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.

[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

[Mark3101]

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