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Old 06-18-2006, 07:17 AM
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Default AIR BRAKE TEST?

Can anyone give me the steps for doing an air brake test for a Class A? I have had my Class B for 11 yrs but am a little confused about how they want me to do the pretrip air brake to upgrade. I know how to do the test for Class B, is it the same thing but using pushing both knobs in? I failed the pretrip the first time because I didn't pull up and hit the brakes to see if it pulled to one side or the other, which is now an auto fail on the pretrip inspection. Everyone I know around here was grandfathered in and seriously not sure how the test is. Thanx!

Straight Truck Air Brake Pretrip Inspection:

1. Start engine and build pressure to 90-110 lbs
2. To test parking brake with engine running:
A. Apply Parking Brakes
B. Put in gear, then slowly release clutch
C. Vehicle must stay stopped where it is
3. Shut engine down, turn key back on.
4. Charge air system (Push one knob in)
5. Wait for initial fill.
6. Wait one minute for air leakage, rate should be no more then 2 psi.
7. Apply 90 lbs pressure to brakes and hold for one minute.
Air leakage should be no more then 3 psi.
8. Pump Brakes till red light/buzzer comes on ( about 60 lbs)
9. Keep pumping brakes till one knob pops out. (about 20-40 psi) Brakes will set.[/url]
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Old 06-18-2006, 01:29 PM
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Thats right except I was taught 3 psi with brakes not applied and 4 with brakes applied .. I dont imagine that sort of thing varies by state, so double check.
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Old 06-18-2006, 11:29 PM
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Well these are the steps I got from a third party testing center for straight trucks. I am assuming that the psi numbers are correct. I will double check in the new book though. Maybe they are different for tractor/trailer. Thank you.
As far as testing the service brakes (pulling up and hitting brakes to see if it pulls) I am assuming I would do this after step 1 so I am not waisting time on my pretrip waiting for air to build back up...?? They give you 30 minutes for the complete pretrip inspection.
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Old 06-26-2006, 12:00 AM
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Default Re: AIR BRAKE TEST?

Quote:
Originally Posted by Mother_Trucker
Can anyone give me the steps for doing an air brake test for a Class A?
I'm still in school here in MN although I live across the border in WI. I'm going to be taking my test on July 5.

The following are steps they gave us for the Air Loss Test. Hope this helps.

1.) Start the engine to fully charge the air tanks
2.) Place transmission in a low gear, shut down the engine, turn ignition key back to the on position.
3.) Push the tractor parking brake and the trailer air supply buttons in to release brakes and then allow the system to stabilize (watch for needles in the air guage(s) to stop moving).
4.) Apply service brakes and check for one minute to make sure there is no more than 4 psi loss.
5.) Pump service brake (foot pedal) until low pressure warning signal comes on (around 60 psi). You can turn the key off after the warning signal comes on.
6.) Continue to pump the brake until trailer air supply and the tractor parking brake buttons pop out (between 40-20 psi).
7.) Depress clutch, start engine, and check the parking brakes by trying to pull ahead.
8.) Place transmission in neutral, build up air in the system to 120-130 psi.
9.) Push in the tractor parking brake and the trailer air supply buttons, pull down on the trailer brake handle and place the transmission in a low gear and check to see that the 5th wheel is properly connected by trying to pull forward.
10.) With all brakes released, pull forward a few feet, step on clutch, and apply the service brakes to check to see that they are working properly.
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Old 06-26-2006, 12:11 AM
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Default Here's My Version

THE "IN CAB" AIR BRAKE TEST

First thing to do is to break the test down into the different categories! You can do this easily
by using the Acronym L-A-B (Leaks, Alarms, Buttons)

The test is done during the CDL Pre-trip and is one of the last skills the you will do BEFORE you go out on the road for the actual driving or SKILLS test!

Chock the wheels! if you have not yet! Some states will require the truck to be chocked BEFORE you even start the walk around

With the engine still running, check the air pressure. You are looking and or listening for the air systems ?governed cut out pressure? to be reached. This happens when the air tank pressure reaches 100 psi -125 psi. When the "cut out pressure" is reached, you will hear the air compressor stop pumping air (sometimes hard to hear) or you will hear the air dryer exhaust air with a loud PSSSSHHHTTTT!!!! NOW you can start the air brake (L-A-B) test.

ALWAYS be sure to tell the CDL examiner what you're doing, He or She cannot read your mind!

Turn off the engine and TURN THE KEY BACK ON!!

Why? Most trucks low air pressure warning buzzers will not work with the key off!!

The first required task in the L-A-B test is to check for LEAKS

Release ALL the brakes! Push in BOTH brake buttons! (Remember, the truck is chocked so don't panic) There WILL be an initial DROP in air pressure! This is normal and it?s basically the air leaving the tanks and going out to the rest of the system! After this initial drop, watch (and point to) the air gauge and listen for any leaks.

?L? to test for LEAKS:

Push in and HOLD the brake pedal. Tell the examiner what your doing and he/she will be probably be asking you what you're looking for. just tell them that you are holding the brake pedal down for 1 minute and looking for an air loss of LESS THAN 4 psi in that minute. (straight trucks require LESS THAN 3psi).

Make sure you have some way of TIMING yourself!! and that you keep your foot on the brake for the WHOLE MINUTE, IF the examiner sees you are doing things correctly, he/she may declare'; "OK, its been a minute". And move you to the next part of the test.

"A" NOW you will test for ALARMS

Firmly and pretty quickly pump or ?fan? the brake pedal and watch the gauge again, at around 60 psi the ?low air? alarm or buzzer and/or the warning light will come on.

