Learn how to adjust a manual slack adjuster for your CDL Air Brake Test - watch the video!
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 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.
For Some Tests You MUST Know how to do this
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.
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