What is this? A warning or???

jav9956 · March 21, 2016, 10:48:15 AM

This little guy in the spare tire storage area makes noise once the bus is turned off. It may be going when the bus is on but it is only really noticeable when the bus is off and air is being released.

There is clearly air coming out of the apparatus. Is it supposed to be? Is it supposed to be a warning sound or normal function (doesn't sound normal)? What would the corrective action be if there is an issue?

I know it is this unit because I tracked it down by ear and when I put my finger in the oriphice the noise stopped.

Anyhow, it would be good to know what is going on if anyone has insight.

Tikvah · March 21, 2016, 10:59:47 AM

That's a Quick Relief Valve. When you set your parking brake, the air blows out there.
I just had one go bad a few months ago, it literally left me on the side of the road. Once that valve ruptures, and the air bleeds out, your parking brakes are set.

Somebody on this forum got me home with this suggestion. Push a wine cork in the hole and wrap tightly with some zip ties. Sounds crazy, but it worked.

$25 part and easy to change.

If it's blowing air on the road you better find a safe place to park NOW

jav9956 · March 21, 2016, 11:33:16 AM

That makes sense, thank you for the info! Learning a lot about this old bus.

When the air bleeds out should it be making a loud humming noise for an extended period of time?

buswarrior · March 21, 2016, 12:08:07 PM

Air leaks often make sounds.

It is the way of pneumatics to talk, whine and whistle at you.

Understand the cork trick renders the valve non-functional for its intended purpose... that's fancy talk for the brakes attached to it won't work right....

Hang on before you go changing good parts and end up with the same trouble...

It's job is to empty a circuit when the pressure applied to it reduces. If air is escaping, once the air it is intended to evacuate has left, you have something deeper down the line leaking air into the circuit that it has evacuated. The driver's control valve would be my first suspicion, as it's the next place there is pressurized air.

Clear as mud?

Two tests and report back:

Air up the coach, block the wheels, release the parking brake, and confirm it doesn't leak in that configuration. Soap bubbles are helpful.

See if turning or gently leaning/manipulating the parking brake control changes the noise.

happy coaching!
buswarrior

jav9956 · March 21, 2016, 12:20:25 PM

Buswarrior-

I will definitely try those suggestions, I won't be back at the bus till this coming weekend but when I pull it out 20 ft to work on it I will try the two tests and let you know what happens.

buswarrior · March 21, 2016, 12:50:39 PM

And, the more I think about it...

the driver's parking control valve might be seeping into the circuit,

or

the parking diaphragm in one/both of the DD3 brake chambers might be leaking by into the service side, and then finding its way out that QR-1.

How strong is the breeze? Do you get any air out the exhaust on the bottom of the brake pedal valve too?

The joys of catching up the "deferred maintenance" of the previous owners....

happy coaching!
buswarrior

opus · March 21, 2016, 06:42:16 PM

I'd be more likely to have 12 spare quick relief valves than a wine cork!

luvrbus · March 21, 2016, 07:10:18 PM

The QR-1 should have no air leaking with the parking brake applied or once released he has a air feed coming from another valve some where most likely the PBV

jav9956 · March 21, 2016, 10:43:43 PM

I think I am going to order the replacement part, it sounds like a good part to have for as cheap as it is.

I am still going to try doing the tests bus warrior suggested. This is a good opportunity to learn a little more about the air system. I also need to take apart the left wiper assembly because I know there is something not seating right as there is definitely a leak there. The whole air system is really interesting.