If you forgot to turn the key on the alarms and warning lights will not work! You may FAIL the test right here or you may have to start the WHOLE brake test over again!

"B" The next task is to check the BUTTONS

AFTER acknowledging the ALARMS, Continue to Pump the brake pedal (SLOWER BUT MORE DELIBERATE) until BOTH of the Air supply buttons ?POP? out.
The buttons should "pop" about 30 psi.

After the buttons pop, you will need to start the engine (Ask the examiner if it's OK to continue) and build air pressure. While the air is building, ask the Examiner if you can go pick up your wheel chocks and do so (this is a GREAT time to take a DEEP breath and try and gather your wits). Stow the wheel chock and climb back into the drivers seat, PUT ON YOUR SEAT BELT!! and get ready to finish the brake test.

There are TWO final tests for the brake system

Parking Brakes:

After you build the air pressure back to ?normal? range, The brakes are still set from the air brake test so all you need to do is put the truck in a low gear and attempt to pull forward. Use light pressure! Do not release the clutch fully, you could damage the drive train. A slight ?TUG? against the brakes is what you want.

Service brakes:

To test the service brakes, release ALL the brakes (while covering the foot brake of course) pull the truck into LOW gear, check to see that the area ahead is CLEAR and slowly get the truck moving forward S-L-O-W-L-Y. After you get the truck moving push in the clutch and apply the foot brake, the truck should stop without pulling to either side!. Some states will require you to remove your hands from the wheel for this test.
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Old 06-26-2006, 01:25 AM
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I took the test for the second time @ an actual highway patrol testing station ( not a third party like station like the first time) and PASSED my pretrip and road tests! I know, after 11 yrs, have my Class A! I actually did the parking brake and service brake test after the initial tank fill so I didn't waiste any of my 30 minutes on waiting for the tanks to refill after pumping the brakes down. He did mark down that I didn't wait the full minute, even though I said " hold brake pedal for a minute, listen for leaks and watch that the air loss is no more then 4 psi per minute" but I didn't actually hold it for a full minute, so he marked that wrong. But I did PASS, so thank you all for your help!
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Old 07-02-2006, 08:24 AM
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Congrats Mother_Trucker.

For others contemplating the test be aware that different states have different approaches to the air brake test.

Put in Gear - Take Keys - Get Out and Close Door - Chock Wheels Before You Start


1 ? Governor Cut In and Cut Out
With engine running release brakes (push both buttons in)
Build Air to 120 psi and Fan down to 100 psi
Bring RPM up to just under 1500 and say that cut in works when needle starts to rise.
Keep RPM at 1500 and tell officer that it should cut out at about 120 psi.
Continue to let needle rise and when needle stops tell officer needle has stopped at 120 psi. Cut out works.
Apply the Brakes (pull out both buttons) and shut off engine.
Put key in the ?ON? position.

2 ? Air loss rates (3 psi & 4 psi)
Release Brakes (push both buttons in) and after initial loss of 5 ? 15 psi the system cannot lose more than 3 psi in one minute.
Time it and after one minute say it did not.
Now apply firm pressure to the service brake and after another initial loss of 5 ? 15 psi the system cannot lose more than 4 psi in one minute.
Time it and after one minute say it did not.

3 ? Low Air Warning Alarm (60 psi)
With key in the ON position fan the brake pedal so air drops.
Tell officer that the alarm must come on BEFORE the system drops below 60 psi.
Tell officer that it did when alarm comes on.

4 ? Spring Brakes (Between 20 & 40 psi)
Continue fanning brake pedal dropping air pressure.
Check that spring brakes come on between 40 and 20 psi.
Both buttons will pop out.
Brakes are applied.
Tell officer that they did.

5 ? Rate of Build Up (85 ? 100psi /45sec.)
Start engine and bring RPM to just under 1500 to build up air.
1st Make sure alarm stops after system builds past 60 psi.
Tell officer that alarm has stopped and you will time it from 85 to 100 psi.
Tell him that it must take 45 seconds or less.
When it reaches 85 psi say 85 and timing.
Time rise in pressure from 85 to 100 psi.
Tell officer how long it took. (example: It took 23 seconds.)
Continue to let air build to 120 psi.

Put In Gear. Shut Off Engine. Take Keys. Get Out and Close Door. Get Chocks.

6 ? Test Brakes (Parking and Service)
Only brake on is one you are testing!
Push tractor brake in. Check trailer brakes & fifth wheel connection.
Pull tractor brake out. Push trailer brake in and check Tractor Parking Brake.
Take out of gear and build to 120 psi.
Shift into 2nd gear and drive forward?.Pull down trolley to check trailer brakes.
Push trolley back up to release and while in 2nd gear drive forward at 5 mph.
Use service brake to stop truck.

You should tell officer.
No Unusual Feel to Pedal
No Delayed Stopping
Truck Did Not Pull to Left or Right
No Shudder in Wheel
No Unusual Sounds or Smell

Air Brake Test is Finished.
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Old 10-15-2006, 04:13 AM
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A newbie follow up question on the air brake pre-inspection test:

I guess the answer is yes, but are we supposed to do the air brake test for every pre-trip inspection? Even when it means you are taking off from a packed truck stop at 5am?

Pumping the air brakes to bring down the pressure can be a noisy process, especially when there are sleeping drivers only a few feet away in their trucks on either side. Are there any rules of etiquette in this situation?
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Old 10-16-2006, 10:58 PM
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When holding the brake for one minute, I think so the examiner will time you.
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Old 07-31-2014, 05:50 PM
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what is a passable airloss rate for a truck and trailer?
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