Sticking brake

[flloyd]

Since I've owned my coach (since last summer), I've had a problem with the brake lights staying on for several seconds after I release the brake pedal. On the advice of several, I replaced the two brake light air switches, to no avail. The lights still stay on after the pedal is released.

Last summer, I also noticed that after I would park and exit the coach, that I would often hear a squeak from the undercarriage, which sounded like the coach was moving a bit, but it wasn't.

I'm on a trip now from Arizona to Florida and it's much colder outside. Now, after having replaced the brake light switches, I finally noticed (while driving) that when the squeak is heard, the brake light indicator goes out. This indicates to me that there was pressure still on the brake and that it wasn't being released quickly enough.

During this trip, there were a few instances where the light stayed on for a half mile or so. Nothing felt different otherwise, however the light was annoying and it prevented the re-engagement of the cruise control. Last evening, upon stopping for the night, I looked in horror as the right rear drive wheel rim was filled with brake dust. By golly, I think I've found it!

I spoke with Doug today (from Excalibur) and have made an appointment to see him since I'll soon be in his neighborhood. He says that it might be a Relay valve, or perhaps the Treadle Valve. I just hope that I haven't toasted the shoes too badly, or perhaps even a drum.

The good news is that today I found that by stabbing the pedal quickly, the brake will often release at once. Now that I'm attuned to the sound and the feel, I can clearly feel both the resistance of the stuck shoe as well as the release squeak.

Today's drive was about 350 miles, all interstate with very little brake usage. No additional brake dust. Fortunately, I think that I've caught this one and have a work-around, but still remain anxious as to how bad the damage is.

Has anybody else had this problem?

[Jon Wehrenberg]

Fred,

I am not sure the two issues are related. The brake light switch is a pressure switch, and if air pressure to the brakes is applied it closes and the brake lights come on. If for some reason the pressure was not being released it is unlikely a single wheel would exhibit signs of brake drag caused by this condition. I think all brakes would drag. While I agree the brake treadle or the relay valve could be the culprit both brakes on an axle or all brakes on a circuit would be dragging.

To help with the analysis, if you have an infrared temperature gun drive a distance and check the temps at each wheel. If the temps are uniform then it suggests all brakes are on or all are off. If only one shows evidence of dragging then I would focus on brake adjustment.

Your brake pedal doesn't actually apply your brakes. It sends an air signal to the relay valves which introduce air into your brake chambers proportional to how hard you step on the pedal. As soon as you release the brake pedal you likely hear the escaping of air, that being from a quick release valve at each axle which I think is combined with the relay valve in our coaches. If one of those is not functioning properly (releasing air) that might contribute to the problem. When you take your foot off the foot pedal it might not close off the air to the quick release valve. But again, if this were the case an axle or all wheels would show excessive brake dust. and would show high temperatures.

If you can find a truck stop with an open pit see if they will allow you to go over it and take a look at each brake. When you apply the brakes you will see the brake chamber push rod move every slack adjuster arm. Our coaches are twins underneath so the arm ovement you should see will be in the 1" range. That would be the correct travel if the slack adjusters are working correctly. Upon releasing the pedal you should see the slack adjuster arm fully retract from the applied position. Do this with the emergency brake off. The opportunity to get beneath the coach and watch your brake operation will be worth its weight in gold.

At each axle when the brakes are released up in the center mounted high above the axle will be the relay valves. Each one should give a loud sound of escaping air when the brakes release. Listen at each one. That noise will be accompanied by the slack adjuster arms retracting. If one of the arms does not return or apply the same distance as the others, and especially its counterpart on the same axle you can zero in on that to see what's going on. It could be bad adjustment, a weak or broken return spring in the brake chamber, a bad quick release valve (relay valve) or air from the prake pedal still being applied, but that will affect more than one brake.

You won't need more than 15 minutes over the pit to see all of the above and it will give you information that will help in the analysis.

[Jon Wehrenberg]

Forgot to mention the possible damage from a dragging brake.

The obvious is excessive wear on the shoes, pads, drums or discs. The heat generated if excessive could harm the oil in the hubs and differential which in turn could affect the bearings. I would certainly take a lot of time looking over the drums and discs looking for cracks or warping.

[travelite]

The only thing I would add to Jon's description is that a dragging brake can transfer a lot of heat into a tire. The tire can blow out or even catch fire. Also, when you finally do isolate the problem, do repairs in pairs. In other words, what you do to the left side, do to the right side. Air brakes work by sending pressure waves, brakes work better if propogation delays are the same from side to side.

