Relief Valve?

[Bluthebus00]

Hey guys, we have a 25' front engine Bluebird transit bus. Love it to death!

We had very frigid temps in the north east for approximately a 3 week period. Then the temperatures randomly jumped to nearly the 70s for a couple days.

I took this opportunity to start the bus and move it around to check everything out. It's been sitting in our driveway for about 3 months without being started while we worked on the interior.

The bus started up without hesitation and ran great! I immediately noticed the sound of a large air leak, large enough where the compressor struggled to keep up. I traced the leak to this valve(see attached pic). I wanted to show this valve to some of the wizards on this awesome forum who may know what this is. Bus never had this before. Yay for surprises. Per the gauges, this valve appears to be tied to the front air tank. The rear tank fills to about 115-120psi. The front struggles to get past 100. Previously both would hit 120psi quickly before the cutout.

To me, the newbie, this valve looks like a bleeder or relief valve. In the slit, there is a small hole where the air is released with a decent amount of pressure. It is also threaded suggesting I can adjust or close it. That said, I'd rater get some insight before I start touching things I don't yet understand.

I've built cars and and love the automotive world but diesels and air brakes are a new experience for me

Thoughts? Thanks everyone!

[Jolly Roger bus 223]

A pic of it spitting water or an object pointing to where it is spitting air at this point would help us say just replace the valve or (not usually?your tank is bad?)
That valve itself should break before the tank does?
But I don't want to say go find a 20$ dollar valve if your 200$ tank threads are the problem.
Do you see/feel a crack in the brass valve that the air is coming out of?
Or is it where it is threaded/connected into the tank itself?
Usually not the tank fittings but it does happen.

[Jolly Roger bus 223]

Also put some dish soap in a spray bottle(more soap than water) and spray all the air components.
Compressed air can be difficult if you don't know the system?
You stic your hand up and feel air so you say it's coming from here and you fix that and all of a sudden it's coming from a fitting an inch over, fix that and it's still there?
It was actually coming from a fitting 12"s away and at 120'psi you felt high pressure air on your hand and said this is where it's at?
Most use plastic air lines to and from each beginning and end point that are more prone to break in the cold than brass or steel?
But those valves do go bad overtime also.

[Bluthebus00]

Jolly Rodger Bus,


Thanks for the quick reply! Here's a couple pics illustrating where the air is coming from. I have a video but it is too large to upload here.

The one picture labeled "diagram" is supposed to be an illustration of if you're laying on your back looking directly up at the valve pointed at you.

The blue circle in the middle is where the air is leaving the system.

The second picture has red lines illustrating exactly where the air was coming from.

No water or visible mist was seeping out of the valve, just dry air thus far. The air stream was hard to miss. It was unfortunately so strong it was blowing leaves from under the bus. I was able to put my finger right on it and slow it down.

I'll definitely take your advice and try spraying soapy water on the components to look for other additional leaks.

Originally Posted by Jolly Roger bus 223

Also put some dish soap in a spray bottle(more soap than water) and spray all the air components.
Compressed air can be difficult if you don't know the system?
You stic your hand up and feel air so you say it's coming from here and you fix that and all of a sudden it's coming from a fitting an inch over, fix that and it's still there?
It was actually coming from a fitting 12"s away and at 120'psi you felt high pressure air on your hand and said this is where it's at?
Most use plastic air lines to and from each beginning and end point that are more prone to break in the cold than brass or steel?
But those valves do go bad overtime also.