Hi there Smart Drivers, Rick with Smart Drive Test talking to you today about how to adjust a manual slack adjusters for the purposes of your CDL license test.
You are watching: How to check slack adjusters on air brakes
You are not going to do this on any modern air brake system, they"re all going to be equipped with automatic slack adjusters.Really Old Trucks
You can see here in the salvage yard I had to walk around here for about a half an hour before I actually found this old probably 1970s maybe early 80"s Ford Louisville that was equipped with manual slack adjusters.
You can tell how old this truck is because it actually says on the hood diesel engine which signifies the transition between gasoline engines and diesel engines.
For big trucks, that happened in the early-70s and that was one of the selling features for this old Ford Louisville and at one time the Ford Louisville actually was the industry standard so it"s a pretty old truck.
So you"re not going to ever have to adjust a manual slack adjuster it"s really unlikely because they"ve gone the way of the dodo bird, but for the purposes of a road test a CDL license test, you"re going to have to do it.
So we"re going to do that today, we"re going to show you how to do it and at some licensing centers here in British Columbia, for example, if you cannot explain how to set up a manual slack adjuster it"s an automatic fail on the air brake portion of your CDL test so you have to be able to do it.
If you go down with a school they"re going to have a vehicle that has a manual slack adjuster on it and you have to demonstrate it or you have to give a verbal.
The driving examiner will just show you a picture of a manual slack adjuster and you"ll have to give a verbal.
So the steps are:chock the wheels,pump the air pressure to over 100 pounds per square inch,release the parking brakes,
get out, determine that it is in fact out-of-adjustment by using the pry bar method for the most part.
You might have to use the applied stroke method and I"ll put a card up in the corner for you here on determining air brake adjustment.
Once you determine that it"s out-of-adjustment you take your 9/16 wrench, push it over the adjusting nut, you"ll have to release the locking sleeve and we"ll show you how to that, and then turn the adjusting nut so the S-cam rotates in the same direction as the brake application.
We"ll show you, that"s key.
Turn the adjusting nut so the S-cam rotates in the same direction as a brake application.
If you turn the nut more than 2 turns and it doesn"t go tight - you"re probably turning it the wrong way!
Then you turn it all the way until the nut goes tight and you shouldn"t have to turn it more than one or two revolutions at the most.
If you"re turning it more than one or two revolutions.
If so, you"re probably going the wrong way.
Turn it until the adjusting nut goes tight, check that it is in fact tight because what you"ve done is manually tightened, or manually applied the brake.
Manually apply the brake, take your wrench, and back it off a third to half a turn, and then make sure that the locking sleeve is re-engaged over the adjusting nut, the 9/16 nut, put your pry bar in and make sure that it"s within adjustment.
After you do that you have to adjust both manual slack adjusters on both sides of the axle so know that as well that if you do one you"ve got to do the one on the other side of the axle as well.
So what we"re going to do today, we"re going to demonstrate how to do that, so stick around, we"ll be right back with that information.
In-Cab CDL Air Brake Checklist
Hi there Smart Drivers, welcome back, Rick with Smart Drive Test talking to you today about how to adjust a manual slack adjuster for the purposes of a CDL license test.
As I said in the introduction, it"s not likely, in this day and age on an air brake system you"re going to find manual slacks - it"s really unlikely.
Now, to get started you"re going to need a 9/16 inch box and wrench, you"re going to need a set of wheel chocks to secure the vehicle against movement, you"re going to need a pry bar if you"re doing the pry bar method, if you"re doing the applied stroke method you"re going to need a measuring device and something to mark the push rod at a fixed position so you can measure how far it comes out of the brake chamber.Dirt Outside the Vehicle
As well you"re going to need a pair of gloves, always wear pair of gloves when you"re working on the vehicle.
That way you can keep the dirt outside of the vehicle when you get into the vehicle you can take your gloves off.
But again, as I said, this is only an exercise for doing a license test and those are the tools that you"re going to need.
Now minimum you"re going to need a hammer, a 9/16 inch wrench, and a pair of gloves and that"ll get you going on being able to adjust a manual slack adjuster.Key Phrases to Say to Examiner to Pass
Now for the most part, on most license tests you"re just going to have to do a verbal and the two key phrases that you say are:
1) I turn the adjusting nut in the same direction as the S-cam Rotates for a brake application.
And we"ll show you how to determine that.
2) As well, we"re going to show you that how to re-engage the locking sleeve over the nut.
That"s the last piece you have to say.
Those are the two key phrases.
And again, I"ll leave a description down in the description box here for a complete written list, checklist, of things that you need to do to adjust a manual slack adjuster.
Find that down in the description box.Determine that the Brake is Out-of-Adjustment
First thing we have to do is we have to push in the locking sleeve on the 9/16 box end we need the adjusting nut so this is the adjusting nut here, you push that in, you can see this goes in fairly easy.
Now you might need a hammer and bang on the box end to get that in.
So the first thing we need to do for adjusting a manual slack adjuster is we put the pry bar on here and we can see that it"s a little bit loose.
Here, actually, I"ll just adjust it.
Adjust it off here a little bit and then you can see that it"s actually out of adjustment.
So we put our pry bar in here and we can say okay that"s out of adjustment.
So the first thing we need to do is we need to put our wrench on here, push the locking sleeve in, and then we turn it so that the S-cam rotates in the same direction as the brake application.
So the way that we determine that is the push rod extends this way out of the brake chamber and we think of it like a wrench on a nut so this is coming out so we turn it this way.S-cam Rotates in the Direction of Brake Application
So the S-cam has to rotate in this direction when we"re turning the adjusting nut.
So this is the only piece, when we turn this adjusting nut here, this S-cam-- the end of the S-cam right here-- is the only thing that should rotate.