[Pete]

Fred, I had a similar problem on my previous coach. I had to have the Emergency brake valve replaced (by Prevost Ft Worth) during a trip to Colorado. Shortly after departing Prevost, I noticed that the Cruise Control would not work, additionally, trucks behind me called me on the CB radio that my brake lights were on! . I called Prevost, and relayed the problem to them....they in turn made arrangements for me to go to a commercial bus company in Denver....To make a long story short, it was a faulty Emergency Brake valve. It was replaced and all was well. Cruise Control worked and the brake lights were off. So you might want to have them check/replace the valve. Also, if your travels bring you through Sealy Texas, (50 miles west of Houston) you are welcome to overnight with us. 50A, and Water. 979-627-7050.

[joelselman]

I have the brake light delay problem on my coach. I'll be watching in anticipation of a resolution.

[Mark3101]

A very easy fix could be if the pedal is simply hanging up a bit. We used to see this in trucks quite a bit, especially if they had been sitting around for a few weeks. Apply the brakes and then see if the pedal returns all the way back. Give it a pull to check it. That could be the issue...

[rahangman]

" I called Prevost, and relayed the problem to them....they in turn made arrangements for me to go to a commercial bus company in Denver....To make a long story short, it was a faulty Emergency Brake valve. It was replaced and all was well."

Pete, we are often in Denver area, could you pass along the name of the Commercial Bus company that you used? It is always good to have a "Go To" location. Thanks

[GDeen]

Add me to the list. I had Prevost FW check it a year ago and they focused on the air relay in the front lower drive side compartment. Ultimately they said it "might" cure the problem by replacing, but lots of labor due to all the air lines. I passed with notion of doing it myself. Turns out, after leaving, the problem was gone I assumed due to the multiple hard cycles they put the system through while trouble shooting. On a Christmas trip to OK last December, I noticed the problem is back and I have it on my list.

One of my favorite CB moments ..."get that pretty ass bus out of the hammer lane if you are going to ride the brakes." .... as I pulled away from him...

Count me as watching also.

(PS - Fred (Floyd), great to see you back around!)

[Pete]

I gave all of my records to the people who bought my old bus, but if my memory serves me right it was Arrow Stage Lines. I did a search, and it came up. They are in the Aurora area, but the actual address is in Denver. They seemed to be very knowledgeable. Hope this helps.

[dreamchasers]

I have researched information to educate me on how the Bendix air brake systems work on our coaches and the attached document is the most comprehensive i have found. The document explains all the components of our brake system and how they interact.

I had a brake air leak that resulted in the loss of brake air overnight. Using this document to understand the function of the modules helped be find and replace the leaking module. The SR-1, page 25, was the device that was leaking causing the lose of brake air. The brake air was continuously venting out of the bottom port. It is activated each time the parking brake is applied. I replaced it.

Click below to download the .pdf for Bendix information.

http://www.texasdrifters.net/pog/Bendix Brake Information.pdf

Hector

[Mark3101]

Fred: Did you get this resolved, and what was it? Inquiring minds want to know.

[AmeriStar]

I gave all of my records to the people who bought my old bus, but if my memory serves me right it was Arrow Stage Lines. I did a search, and it came up. They are in the Aurora area, but the actual address is in Denver. They seemed to be very knowledgeable. Hope this helps.

Arrow in Denver happens to be one of Americas foremost best bus shops in the country. Gene (their maint supervisor) is recogised by our industry as one of the best. We often will 'pick his brain' on issues we have a problem with.

[JIM CHALOUPKA]

Come on Fred, you started something and people are waiting to help and at least know if your OK.

What is your status! Don't be offended but ge wiz, you might as well not started this.


JIM :)

[flloyd]

Headed to the shop today, after several days at rest. We moved the coach a short distance (20 miles) the other day and while the brake light still sticks, it goes out now in 10 to 15 seconds like it did last summer. Whatever the problem, it seems that it's worse in cold weather. I'll keep everyone posted with a full report once once we have more details.

[GDeen]

Headed to the shop today, after several days at rest. We moved the coach a short distance (20 miles) the other day and while the brake light still sticks, it goes out now in 10 to 15 seconds like it did last summer. Whatever the problem, it seems that it's worse in cold weather. I'll keep everyone posted with a full report once once we have more details.

Ditto mine.....

[Jon Wehrenberg]

I hope for your sake that the warm FL temps do not make the problem go away because chasing an intermittent problem or one associated with temps or conditions you cannot duplicate tends to drive you to the poor house and you still have no assurance the problem is gone until it gets cold again.

