Does 20PSI ring any bells?

[Pjanecke]

I’m hunting for a leak or leaks. No hissing. Brake front and rear holds air at 110psi forever. Suspension is dumped.
Coach airs up quick to 120Psi from engine compressor. When you shut down the engine, it drains about 1psi per minute down to zero with no pause at 60psi.

My aux junair compressor can’t get past 20psi.

I hooked my Viair tire compressor to the shrader valve at the engine and it also can’t get past 20psi (exactly, on the nose, reading at the grey/black dump controls).

Is there any device that is throttled at 20psi?

All new airbags, new drive brake pots, new air dryer, mechanic said PPV valve above dryer is not leaking.

I haven’t checked the air steps for leaks, although they work when there’s enough air.

Any ideas?

[Rick]

Going all the way to zero without pause indicates a leak in the brake system. Are both gauges going to zero together?

[Pjanecke]

Sorry for the confusion - my front rear brake dash gauges hold steady for days after shutdown.
It’s my sewer valve gauge and my AutoAwn (air awning) gauge that both drop steadily to zero after shutdown.

[Bill Pape]

sounds like a leak in the auxiliary or wet tank,
Now the fun starts, anywhere but the brakes.
Air suspension, air horns, seats,
dump valves, water purge system, air dryer, etc

[giderich]

Originally Posted by Pjanecke

Sorry for the confusion - my front rear brake dash gauges hold steady for days after shutdown.
It’s my sewer valve gauge and my AutoAwn (air awning) gauge that both drop steadily to zero after shutdown.

Auxiliary system air leaks; air toilet, air slide(s), air step, air slide over entry, air horns, air sewer dump valves, air solenoid for steering tag axle, air purge valves on aux tank & wet tank, Allen Air solenoid valves (horns), low pressure air switches (30 psi & 60 psi), Baby (1 gallon) slide/toilet air tank for slide/toilet (8 or 10 places for leaks), several one-way check valves in systems (look at air diagram). Do not over-look the Air compressor, air dryer, air governor, and associated plumbing. Also check the 3 (three) WM47P suspension dump valves, 3 HCVs (Height Control Valves) and double check the air lines to each of the 10 air bags (springs). Leaky pressure protection valves. (see air diagram).


Several small leaks can add up to a large leak. Use shop air (not that that silly 12 volt Viair) to pressurize the system since it will take a few hours it address all the air leak possibilities.

[Mallie Lennon]

I had a couple of major leaks over years. First would dump the aux in a few minutes and i could hear it when turned the engine off. I was the diaphram on the pressure protection valve next to the dryer. The other would take a while, but was big enought the aux compressor could not build air, and strangly I could not hear it. Engine would build air OK. Actually though it was the aux compressor. Ened up being a small line had pulled out of a push fitting.
I would suggest you get it blocked up and roll under as soon as you turn the engiine off, and everything is quite. Might be able to hear it.

[irmagoo]

i had about 4 - 5 leaks on dump vlv. piping/fittings alone all were small but all ad up
i just fix them as i find-um,,,

[SNOWBIRD]

I had the exact same symptoms, could not get over 20psi with the aux compressor. My leak ended up being the PPV right by the schrader valve in the engine compartment. Its easy to get to so I hope yours is the same.

[Pjanecke]

Thanks, I’ll check that PPV behind shredder valve this afternoon.
This morning I checked the steps, no leaks under there. But I couldn’t locate the low pressure switch? Anyone know where that’s hidden?
I also capped the air feed to the dump console, eliminating their involvement - no change.

[Pjanecke]

Originally Posted by SNOWBIRD

I had the exact same symptoms, could not get over 20psi with the aux compressor. My leak ended up being the PPV right by the schrader valve in the engine compartment. Its easy to get to so I hope yours is the same.

Thx for the lead - unfortunately the line from my Shrader valve heads directly forward through the bulkhead. So l’ll need to get the bus on stands to investigate it.

I did find leaks at the footrest slide and door lock solenoids - waiting for parts to arrive.

Still can’t find where the pressure switch for the steps is hidden?