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
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
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
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
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
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
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
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.
Quote from: Jon on November 13, 2014, 04:25:43 AM... 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.
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
I have a certified mechanic check the brakes once a year or more often if I notice a problem.
Gary
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.
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
Quote from: luvrbus on November 13, 2014, 11:07:39 AM... 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.)
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 ;D
My last two buses had ABS, but as a homebuilder knows the available coaches are not all going to be 50 year old GMs so that ABS knowledge is valuable.
Truth be known an ABS system is the epitome of simplicity and nothing to be afraid of. If a sensor detects a wheel is slowing faster than the others it tells the "brain" and the "brain" responds by activating the ABS valve. All that valve does is block air flow to the brake chamber from the braking system relay valve, and open the side that has air pressure in the brake chamber, essentially releasing the brake until the speed of the wheel matches the others. When the speeds are the same the system goes back to normal.
Obviously there is pulsing until all the wheels are in concert.
I have ABS on my tag axle only and I hate it. It hasn't worked since the day I got the bus and the ABS bulb long ago burned out from being on all the time. I tested the sensors with an ohm meter and they seem to show the right ohms. I think the electronic box is dead and the box is long obsolete. The best Bendix or anyone can tell me is to replace it with a box for a trailer. I just live without ABS on the tag axle because all it does is stop premature locking up of the tag axle brakes.
I took the Bendix class, and while it is good, it was not really what I hoped for. I was hoping for a little less theory and more practicality. They really didn't talk much at all about the wheel end stuff which has been all of my problems. A local tech college has a diesel mechanic program and I've tried to see if they would let me in just the air brake class, but the air brake class apparently is only offered once every two years.
So, like some cars, does a bus ABS system increase your stoping distance by up to 60%? I realize it has benefits in skid control but I've found it's really not at all helpful when you really want or need to STOP.
Having lived in the western NY snow belt in a previous life I spent a lot of time driving on snow and ice covered roads. At the time the rule that was often stated was in a panic stop hit the brakes hard and do not lift your foot. When you do that you hear and feel the ABS pulsing. Every time you get that pulsing the ABS system is alternately applying and releasing the brakes.
If you are sensitive to what your vehicle is doing you can modulate brake pressure to apply stopping force with brake application without the ABS engaging. My gut tells me anytime the ABS is actively regulating the application of brakes, it is also releasing the brakes so there is likely to be some loss of performance compared to the stopping distances a skilled professional driver can do. My gut therefore also tells me that as a non-professional that does not go out every day and practice maximum braking performance under adverse conditions that the ABS is going to do a better job than I can do. Its real advantage is in assuring the driver the braking is controlled which means steering functions will still work and the vehicle is less likely to start sliding in a circle.
I got the slack adjuster off last night. Everything else downstream from it (S cam shaft, cams, rollers, etc) is in good condition, and moves freely. It is a Haldex P/N 41910768. I can't even find that one on their site, let alone a manual equivalent. It has a 1 1/4" offset, 10 spline, 1 1/2" diameter spline, 7" arm length, 1/2" pin hole. Not very common. I'll be in Calgary this afternoon, and will look in the Fort Gary Industries store. They have lots there, but mostly for trucks. I have to dig out the receipt for the manuals I got a couple of years ago for the front. I think Inland Kenworth got them for me.
JC
Check the Euclid site or call Jefferson in OKC same adjuster as on a Eagle,Ed will have the manual or auto adjust if your source fails
Thanks Clifford,
the control arm pivot is very stiff. The Oring is bulging out. The guts are full of moisture, even though it would still take grease. I have to think that is why it broke. Am replacing both sides on the rear.
JC
Quote from: jetart on November 13, 2014, 06:26:44 PM
So, like some cars, does a bus ABS system increase your stoping distance by up to 60%? I realize it has benefits in skid control but I've found it's really not at all helpful when you really want or need to STOP.
I've never noticed the ABS on my current car activate on a panic stop on dry pavement. We are getting off the original topic here.
My bus ABS has never worked and it was only for the tag axle anyhow. I would probably make it a priority to get fixed if it was for all of the brakes. We drove through a snowstorm in 2009 where any application of the service brakes resulted in sliding and ABS would have been nice. We used the Jake brake because the bus didn't slide when we used that. We drove at 20 to 25 MPH for a good five hours that time. We would have stopped, but we would have been stuck there for several days. We eventually drove out of the storm.
Don't want to tell anyone how to drive, but I have never seen any owner's manual on any truck or bus that does not specifically warn against the use of a Jake or retarder in slippery conditions.