[flloyd]

Last week I completed a 3-day stay at Excalibur Coach's repair facility, one of our POG sponsors.

Here's what happened, and what I learned:

The "Brake Dust" problem on my p/s drive wheel wasn't brake dust at all. It was powder from the insulation panel that had fallen from above and had been dragging on the tire for about 1000 miles. The insulation panel is made of about 1.5" of fiberglass with a hard outer shell of plastic. These line the top of the rear wheel wells. Since a good portion of this panel was now gone (to dust), we elected to replace the panel with some modern insulation board (about 1/2" thick), plus some foam. (see pictures)

The sticking brake was a bit more tricky but I am confident that we solved the problem. Upon arrival to Doug's shop, I was able to demonstrate the problem easily. Upon removing my foot from the brake pedal, the light would stay on. About 10 seconds later, we would hear a squeak (from under the front end) and then the light would go off.

Doug suspected the master brake valve and had one of his technicians attach a pressure gauge to one of its outputs, to see if in fact pressure did remain in the system after removing foot from the brake pedal. They saw the phenomenon only once and after over an hour of testing, re-pressurizing the main system, etc., the problem did not repeat. We went ahead and ordered the brake valve which would arrive the next day. Doug explained that since my coach was built, the valve has undergone a number of revisions and the new valve didn't look exactly like the old one. One major difference is that it had a much larger exit orifice, where the control air goes when the brakes are released.

The new master valve was installed and along the way we discovered several other leaks in the compartment, and ended up replacing two Norgren valves. One 5-way and 1 3-way valve that was controlling the front air bags. I had no idea that my air system needed such maintenance but it was somewhat like a frog being boiled in water. You tend not to notice change that takes place over time. One thing that was very surprising was a 90-degree brass fitting that was cracked along its side from over-tightening. It was in the Aux system.

After replacing the parts, the system now holds air much longer. Whereas the Aux system would previously run down in 20 minutes or so, it now goes for at least an hour between compressor runs. I know it's not perfect, but I'm satisfied for now.

The new brake valve is quite remarkable. The brakes have a whole new feel, which I liken to the difference between standard and power brakes on a car. Now, just a touch gives great braking power, much more than before. The "sticking" problem is completely resolved, and we drove the coach about 100 miles through a lot of city traffic with no issues at all.

One item that remains unfinished (we didn't work on it) is my tag axle lift. I've written about it here before so to summarize, when I lift the tag it seems to take forever to drop back down. This usually happens when I'm maneuvering to park and so the coach will be parked ass-low for quite some time, usually until I leave the location. Occasionally, the rear end will creak and squeak as it tries to re-lift, but nothing seems to work until I get the engine started again and get some serious air back there. Then it will be fine for until I lift the tag again.

It is pretty clear now that my tag problem is most likely Norgren valve related and that until I get another handful of them replaced, I'll just not be using the tag lift.

Below are some pictures for your consideration.

https://lh3.googleusercontent.com/_QkzN2-KPKAg/TWE5pZsoRtI/AAAAAAAACEw/dB6Mn7adVuc/IMG_4305.JPG
Old Brake Valve

https://lh3.googleusercontent.com/_QkzN2-KPKAg/TWE5rcZAhUI/AAAAAAAACE4/4bem4L_Y39g/IMG_4314.JPG
Remnants of Wheel Well Insulation

https://lh6.googleusercontent.com/_QkzN2-KPKAg/TWE5s55x8zI/AAAAAAAACFA/gv0j4JmpR5g/IMG_4319.JPG
Wheel well repair (before painting)

[Jon Wehrenberg]

Great report, Fred.

As to using the tag axle lift, drop your front bumper and look up at where the steering arm comes through the floor. In that area should be a "cam" and a microswitch with a lever arm. When the steering is turned full lock in either direction the "cam" which is more like a stainless steel frame activates the the switch lever. When that happens your 3 port Norgren valve, which you are contemplating replacing is actuated. It closes the path between the 2 drive axle air bags and exhausts air from the tag axle air bags. This doesn't lift your tag axle, but it takes about 7000 or 8000 pounds from the tag axle tires automatically.

I NEVER lift my tag axle unless the turning situation is so extreme I want every fraction of an inch available to me. The automatic feature is more than enough assistance on sharp turns.

I suspect the delay in dropping the tag is due to another valve, located on the frame above or behind the three port Norgran that might not be shifting when it get the pilot command, thus releasing air in the brake chamber that lifts the tag. It sounds like the tag air bag is inflating, but is being fought by the air in the lifting chamber not released through that valve.