• Pass CDL License
• CDL Air Brakes

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.

Turn the adjusting nut so the S-cam rotates in the same direction as a brake application. In other words, you're manually applying the brakes.

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.

If you don't say these two phrases to the driving examiner, you will NOT pass the air brakes' module of your driving test.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.

All manual slack adjusters require a 9/16" inch box end wrench to adjust.

Manually Apply the Brake

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.

When turning the adjusting nut on a manual slack adjuster to manually apply the brake, the S-cam must rotate in the same direction as a brake application.

Check That Brake is Applied

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.

Before starting any work on a vehicle, ensure that the wheels are chocked so that it doesn't roll over you and kill you!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.

Step-by-step instructions to adjust a manual slack adjuster.

Review

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.

You will need gloves, a hammer, 9/16" inch box end wrench, and a pry bar to adjust a manual slack adjuster on an air brake system.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.

Coldstream Truck Parts in Vernon, BC provided the old Ford Louisville Truck that made this manual slack adjuster demonstration possible.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:

• Pry Bar

• Gloves

• Hammer

• 9/16" inch box and wrench.

Depending on your test center, you will either have to do the pry bar or the applied stroke method to determine if the brakes are in adjustment.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.

Smart Points to Remember

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.

Unless you're driving a really, really old piece of equipment, it's not likely that you'll ever encounter manual slack adjusters on an air brake system.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.

After you got your CDL license have you ever adjusted up a manual slack adjuster?If you like what you see here share, subscribe, leave a comment down in the comment section, as well, hit that thumbs up button!

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.

LEARN MORE

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.

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.

Have a great day, bye now.