Automatic slack adjuster maintenance/adjustment

Problem is someone tells you one thing,and then...well you know.
step by step pti brake adjustment please?(channeling HeavyD) LoL

Guess what WEEK it is,"Whoot Whoot"

 

Go to Youtube and search automatic slack adjuster, there are many good videos. You kinda have to find a make of slack that matches what you have. I also recommend to go to the manufactures websites and look there too for their recommended procedure. Many States and Provinces have specific guidelines and laws about brake adjustment inspection and the actual adjustment. In Ontario, drivers are allowed to adjust manual slacks only if they have the certification. Drivers are technically not allowed to adjust automatic slack adjusters. Only licensed techs are allowed, and this is because, technically automatic slack should never need adjustment and if they do there is something wrong. There are some types, such as the Haldex Self adjusting automatic slacks, (S-ABA series) with the control arm and anchor bracket that if they are out of adjustment, something IS wrong. Adjusting these manually will usually result in out of adjustment brakes within only a few brakes applications!!! Other types such as Meritor are very popular and are out of adjustment simply because they haven't stroked enough with enough pressure to trigger the ratchet mechanism. When you get in your truck, build up the air, release your brakes, (make sure your truck cannot move). It is hard to hear with the engine running, shut it down if you like. Push the brake pedal right to the floor. You are making a 100% full brake application. Every once in a while you will hear POP, or SNAP, this the ratchet mechanism advancing on a Meritor style, they can be rather loud. Kinda like when you get up in the morning, stretch, and you hear snap, crackle, pop in the old bones.
Manufactures used to, (don't know if they still do) recommend that once a year the auto slacks be removed and torn apart, cleaned, repacked or rebuilt as needed and reinstalled for service. In 20 years, I have never done or heard of this being done. I would guess some older auto slacks may be grungy inside and that may prevent proper auto adjustment, and so perhaps they are due for rebuilding, (cheaper to replace.)

 

California allows a driver to adjust his own slack adjusters, as I witnessed when in the scale getting my OD permits looked over. Guy with the last name of Patel (no kidding) got OOS due to brakes, was told by the officer "I dont care if you adjust them, or anyone else, as long as they are within adjustment before you leave here". Kind of surprised me, but I do my own regardless of what anyone else says. Worked for the past 22+yrs for me, so will carry on.

Martin

 

Oh yah, for sure, better to have a safe truck that is rolling making money!!! Totally agree. Just to CMA I have to be legal with my recommendations to you guys. Not looking to get anyone, including myself, into trouble!

 

Thank you HeavyD , I actually do that. I'm going to find out which ones i actually have today,just to be sure. Always appreciate your input!!!!

 

Once a day for a full brake application is plenty to keep them in adjustment. It's really only needed for the tractor in most cases (unless you don't have spring brakes on the trailer). The tractor may only have 1 drive axle with spring brakes and never on steers, so they need a good push once in a while. Any axl with spring brakes gets a good hard push everytime you set the brakes.

Compounding isn't a problem unless you have a really old truck. All have anti-compound valves now, so the service brakes do not add to the spring brakes.

 

Don't rely on the maxi's for setting automatic adjusters. Maxi's parking brake springs have an equivalent brake force of about 60 psi. Auto slacks need about 90 psi.

 

Haldex slacks really need less psi than your valves cracking pressure to adjust. Even 5 psi will give 150 lbs of braking force with a 30 chamber, which is about what it takes to release the adjusting clutch in a Haldex. That is all the force required to make a Haldex adjust. Actaul force to release the clutch varies with slack length, but it's no more than 10 psi. I can release the clutch on a new slack by pushing on it, and I'n not a big guy. The problem comes in when dirt, lack of lube, water contamination, etc. causes the clutch to stick. That's where a quick hard stab on the brakes once in a while helps keeps things free and moving. It's not the force applied as much as the shock that helps. I have had few few slack issues on drive and trailer axles. Not many on steers either, but more than other axles. Steer brake wear slower and there is no spring brake. The vast majority of slack problems comes from improper pushrod length or worn cam bushings. Slacks are often blamed, but they cannot work properly if they are set up wrong or other parts are worn out.