How can you tell if air brakes are in need of service?

[steined]

I have an offer in on a 2000 vintage Monaco Dynasty with high mileage, how can you tell if the brakes need servicing?

My experience with Class A coaches is limited to two 10 mile drives. I had driven a 2000 Diplomat (didn't buy it) with what seemed like extremely touchy brakes. The Dynasty I have an offer on had what I would call more of a wooden feel to the brakes. However I was on a rural 4 lane and had a light change on me and it did stop VERY well then. The feel between the two coaches was quite different. Just not sure what is normal. Extremely touchy, or wooden with deliberate pressure required in the initial travel.

Thanks in advance!

[B Bob]

When I test drove about a dozen DP coaches 5 1/2 years ago they all had different "feels" to their brakes. One of the Beavers I drove (owned by Monaco) had "wooden" brakes too. Scared me a little. The coach I bought seems about right. The answer on getting brakes checked though is any full service RV place. Our coach has 123,000 miles on it and the brakes have never been replaced and don't need it. They work well.

[theroc]

steined, one of the reasons I'm an advocate for all owners of diesel pushers being tested for the special non-commercial driver licenses is that I believe in most states that do require a non-commercial Class B or whatever class license the specfic state requires, is that most also require the applicant to pass the air brake endorsement tests. I believe that all diesel pusher owners have a rudimentary understanding and be able to demonstrate elementary knowledge of an air brake system.

I've posted the attached video previously but it's worth posting again. It's an instructional video for transit drivers at King County Metro in Seattle in preparation for the CDL test. Diesel pusher owners in Washington state do not require a non-commercial license but in those states that do, as mentioned, most require an air brake endorsement also. I was once a commercial bus driver and I feel that the KCM video makes good viewing for any diesel pusher owner whether their state requires a special license or not for as I say, it's good for any pusher owner to understand the basics of air brakes. Most do but many do not.

Much of the video you can skip but the brake sections are scattered throughout. Since a transit bus is similar to most pusher mothorhomes, the descriptions and tests in the video will be relatively close to what you have or can apply on your own coach.

Braking and air system demonstrations:

3:03 to 5:13 ...includes air leak test, low air warning devices, parking brake protection valve, and air governor cut-out.

12:52 to 14:10 ...front brake components, slack adjusters, etc.

16:24 to 17:44 ...rear brake components, etc.

Again, this is just an elementary instructional video that shows what must be demonstrated on the CDL exam or in some states, if you are taking the non-commercial test with air brake endorsement. You may know some of what is being shown already but in case you don't, it's still a good primer for new diesel pusher owners whether they are in a state that requires a test or not ...it's just good common knowledge that every pusher driver should have.

I know it doesn't answer your question on "wooden feel" on the pedal. My experience in both driving a bus and in my motorhome is strictly subjective and from the seat of the pants but I know the brakes are slack when I "feel" nervous about not being able to stop in time. In my early days of driving buses back in the 1970s, I drove many buses that I immediately called in and refused to drive further because of slack brakes. However, nowadays, transit buses very rarely are put out on the road with slack brakes. My experience with newer buses and in my motorhome is that if the brake systems are checked, maintained, and adjusted regularly, very seldom will you have slack brakes ...or that feeling of being on the verge pooping your pants because you almost didn't stop in time before hitting the car in front of you, etc.

Personally, every once in awhile, I'll secure everything in the motorhome and in an empty parking lot, make several "emergency stops" to get a feel of how the brakes are performing. You may not have the opportunity (or let's hope not) to do several hard braking maneuvers out on the road in reality so I do this intentionally every so often in a controlled environment so that I can get a subjective feel for the braking ability of the coach. It's no tapley test (most transit agencies do use a Tapley in addition to other tests to determine braking ability of the coach) but it still gives me an idea on how the brakes are performing.

https://www.youtube.com/watch?v=eYTvdGUkNac

ETA: Hah, my apologies. I re-read your post and all of what I just posted may not be of any interest to you as you have not yet actually purchased the coach, correct? So forget for now all that I posted until you actually need it if you need it at all. What I would suggest is that you have the brakes inspected by a credible mechanic before purchasing the coach. You shouldn't really determine if the brakes are good solely on a short test drive. As others have said, each coach will have a different "feel" to the pedal ...some have more travel distance than others, different engagement points, etc. ...also, a treadle brake will have a different feel than what some of the "regular" suspended pedals that some Monacos and many higher-end coaches have as they are sometimes physically adjustable.

