Broken slack adjuster

[lostagain]

The bus is up on blocks in my shop. Take the wheels off yesterday for my annual wheel end service. I am replacing the axle seals because 2 of them have started leaking recently. I discovered one rear brake is not on, as it should be with the parking brake on, what the f... After scraping the grease and dirt off the slack adjuster (automatic), I found the adjusting clutch arm is broken. So it is no longer self adjusting, and is not pushing the shoes tight onto the drum anymore. A few weeks ago, I had to make a fairly hard stop for a traffic light, in the rain, and the opposing side wheels locked up. I didn't think too much of it at the time, just thinking that it was slippery with the rain. But I realize now I have been driving minus a brake since.  This emphasizes the importance of an annual service, meaning taking the wheels off to have a good look, and adjust and grease, etc. Not possible otherwise with a highway coach to do,  like it is on a truck where everything is readily accessible. I am going to replace them with manuals, like I did at the front a couple of years ago. I like manual slacks better, being the only driver and mechanic on the bus. 

So fellow busnuts, a good wheels off inspection once a year is a wise thing to do, either yourself, or by a good shop.

JC

[bevans6]

As you replace it, remember that your bus came stock with manual adjusters on both front and rear, while auto adjusters were an option.  On the other hand, I can't imagine adjusting manual adjusters with any sense of accuracy with the wheels on without a pit.  I have auto's on the rear, and I have licensed mechanics that I trust inspect them annually, and I have Bendix manual on the front, brand new (from Luke).   When I bought my bus it had to pass a provincial dot inspection and had a full brake job as part of the sale agreement, yet one front slack adjuster was indeed broken - the locking ring that locks the adjusting bolt was missing and the bolt could spin freely.  A large part of my ongoing mission to learn everything about air brakes was born the day I found that one. 

Brian

[lostagain]

Brian, so true. I feel the same way about the so called professionals. That is why I do all my own maintenance and repairs on my vehicles. Why pay $120/hr for an apprentice to learn on my stuff, and screw it up? I can do that myself, LOL. I enjoy fixing it myself anyway.

As  far as adjusting manual slacks in the rear, I drive the bus on 2 rough cut 2" boards, and slide underneath on a low profile creeper. The passenger side one is more difficult to reach because the diff is offset to that side, but is doable, (I am skinny). With manuals, I go in there a couple times a year to adjust them, then I know what's going on. You tend to ignore automatics.

My broken control arm on that slack brings the question: why did it brake in the first place? I was busy today dealing with the infamous drum to hub screws on the front axle. Tomorrow, I will take the broken slack adj. off, and see if the S cam shaft is binding, or what is the matter...

JC

[Gary W]

JC I had a stopping incident this summer, when  I took the bus into the shop they found 3 auto slack adjusters were broken and way out of adjustment. I had them replaced along with the front drums and shoes, they were pretty rusty. Now I have great brakes.

Gary

[bevans6]

I personally think the biggest problem with auto slack adjusters on our buses is lack of use and lack of maintenance.  I will probably drive my bus for five years before the brakes wear enough to make the slack adjuster actually adjust.  Will it adjust then?  How the heck would I know.  All I can do is measure the pushrod extension once a year or so.  Are manual slack adjusters better?   Who can tell?  I know that manual slack adjuster are a lot more expensive than automatic ones.  The joys of sticking with out-moded and archaic technology.

Brian

[lostagain]

Gary, and everyone, what is remarkable is that last time I checked last winter, everything was good. I only drove 12 or 15000 km this year. I don't use the brakes much as I have good Jakes. And now this. It reinforces my belief that periodic inspections are a must, more often than not. That is why commercial vehicles have to have inspections every 6 months in BC, more often in other places. You can't keep on driving assuming everything is good, you have to look under there!

JC

[wg4t50]

My setup uses the disk brakes with the auto slack adjusters, I never trust the auto part, also have the Allison 4000R with the retarder, very effective so the wear on the disk pads is very little, with 112,000 miles on the unit, the pads & rotors still look new.  Check the slack adjustment every  6 months.  After the MC7 brakes, this stops like a car.
Dave M

[Jon]

Once a year??

I am not a certified mechanic and I did not sleep in a Holday Inn last night, but I still continue to be amazed at the lack of respect most conversion owners have for their brakes. I realize I am going to get flamed for saying this, but here it is. First, every single driver should do a brake check daily. If you don't know how to do a standard DOT brake check you shouldn't be driving the bus.

