Help to locate an air leak.......

Hello,
My name is Michael Vargo and am a new owner of a 2012 Liberty H3 for a year now. My wife, daughter and I are very happy with our coach and know that staying with a Prevost is our only wish going forward. Not being a mechanically inclined individual, I do at times struggle with some minor repair issues. One that I seem to be struggling with currently is locating a small air leak somewhere that causes my compressor to constantly kick on. I have located a few valves that have been replaced and without question the issue is getting better ( meaning the air compressor is not kicking on as often) however, I still seem to have a leak somewhere. So my question is: has anyone discover a clever way to detect this air leak issue other then the traditional smoke gun, and or spray bottle with soapy water?

Thanks,
Mike-

Mike,

I had a one-way valve (located at compressor) that was leaking and causing a problem. I am sure you are aware that the most probable place for a leak is at the compressor or at the valve at each of the air operated components. I know this is not a direct answer to your question. The only time I had a Prevost shop check my system for leaks, they used a spray bottle. I have one of the electronic leak detectors, but I've actually found more leaks with a spray bottle.

Mike,

Air leaks are common with Prevost conversion ownership. Not all air leaks require attention.

Air leaks with our braking system are the most critical and almost always should be repaired. Even some braking system leaks are allowable. Push-on connectors will leak over time. Brake relay valve will leak over time. Brake chambers will leak over time. The DoT realizes a leak free system is not necessary to a fully functional braking system. The rate of leakage and what’s leaking are the important factors.

The leaks you’re chasing should not be brake system related. Your leaks can be the hardest to nail down given there are so many air operated devices on the auxiliary side (both Prevost and Liberty) and most of these are built to the same specifications as our braking components. So, where to start?

Before you begin to look for specific leaks, I highly recommend you start blocking systems to determine where you need to begin your detective work. I haven’t had the opportunity to look at a late model conversion to see how the converter configured their auxiliary air system. So, let make the following suggestions.

Follow the aux air compressor supply line as far as you can. Turn off the shutoff valve at the furthest shutoff valve before the supply line branches out (if it does at all). Does that affect the compressor cycling? It should not cycle at all, at least not for a very long time. If it does, work backwards toward the compressor to find the leak.

Prevost installed two converter air connection points in most coaches. One will be in the front air/electrical compartment. It will have a tag identifying it. In year’s past, the connection point had a yellow handled cut-off valve. The other tie point was on passenger side in or next to the engine bay. Assuming either valve is open, close them and see what impact that has on the cycling of the compressor. If the rate of cycling gets better, the problem is in the Prevost aux air system. This could be engine air bags, suspension components, slide seals, steering column adjustment, dash air pressure gauges, back-up camera door, or air horn (if factory equipped).

Converter’s may have air supplied to the step well slide, air horns, air seat, generator air bags, door slides, awnings, toilets, dump valves and possibly other items. You likely have a manifold or manifolds used to support these branch lines. Take a short piece of air hose, probably ¼” and attached an air gauge to one end. Now use this hose and gauge as a termination to take the place of each system connected to the manifold(s) until you discover what is contributing to your leak. After installing the termination, air up the system and then turn off the compressor and note the amount of air pressure drop over some defined period of time on the gauge you are using. This is easier and more precise than waiting for the compressor to cycle. Don’t be surprised if you have more than one system leaking.

Most converters installed their air systems assuming there would never be any leaks. I recommend that you break your aux air system into no less than two subsystems. Anything on the converter’s side of the aux air system that is not required when you are parked should be diverted to their own manifold that is supplied air through an ignition switch controlled valve. This is not hard. This alone is enough of fix for many coaches. A check valve or two may be necessary for directional air flow to the rest of the aux systems. Take for example a desire not to supply air to the Prevost aux system when parked but supplying Prevost air to everything when driving. A check valve can ensure air only flows in one direction. My air system is very basic and a good example. I have a check valve after my aux compressor’s air dryer that prevents Prevost air going to the aux compressor or its dryer. I have another check valve positioned so that my aux air goes to my generator air bags and Prevost slide seals but nothing else. My compressor might run once or twice a day for 15-20 seconds each time.

If you find your leaks are in your suspension system then we need to have another plan of attack.

As for leak detection tools, there are a few. Soapy water is good for many leaks. There are also special solutions for leak detection that are much thicker than soapy water and they show bubbles better. There are ultrasonic testers to hear the leak. I’ve never had much luck with them. There’s also the “Texas Bubbler” that a member came up with. This device will show bubbles with the slightest of downstream leak. I keep wanting to make one, but just haven’t yet.

Gill u r not giving the ultrasonic leak detector its fair assessment.

Yes they r not all created equal and yes they r a tool that u have to practice with to get proficient.

BUT if u get the right one and u practice with it it will become a more than equal tool to add to the arsenal. I wouldn't ever be without mine.

Another great option is replace the aux compressor with a California air unit. It is so quiet and the run cycle is so short it will allow u to live with a great deal more leakage for a lot longer hopefully giving u more time to hunt them down if that is what u so choose.

I would be the first to admit this is not a fix but if u own the bus for long enough and go through this dance enough times u will eventually agree its a fantastic option.

Where to buy the California air unit thanks jerry

I bought 2 from Amazon (Click Here) for a link to the one I bought.

Jerry,

I'm pretty sure California Air Tools is the company Joe is referring to. I've had one of these units for a couple years and it is quiet and fast.

http://www.californiaairtools.com/ul...r-compressors/

https://www.amazon.com/California-Ai...dp_ob_title_hi

I have a leak in my driver side rear. After key is turned off the bus settles on the left rear. Any good sources in Fort Worth Texas ?

I ment to ask for a good mechanic for air leak in Fort Worth?

Pablo,

Some leaks aren't too hard to find, others take talent and time. You might try Prevost, especially given they are in your back yard. If you do, just limit how much time they spend on the job. Some techs are pretty good at knowing the most probable causes.

The bird dog of leak isolation is our own Joe Camper and he makes house calls.

Can you lift your tag axle before turning off the coach and see if you still experience the leans? This will help isolate the location of the leak.

Hey Gil,

Sorry for the delayed response. I lifted my tag axle before I turned off the coach and it seems to be holding? it has stayed up for a day now.

Thanks Pablo.
2004 Prevost Royal

Pablo before u raised the tag did u go to level low and manually raise the rear of the bus up first?
. If not your results were potentially incorrect.

Without first going all up rear and u dump the tag the back squatts so much it may alter test results.

If after u try my suggestion and the lean is in fact gone away........... that means your lean is either.

The 2 position spool valve between the drive bags and the tag bag.

OR
The tag bag

OR

The tag bag ping tank ( football)

OR
A fitting or line associated with those components.

I did not do that. But after a day or two it did leak down. I read your explanation of the fix and I do not think I would be able to correct it myself.

It looks like I'm headed to the shop.

Thanks for the information.

Jeff Kruse
817-937-7688

You're close to the Prevost shop. I'd use them and make sure you are assigned a good air system tech. It shouldn't be too hard to troubleshoot based on what you've said.