Air drops to 80psi?

[eb99603]

Hey all. My S215 is leaking air. I hear the main tank "moan" once every 30 seconds or so after shutting off the bus and we slowly lose air pressure until the brake and aux gauges both read 80psi. Then it seems to hold steady.
Any ideas on where I should start looking?

Thanks!

[moosemanusa]

First thing would be soapy water!

Get out the spray bottle, fill up and start spraying (with the bus on or airline plugged in)..

That will help locate the leak, probably just a bad checkvalve

[eb99603]

Yeah I'm all too familiar with the soapy water routine. My bus has about a dozen check valves buried in various locations. Looking for any ideas on which might be the culprit or which system runs on 80 psi.

[Dave5Cs]

Won't find a bad check valve with SW its internal. if you can hear one spray around that area. Sounds like a check-valve stuck in the open position or a air regulator if it comes down to 80lbs and then stops.

[moosemanusa]

Sorry of to stated the obvious but its the start point, you're have various check valves that are set to open at minimum PSI's and close at other's..

So the fact you're losing air down to a set number and then staying constant would mean one of those is the culprit.

I had a quick look around for the air schematic online (94 Setra) but no joy, did see some references to an air flow sensor switch that operates at 80psi!

[eb99603]

Cool. Thanks guys. Once I get out of this electrical panel I'll pull out the manual and start flipping pages looking for regulators and check valves.

[eb99603]

A few things of note.

1) It looks like my bus is losing air out of the suspension on the driver's side front, rear, and tag bags. I know I have a leaky leveling valve up front, but it seems odd I'd have 3 all on the same side of the bus, all at the same time.

2) When I lose air in the system, I lose door pressure. This sucks. Clearly I have a bad check valve going into the door lines (or a leak in the door lines). Once I find that check valve, I'm going to put a gauge and a shutoff valve before it so I can figure this out once and for all.

3) The PR4 pressure retaining valves in my bus seem to be functioning correctly. A leak exists somewhere, and once we hit 85 psi those valves stop supplying air to the leaker.

[Jon]

Your leak is clearly on the accessory side of the pneumatic system. My guess is while the secondary and primary brake systems are holding air thanks to the protection valve(s) you have a leak or leaks on the accessory side.

[robertglines1]

Ball valves installed in various auxiliary lines will help you isolate fast and will aid in future. Mice love the plastic (soy based) air lines in a bus. Voice of experience here.  little holes in hidden   lines are a bitch. I'm always suspect of push fittings and replace them with compression. wiggle the push fittings when using soap/ also sensitive to pressure as they may not leak until pressure gets to a certain lower point and they loose seal.Check tanks around bottom and any straps(under them)  Just some thoughts.   Bob

[luvrbus]

LOL I am sick of the push in fitting also Bob they are a real PITA

[Lee Bradley]

Try turning the emergency door valve.  It should open the door and shut off air to the door. I don't expect your door cylinder to hold air. My door cylinder leaks air but if I open the emergency door valve the system air will hold for weeks. 

[eb99603]

I think my cylinder holds air after I put a new repair kit in it. But it's a decent idea nonetheless. I'll throw a gauge in after the first shutoff valve after the tank, and flip the valve. We'll see if the repair kit is working like I think (hope) it is.

And then I have to work on repairing the shop-air connection on the bus. The fitting mounted in the engine compartment doesn't work. Must be plugged somewhere along the line. Fixing that and using my air compressor will go a long way toward isolating any leaks on the rear suspension.

[robertglines1]

 air connection. should have one in front for emergency use. Prob in steering box compartment. Prob got Schroeder valve on it now. I change them out to except air fitting with check valve. or in line ball valve.   

[eb99603]

The only air connection I have in the front of the bus is for recharging the luggage compartments by utilizing the spare tire. And my recently acquired air lines diagrams from MCI/Setra confirm - the only external connection is at the back.

Say, all these ball valves you put in - where do you get them? I did a cursory Google search this morning for DOT/SAE ball valves and came up empty handed.

[John Z]

Am also interested in a couple ball valves. My wiper valves are leaking a little, and I'd like to shut the air off to them when I'm not using them. I know, I know I should fix the wiper valves. It is on my list, just not near the top yet.