Aux Air System Leaks

[MyPrevost]

My 1997 Liberty Classic has developed a leak in the auxiliary air system. The small electric compressor used to activate approximately every 12 hours, but now it runs every 15 to 20 minutes. The compressor operates until the pressure reaches 75 PSI, then stops, and starts again at 55 to 60 PSI.

The only components I know of that are powered by this compressor are the bed lift, the black dump valve, and the gray bypass valve. I’ve checked the control valves and fittings for these three components and haven’t found any leaks. I don’t have air-operated pocket doors.

What could I be overlooking?

Lee

[MyPrevost]

Lee,

The air feeds for these lines are located in the driver’s steering bay.

Air exits from this “Christmas tree” at the shut-off valve on the left.

It then flows into this manifold, from which it distributes to the bed, chair, and other components.

Make sure to use soapy water to check all these connections for leaks.

I hope this information helps.

Mike

[MyPrevost]

Lee,

Don’t forget to consider the floor slide/step cover, the entry door lock, and the driver’s seat. You might also want to check the generator airbags, air conditioner bellows, and the engine fan bag. The valve above the engine doors was leaking on my unit, and it may still be an issue.

Got it!

2008 Liberty DS XL2
2023 Denali Ultimate
My sixth Prevost

[MyPrevost]

Roger,

I believe the floor/step cover and door lock are operated by air produced when the engine is running. I will trace the hoses and see what I can find out.

Lee

[MyPrevost]

And don’t forget about the leveling air bags. If there’s any air leak related to the leveling air bags, it will lose air, and the auxiliary tank will need to be refilled.

[MyPrevost]

I have isolated the problem. I removed and capped the air hoses at the manifold, as suggested by MangoMike. The hose leading to the gray bypass and black dump valves is the source of the issue. Since capping that line, the compressor hasn’t run for over three hours.

Tomorrow, I will investigate that air line further.

The air lines on my manifold are as follows:

Fat Hose: Air IN from the auxiliary compressor
Fat Hose: Air OUT to the Prevost system (via the converter valve)
Thin Hose: Out to the step floor cover valve
Thin Hose: Out to the bed lift valve
Thin Hose: Out to the waste dump valves
Fat Hose: Out to somewhere under the dash—I’m not sure what it is yet.

[MyPrevost]

Has anyone rebuilt the small compressor located in the front left of the coach? I replaced it and kept the old one, and I’ve looked into getting a rebuild kit. However, I haven’t yet mustered the courage to order it since I have no idea what the process will involve.

Lew

[MyPrevost]

If it’s a Thomas compressor, the cost to rebuild it is roughly the same as replacing it. I understand it can be difficult, but it seems companies prefer to dispose of items rather than repair them. For mine, they quoted over $200 for the rebuild kit, while I was able to purchase a pancake compressor for $160.

• This reply was modified 2 months ago by MyPrevost.

[MyPrevost]

Lee,

Any component that operates from the auxiliary tank will trigger your auxiliary compressor to run if the pressure drops after the engine shuts down. The air slide receives its air from the auxiliary tank rather than directly from the engine compressor. Be sure to inspect the air slide regulator (located in the steering bay) using soapy water. Mine had a leak, and I resolved it by taking it apart and replacing an O-ring.

Tom Chilcote
Trans-Specialists RV Batteries
tom@transpspecialists.net

[MyPrevost]

Dale,

Did you install the pancake compressor in the steering bay? How did you mount it? What pressure can it achieve? I’m considering switching my air reel to that if it can provide enough pressure to inflate tires to 110 lbs. Would you be able to share a picture?

Lew

[MyPrevost]

Dale: Make, model and source please. I do not have a aux compressor, but would like to get one. 12V

[MyPrevost]

Tom,

Where is the auxiliary air tank located?

My air line is set up as follows:

Aux Compressor > Pressure Switch > Distribution Manifold > Converter Valve > Prevost System.

The manifold distributes air to the bed lift, sliding floor, dump valves, and another component under the dash.

The converter valve allows me to separate the auxiliary air from the Prevost system, but I’m not sure why it connects to the Prevost system at all. Does anyone have insights on this?

[MyPrevost]

Lew,

I installed the pancake compressor in the generator bay (the first bay on the port side) to keep the steering bay tidy. I prefer a clean steering bay, especially since there’s a sign that says, “Keep this bay clean.” Additionally, I’ve given the steering bay to Jan to store her purchases while we’re traveling.

Notes: I bought it at Sam’s Club. It shuts off at 135 pounds and operates on 120VAC. I’m using a water filter and a 50-foot hose, and I take it out to carry it to the trailer if it needs air or if someone else requires it.

One of the things I appreciate most about it is that after the bus has been sitting for a while, I can simply turn on the compressor. Once the tanks are full, I can turn the key switch one click, and the bus will air up without needing to start the Detroit engine.

 

[MyPrevost]

Lee,

The “someplace under the dash” is likely for the air-operated louvers that control airflow to the cruise airs located behind the bumper.

MM

 

[MyPrevost]

Lee,
We need Jon to jump in here, same make and year, I’m confused on your setup. Are you saying that the aux compressor does not feed the aux tank? Unless Liberty does something different, the job of the aux compressor is to maintain aux tank pressure to run all the air needs we have been discussing, while the engine is shutdown.

My aux tank in located up front, to answer your question.

Jon?
Tom Chilcote
Trans-Specialists RV Batteries
tom@transpspecialists.net

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