[steined]

Thanks theroc.

I was already reading an article (From Canada) on air brakes, theory, test, etc. Depending on what my state offers, I'll likely get the endorsement if for no other reason than to learn more.

What you describe as slack brakes, may well be what I was feeling. I'm going to have them check it out at a chassis shop prior to purchase. I just didn't want someone to say "That's normal" in the shop when maybe it isn't. I'm a newbie to air brakes.

Thanks

[FormerBoater]

Many DP owner/operators are not familiar with the need to calibrate their automatic slack adjustors.

If the slacks have not been calibrated, the air brakes cannot be fully engaged.

The procedure should be part of the owners regular routine.

There are many videos on the web on how to calibrate your slacks, but basically it is six consecutive full stroking of the brakes for 30 seconds each. If yo roll your window down you can hear the slacks make a clicking noise as they adjust.

Good idea to conduct this procedure before you pull out for your test drives.

[twinboat]

Former Boater,

Can't find any videos or calibrating slacks. Maybe some brands do, but that would only apply, after a repair.

Automatic adjusters are self adjusting, why would they come out of adjustment, sitting around.

To the OP,

The way to check. air, drum brakes, is to look at the shoe thickness, thru the inspection plate. With that you need to know how thin is bad.

You can check the adjustment by observing the movement of the brake chamber rod, where it hooks to the slack adjuster.

More then 1 inch of travel, means they need adjustment. Since they are self adjusting, and shouldn't be out of adjustment, they need fixing.

Forcing them to adjust, just send the problem down the road, with you in It.

[Gary RVRoamer]

You want a truck chassis shop, not an RV dealer, to check or repair air brakes. A few large RV stores have qualified chassis departments, but most are not experts or even knowledgeable amateurs on chassis problems.

Auto slack adjusters work best with hard braking, and motorhomes generally don't get much of that, so the general suggestion is to brake sharply now and then, both in forward and reverse, just to give them a chance to do their thing.

Air brakes have a slight lag between pedal and braking - could that be the "wooden" feeling? Was the air pressure up in the tanks, i.e. dash air gauges showing about 125 psi? The brakes work all the way down to around 65 psi, but reduced air pressure would change the feel. Normal operation of the air system is right around 125 psi. Anything less for more than a few moments indicates a significant air leak or a compressor problem.

Other than that, you tell if the brakes are working by how well the coach stops, straight and steady. It is rare for a motorhome to need new brake pads or anything like that - the brake system is made for much greater wear & abuse than most any motorhome ever sees.

[deandec]

Here is a quote from HDT trucking info that might be helpful in understanding automatic slack adjuster adjustment on a 5,000 mile per year DP.


“But in my experience, the primary cause of auto slacks stroking beyond their limit, is – believe it or not – good drivers,” he says. “I’m talking about the driver who never makes an application harder than 15 or 20 psi because he or she never has to. They’re the ones who manage speed well, keep a safe distance, and coast up to traffic lights. These drivers hardly ever put enough torque through the adjuster to cause the ratchet to roll over to the next peg. Consequently, as the brakes wear naturally, the auto slacks aren’t compensating. What these drivers need to do is make half a dozen full pressure applications once a week or so to get the adjuster to turn over, and then visually check the stroke before leaving the yard. ”


Part of the DOT Pretrip Airbrake test is slowly pumping down the air system with the parking brake released. That step should perform the adjusting of the automatic slack adjusters described in the paragraph above.

You can find lots of versions of the pretrip air brake test on the Web.

[FormerBoater]

Originally Posted by twinboat

Former Boater,

Can't find any videos or calibrating slacks. Maybe some brands do, but that would only apply, after a repair.

