Air valve sticks open

[tmitchell]

About 10,000 miles ago, after leaving a CG, I could hear a shrill steady whistling noise, caused by escaping air. It lasted about 1/2 an hour. Yesterday about an hour after leaving a CG and after stopping to pay a toll, the whistling sound started again. This time it lasted for over an hour. I would tap the brakes and it would go away for a short time, less then a minute. Occasionally it would stop on its own, but would restart again.
When I got home it wasn't making the noise, so I couldn't go under the MH to locate the source.
I know there are 3 air valves for the air tanks. Does anyone know which would be the most suspect?
I kept an eye on the gauges and never lost air pressure.
Are the air valves cleanable, or do you just replace them?
Tom

[deandec]

I had the problem a few months ago when I could not build air pressure. Dismounted and found the front valve hissing.

Because it wires on it, I hit it with a wrench in frustration. It has worked fine ever since but I still carry the wrench with me.

[Roadking]

The saftey of you, your passengers, and everyone on the road depends on your air brakes and air systems working properly. IF you have air brakes, then these systems must be fully operational and well maintained. NON-LEAKING Air systems are a key saftey item. If you drive a rig with air brakes you should know the basic test proceedures to determine if the compressor is pumping to minimum specs, if leaks exceed minimum leak specs, and basic tests to determine if you your brakes even work. These tests should be done once each day PRIOR TO MOVING the vehicle. If you don't know how to perform these basic tests then you should not be driving a vehicle with air brakes. Do some simple research. One potential area to learn is to Get a copy of your states air-brake certification test for commercial drivers and read it. You may learn something even if you are an expert. You should be familiar with the basic saftey tests to determine if your brakes are operational and safe.

If your rig has a problem with leaking air where pressure can not be built, or held, or if there are clearly auidible leaks then these problems should be corrected prior to moving your rig. They should not be fixed by pounding on valves or ignoring them. Sorry for ranting, but this is common sense and saftey for everyone.

[gripper]

OK Roadking, you have now scared me sufficiently. I have never made these air brake tests, in the 2 years that I have owned my Fleetwood. Can this "test" information be downloaded from the internet or where can I find it?

Roland (gripper)

[Roadking]

I'm no expert here, only passing on what I remember from reading in the past. I downloaded the South dakota CDL air brake certification study guide from the South Dakota DMV site. As I recall the South Dakota guide describes a series of tests which I believe some, or maybe all, would apply to any air brake system.

The guide describes a series of tests and visual examinations that are to be performed and a recommended frequency for performing the tests.. i.e. daily, weekly, ect. I don't recall the details but the tests included things like: 1) pressing the treddle several times and monitoring how much the primary and secondary pressures drop 2) relieving air pressure to a point where the "low air" alarm is triggered and monitoring that pressure and ensuring the alarm is activated by at least 80 psi. , 3) determining how long it takes the compressor to pump up to operational pressure 4) determining if there are any leaks and how significant the leaks are i.e. how much pressure is lost over a period of time 5) determining if service brakes work prior to moving the vehicle, 5) determining if emergency brakes work, 6) examing slacker adjusters to determine if they are properly adjusted 7) determining if auto adjusters are working properly, examing brake pads to determine if they are within wear limits, and others... THis is from memory and I'm certainly no expert so I I don't have the details.

I would guess most state DMV sites would have manuals to assist taking the Air brake certification test. Every time I read the manual, which I need to do again, I learn, or in the case of my CRS (Can't remember [moderator edit]), relearn, something.

[tmitchell]

Thanks for the replies.
I screwed together some 2x8s to drive the front wheels up on so I will have enough room to slide under the MH, with the air discharged.

I am going to pull the lanyards to expel all the air from the tanks, then change the air drier filter.

Hopefully the air noise will happen when I restart the engine and the air tanks fill. Then I should be able to tell which valve is sticking open.

This has only happened twice and about 10,000 miles apart. It has to be a sticky valve since it stopped by itself both times. Neither time did it cause enough air pressure loss to show on either air gauge.
Both times that it happened I had no where to immediately pull over and the air noise (shrill whistle) would stop by the time I did.
Both times it happened when it was very wet outside previous to starting off.
It sounds like it is coming from forward of the driver's seat and not from the passenger side toward the rear, where you normally hear an occasional burst of air being released.
Once I can identify which valve it is, then I can replace it or bring it in somewhere to have it done.
Tom

[gripper]

Quote:

Originally Posted by Roadking I'm no expert here, only passing on what I remember from reading in the past. I downloaded the South dakota CDL air brake certification study guide from the South Dakota DMV site. As I recall the South Dakota guide describes a series of tests which I believe some, or maybe all, would apply to any air brake system. I would guess most state DMV sites would have manuals to assist taking the Air brake certification test. Every time I read the manual, which I need to do again, I learn, or in the case of my CRS, relearn, something.

Thanks Roadking. You've peaked my interest enough to ask my service tech at the "Cat." shop, to walk me through what I need to look for.

Roland