that the tractor protection system is working.

The trailer supply valve on the dash shut off air to the trailer between 20 and 45.

The trailer brakes applied and I know that because the pushrod and slack adjuster make a 90° degree angle.

I took the gladhands off and made a service brake application.

There is no air escaping from the tractor protection valve and after I do that I reattach the two lines.

And most of the time, to test the tractor protection system, you're going to be doing this as part of all of your overall in-cab checks.

So you get back in the truck and do your compressor test, maximum build-up, and at maximum pressure you’ll do your leak test.

But this is just tractor protection system that you're testing.

To test the tractor protection valve, remove the gladhands and set these on the deck.<p>Open the door, and with your hand make a service brake application.<p>No air should escape from either the gladhands lines on the truck or the trailer.<p>If no air escapes, the tractor protection valve is functioning normally.

Conclusion

Quick review of testing the tractor protection system.

All trucks designed to pull trailers equipped with air brakes are going to have a tractor protection system.

The first thing you do is chock the wheels on the truck, release the parking brakes, and pump the system air pressure down between 20and 45psi.

The trailer air supply should shut air off to the trailer.

And as I said, it doesn't apply the parking brake, the trailer air supply supplies air to the trailer(s).

It’s just like a light switch in your house that turns the electricity off and on.

The trailer air supply shuts air off and on to the trailer.

After it's shuts air off to the trailer between 20 and 45psi you go out to the trailer and make sure that the trailer brakes have applied.

And you know that because the slack adjusters and pushrod form an approximate 90° degree angle.

You then come up to the front of the trailer and take the gladhands off, and make a service brake application.

If there isn't any air leaking out of the gladhands there, you know the tractor protection valve is working.

And those are the three tests.

And after doing those three tests, you say to the examiner, “all three tests indicate that the tractor protection system is working.”

Question for my smart drivers:

For those CDL drivers doing trailers fitted with air brakes, do you have to test the tractor protection system as part of your license test?

Leave a comment down in the comment section there – all of that helps us out.

I'm Rick with Smart Drive Test.

Thanks so much for watching.

If you like what you see here share, subscribe, leave a comment down in the comment section.

As well, check out all the videos here, check out the videos over here.

All of those will give you great information to those are you going to get a license or starting a career as a bus or truck driver.

Thanks again for watching.

Good luck on your road test.

And remember, pick the best answer not necessarily the right answer.

Have a great day.

Bye now.

BLOOPER

[BLOOPER – STANDING AND SMILING] so just just quick review… testing tractor protection system…tru…

Log in to comment
blog image

Brake Fade | Air Brakes

Author: Rick
Although air brakes are more-or-less buletproof these, like all braking systems, have one failing: BRAKE FADE.
Default Image

Trailer Hand Control (Spike)

Author: Rick
OBSOLETE Independently applies and releases the trailer service brakes. Knowledge Test Question: This air brake control is not to be used for parking. Although most tractors are still equipped with hand valves, beyond a trailer service tug test, these air…
Default Image

Stop Light Switch

Author: Rick
Activates the brake lights when a service brake application is made by the driver.
Default Image

Spring Parking Brake (Emergency)

Author: Rick
Applies the parking brakes of the air brake equipped vehicle indefinitely – if needed of course. The parking brakes are held in the “ON” position by the mechanical force of the springs; these spring parking brakes are held in the “OFF” position by system air…
Default Image

Slack Adjuster

Author: Rick
Slack adjusters have three purposes: 1) To convert the forward linear motion of the push rod into rotary motion of the camshaft. The slack adjuster works on exactly the same principle as a box end wrench on a nut. 2) To act as a lever, thus generating greater…
Default Image

Air Tanks (Reservoirs)

Author: Rick
Stores compressed air for braking and for other air operated accessories. The air tanks are the first fail-safe in the air brake system. In the unlikely event that the air compressor fell of the side of the engine, the air tanks (reservoirs) store enough air…
Default Image

Compounding Air Brakes

Author: Rick
OBSOLETE Making a heavy service brake application while the parking brakes are applied. This is often an error of truck driving school students.
A caging bolt is used to release the emergency brakes in the event of an emergency (life or death situation).

Caging Bolt

Author: Rick
Allows the spring brakes to be manually released in an emergency - a dire emergency.
Default Image

Brake Linings & Drums

Author: Rick
To stop the vehicle, brake linings rub against the brake drum. This action creates friction, converting the vehicle's forward energy of motion into heat energy, which stops the vehicle’s tires. If the tires have traction, the vehicle will come to a stop. The…
Brake fade is the only reason that a modern air brake system will fail.

Brake Fade

Author: Rick
Brake faide is the only reason that a modern air brake system will fail.
Default Image

Air Gauge(s)

Author: Rick
The gauges are in either pounds per square inch (psi) or Kilopascals (kPa). These measure the amount of air pressure in the primary and secondary air tanks.
Default Image

Air Brake Chambers

Author: Rick
Convert air pressure into a strong mechanical force to apply the foundation brakes.
air brake adjustment

Air Brake Manual Adjustment – Pry Bar Method

Author: Rick
Using the pry bar method, confirm that the brake is in fact out of adjustment. After confirming that the brake is out-of-adjustment and it is equipped with a manual slack adjuster, complete the following steps to bring the brake back into adjustment. If one…
Default Image

Compressor or Build-up Test (Air Brakes)

Author: Rick
Depending on which province you're in, the air buildup time or compressor test has somewhat different paramenters. Still, all require that the diesel motor be at a fast idle. A fast idle on a diesel engine is between 900 &1200 rpm.
Default Image

Pry Bar - Check Air Brake Adjustment

Author: Rick
The National Safety Code madates that every driver of a commercial vehicle equipped with air brakes must check push rod travel every day. In many jurisdications, drivers are allowed to use the pry bar method; in others , they must use the applied stroke…
Default Image

Applied Stroke - Check Air Brake Adjustment

Author: Rick
The National Safety Code madates that every driver of a commercial vehicle equipped with air brakes must check push rod travel every day as part of his/her pre-trip inspection. In some jurisdications, drivers must use the applied stroke method; in others, they…

© Smart Drive Test Inc. 2022. Hosted by Cybersalt