Second, checking the mechanical brakes is easy if you can see the end of the arm on the slack adjuster. I cannot recite the travel distances for each size brake. but simply stated if the travel on the brake chamber push rod is so great the red ring on the push rod is visible the brakes are in dire need of adjustment. No skills needed. Just look at the rod while someone steps on the brake. At the same time you can observe the slack adjuster function. If something is broken or out of whack it is going to be visible if you have even the slightest understanding of what you see. On my smaller sized brakes I think if the slack adjuster traveled 5/8" total it was OK. On the bigger ones it was about 1" of travel. Somewhere there is a list of travel distances. Maybe someone can link to them.

If you need to pay a mechanic once a year to look at something you should understand and be doing I think you should step back and reconsider if you are really safe and if you should be concerned.

Fire away. I can take it.

[Oonrahnjay]

... I realize I am going to get flamed for saying this, but here it is. First, every single driver should do a brake check daily. If you don't know how to do a standard DOT brake check you shouldn't be driving the bus. ...

     No fire from here.  I had to rebuild my entire brake system (I have/had original compressor, foot brake valve, and brake drums and very little else).  First thing I did was download the table of contents on Bendix's tech data page and downloaded and read everything applicable.  When I installed the new brake cans, I hired a pro to crawl under the bus with me and teach me everything I should know (grease nipples, rod lengths, angle of adjusters, etc.).  I can tell you where my quick release valve is for my front brakes because I bolted it on and I know the part number for it because I bought it and recorded the number (also the "crack pressure" number). 
     And as part of this, I took $300 out of my pocket and bought myself Bendix Brake School.  No sirree, you won't get any fire from this direction.

[lostagain]

Jon, I agree totally. I have come to know you through these bus boards as a very thorough mechanic who is fussy about all systems being in perfect condition.

In my case, I do all my own maintenance. I take the wheels off every winter and service everything, clean, grease, correct as needed. I crawl under several times a season to check slack adjusters, grease again, etc. In this particular case, I did not notice anything was wrong, and I don't think anybody else would have. The adjuster was pushing the shoes to almost contact the drum, so I didn't notice they were off by visual inspection. The parking brake was holding the bus adequately by the other wheel. Nothing was showing up wrong in the pre-trip inspection. I only check the travel on the auto adjusters at the back once in the winter, because (wrongly obviously), I assume that they will do their job without babying in the summer. Once I replace them with manuals, I will check them more often, like I do with the front manuals. The only thing I noticed was, as noted in my first post, the opposing wheel locking up once in the rain. That sent me under the bus that night to look, and didn't see anything bad. The braking performance has never been great on  my bus, but it felt normal to me for a bus. I have driven lots of them in my life. The part of the slack adjuster that broke is the very end of the control arm at the 90* where it bolts to the bracket. I did not see that until I started scraping dirt and grease off with a screwdriver after I removed the wheels. The break looks really fresh. Maybe it happened more recently than I first thought.

This only makes me more diligent in maintaining my bus, and other equipment, in the future. And I hope that others reading this will also realize the importance of good maintenance, for everyone's safety.

JC

[Gary W]

I have a certified mechanic check the brakes once a year or more often if I notice a problem.

Gary

[Jon]

I like what oohnahnjay said. I too have taken the 3 day Bendix class and it is something I would highly recommend. Having a mechanic under the coach with you is another piece of excellent advice.

Our brakes suck. They stink. We cannot stop worth a damn. That's because even when everything is working perfect our stopping distances compared to the average car are 2 1/2 to 3 times the distance. So we are in deep doo-doo when something is wrong. Please all be safe.

[luvrbus]

There are so many different automatic slack adjusters models and sizes on the market why are the Haldex/Midland preferred over the Bendix anyone have answers ?
I have been to several Bendix classes over the years the Haldex or Wabco classes are far superior class IMO and cheaper 50 bucks vs 300 anyone can afford 50 bucks and I hear that Haldex has a online version for training no excuses for not knowing  

[Oonrahnjay]

... I have been to several Bendix classes over the years the Haldex or Wabco classes are far superior class IMO and cheaper 50 bucks vs 300 anyone can afford 50 bucks and I hear that Haldex has a online version for training no excuses for not knowing  

     One thing I will say for the Bendix class and our buses, there is a lot of time given to the theory, mechanics, and troubleshooting-by-electronics of the ABS and stability systems.  It's great and all but how many of us have electronic brake and brake/suspension systems?  I would have much preferred to have paid for 4 days and knocked the last day off but the full program was incredibly valuable.  (I've never taken the Haldex or Wabco classes so I can't compare them.)

[luvrbus]

Last Bendix class I went to the instructor would not even mention the DD3 braking system, I didn't let die though and he was getting a little agitated with me