Automatic adjusters are self adjusting, why would they come out of adjustment, sitting around.

To the OP,

The way to check. air, drum brakes, is to look at the shoe thickness, thru the inspection plate. With that you need to know how thin is bad.

You can check the adjustment by observing the movement of the brake chamber rod, where it hooks to the slack adjuster.

More then 1 inch of travel, means they need adjustment. Since they are self adjusting, and shouldn't be out of adjustment, they need fixing.

Forcing them to adjust, just send the problem down the road, with you in It.

Calibrate/make sure they are in adjustment....whatever you want to call it.

The point is that Automatic Slack Adjusters, which virtually all DP have will need to be calibrated regularly. They get out of adjustment via use!

This guide calls for fully stroking the brakes 10 times. Others call for a minimum of six as I recall.

Don't do this and the day may arrive where your rig cannot stop in the distance that you want it to!

http://www.idealease-abetterway.com/...04_22_2011.pdf

[steined]

Thanks everyone. This has been very informative! I now know how air brakes work in more detail (thanks to some of the links) than I ever thought possible! Very cool stuff!

[ahicks]

Could not possible agree more with Gary's advice above. Do not take or send a DP to an RV dealer for ANY kind of chassis inspection/service. I wouldn't let one change my oil. 99.999% of them are clueless when it comes to DP chassis, no matter what they tell you.

You're looking for a place capable of, and used to working on, medium duty trucks (like a larger UPS or dump truck).

I would not buy a DP that has not had an inspection done by a shop that knew what they were doing. MANY components (e.g. radiators, air bags, etc.) that are exclusive to these larger vehicles need to be given a good once over. It's a couple hundred bucks that will let you sleep much better... or save you from a several thousand dollar mistake.

[guardrail53]

Originally Posted by deandec

Here is a quote from HDT trucking info that might be helpful in understanding automatic slack adjuster adjustment on a 5,000 mile per year DP.


“But in my experience, the primary cause of auto slacks stroking beyond their limit, is – believe it or not – good drivers,” he says. “I’m talking about the driver who never makes an application harder than 15 or 20 psi because he or she never has to. They’re the ones who manage speed well, keep a safe distance, and coast up to traffic lights. These drivers hardly ever put enough torque through the adjuster to cause the ratchet to roll over to the next peg. Consequently, as the brakes wear naturally, the auto slacks aren’t compensating. What these drivers need to do is make half a dozen full pressure applications once a week or so to get the adjuster to turn over, and then visually check the stroke before leaving the yard. ”


Part of the DOT Pretrip Airbrake test is slowly pumping down the air system with the parking brake released. That step should perform the adjusting of the automatic slack adjusters described in the paragraph above.

You can find lots of versions of the pretrip air brake test on the Web.

X-2, Very good info! Rail!

[Ray,IN]

Originally Posted by FormerBoater

Many DP owner/operators are not familiar with the need to calibrate their automatic slack adjustors.

If the slacks have not been calibrated, the air brakes cannot be fully engaged.

The procedure should be part of the owners regular routine.

There are many videos on the web on how to calibrate your slacks, but basically it is six consecutive full stroking of the brakes for 30 seconds each. If yo roll your window down you can hear the slacks make a clicking noise as they adjust.

Good idea to conduct this procedure before you pull out for your test drives.

Spartan says it takes a minimum of 100# pressure to activate the slack adjusters. This does not usually happen during normal driving circumstances. It requires exactly what you describe.
Depending on the type of brakes, S-cam, or wedge, there are 2 or 3 zerk fittings at each wheel that must be greased per mfgrs. maintenance, or the slack adjusters may not adjust properly. and/or the brakes may not move as designed.
The first time I ran the sequence, my LF brake popped loudly each time. This was after I had greased all the zerk fittings on the chassis. Now it works as designed and doesn't make a sound.
For background, I had just bought this MH, after it had sat parked in a barn for 6 years.

[DMTTRANSPORT]

Auto slack adjusters require manual adjustment twice a year depending on miles.