So we put our 9/16 wrench on the adjusting nut, when we turn that we can see that the S-cam is rotating in this direction, the same as the wrench on the nut, this way here.
So we put that on there and we turn the adjusting nut until it goes snug, so it"s snug so we take it off, we get our pry bar, we put it in at the clevis pin here and we try and pry the push rod out of the brake chamber.
And it doesn"t come out.
So that means that we"ve manually adjusted the brake.
So now we put the wrench back on at 90° degrees this way.Back Off 1/2 - 1/3 Turn
And we want to go back a quarter to a half a turn.
So we come back just a little past a quarter turn, we make sure that the locking sleeve comes out, and it has in fact.
We put our pry bar back on, and we make sure half to three quarters.
Locking Sleeve Re-Engages
So we can see that it is now in fact adjusted.
So this locking sleeve does not fully encase the adjusting nut on here.
Most of them do but this one doesn"t for whatever reason, so we can just try and move that a little bit, and sometimes you can tap the end of the bolt too and that will bring the adjust, the locking sleeve out over the adjusting nut but this has to be fully engaged over the adjusting nut and that"s the last thing that you say to the examiner is, I would ensure that the locking sleeve is engaged over the adjusting nut.
Because if it"s not engaged it"s just going to go out of adjustment again.
So after you finish adjusting this one you go over the other side.
So again, quickly, pry bar, make sure it"s out of adjustment, this way here, we figure out which way the S-cam rotates for brake application think of it like a wrench on a nut.
So the push rod extends this way, therefor it"s going to rotate in this direction.
In a counterclockwise direction, so we put our 9/16" wrench on the adjusting nut and we turn that until it goes tight and we can see that this S-cam is rotating in a forward motion towards the front of the vehicle which is the correct way.
The adjusting nut has gone tight, we check to make sure that the push rod will not extend out of the brake chamber, because we"ve manually applied the brake, which it has and now we take the adjusting nut and we crank it back a quarter to a half a turn.
So we just go past a quarter of a turn there, we make sure that the locking sleeve is re-engaged, and we make sure that the push rod is within adjustment, and it is within adjustment which is the width of our thumb nail and that"s how you adjust a manual slack adjuster.Conclusion
Quick review of manual slack adjuster, as I said, for the purposes of a CDL license test you"re going to have to do this but for actually adjusting of a manual slack on a modern air brake system it is very very unlikely that you"re going to have to do this.
As I said, Coldstream Truck Parts here in Vernon, I walked around this yard here for a good half an hour before I found this old Ford Louisville that actually had manual slacks on the front of it that I could demonstrate to you how to adjust up a manual slack.
And know as well, here in British Columbia, and some other jurisdictions, if you cannot explain or demonstrate how to do- how to adjust a manual slack adjuster that"s an automatic fail on your air brake.
So just know that as well.
In some cases you"re going to have to give a verbal especially if you don"t have a vehicle that doesn"t have manual slacks on it.
If you"re going with a training truck there"s a good chance it"s going to have manual slacks on it that you can demonstrate that, but for most part you"re going to do a verbal.
Tools To Adjust Manual Slack Adjuster
So the tools you need when you"re doing the pry bar method, you"re going to need a pry bar, you"re going to need a pair of gloves, you"re going to need a hammer, and you"re going to need a 9/16" inch box and wrench.
All manual slack adjusters have an adjusting nut that is a 9/16" adjusting nut, so you"re going to need a 9/16 box and wrench to adjust up the manual slack adjuster.
So the first thing you do, chock the wheels and ensure that you have system pressure over 100 pounds and release the parking brakes on the unit.
Review of Procedure
Then you come out, you determine that it is in fact out of adjustment, you determine which way the S-cam has to rotate to make a brake application, think of it like a wrench on a nut.
So you just, whichever way the push rod extends out of the brake chamber just follow that around and that"s the direction that the, you"re going to turn the adjusting nut so the S-cam rotates in the direction of the brake application as you saw here when we did this one here.
So you release the locking sleeve over the nut, turn the adjusting nut so the S-cam rotates in the same direction as the brake application, turn it until it goes tight, if you turn it more than one or two full revolutions you"re probably going the wrong way.
So once it goes snug then you take your pry bar, pry on the push rod, it should not extend out of the brake chamber because you"ve manually applied the brake, and then at that point you take the adjusting nut and you back it off a quarter to a half a turn.
Usually just about a third is really good, that"s generally the best.
So you back it off, make sure the locking sleeve re-engages and then take your pry bar and make sure that it"s within adjustment and if you"re doing the pry bar method it shouldn"t come out of the brake chamber more than the width of our thumb nail.
Adjust Both Brakes Across the Axle
And then finally, if you do one on one side of the axle you"ll have to go over and do the other one on the other side of the axle.
So that"s how you adjust a manual slack adjuster for the purposes of a CDL license test.
Question for my Smart Drivers:
After you got your CDL license have you ever adjusted up a manual slack adjuster?
Leave a comment down in the comment section there, all of that helps out the new drivers working towards getting their CDL license.
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Check out all the videos here on the channel if you"re working towards a license or starting a career as a truck or bus driver.
Lots of great information here, as well, head over to my website, awesome information over at my website and tremendous online courses that you can purchase.
As well, the air brake course is available over there that you can purchase and take.
And in May 2017 we"re bringing out Air Brakes Explained Simply, it updates the forty-year-old air brake manuals in North America that are currently in circulation as well it has 100 multiple choice questions that you will find on a CDL license exam.
So look for that in May 2017.
See more: How Many Inches Is 154 Cm To Inch, Convert 154 Centimeters To Inches
I"m Rick with Smart Drive Test, thanks very much for watching, good luck on your road test, and remember, pick the best answer, not necessarily the right answer.