[Miles]

from empty, about 5 to 10 minutes. from cut in to full, about 2 minutes

[Archived]

Miles,

There is a leak or you have not closed the yellow valve. This blending of AUX and Prevost systems has some drawbacks.

Another cause is a leaking, plugged, or broken check valve which in this case would not hold pressure in system.

You don’t mention what part you changed out ?

Where did you drain system ?

AL

[AL]

Thanks Charles, hopfully we’ll be there soon.

Al,

We changed the check vavle, and gen air bags regulator. ( I’m Larry’s son so you helped with both of those) We fill the aux side with the prevost vavle then turn the vavle back off. The three hour fill time, to 70 psi, was with the prevost vavle closed. we drained through the pancake tank, wheel style drain.

thanks for the quick responses

Miles

[Dick]

The new heat relieving regulator…… hoses in correct ports ?

I’am also going to suggest you change the wheel style drain valve as these are on the hit list. The valve replacement can be purchased any where . Finding a skinny one might be a hunt.

Last idea .. If you drained the system down have you lost the seal on the Norgren air moisture valve in the drivers bay.?

This is the one that has a water drain under the bus.

I’am trying to help… posting suggestions as somewhere is the source of your leak.

[Richard]

Miles,

Mine will go from empty to full, 120 lbs in about 3 or 4 minutes. Mine being only a 3 gallon tank fills quickly. You have some leaks, but at 5 lbs. an hour, that’s not all that bad. If you had a really bad leak that keeps the compressor running long, it would show when you blend the Prevost air and charge the Marathon tank, you would see a quick loss of air.

So I think your problem is compressor related, they do go bad. Unhook the supply line and run the compressor to see how much volume you have. I would think if the check valve was bad and not letting air pass to the supply line, it would make too much pressure and open the relief valve and you would hear that.

[AL]

If you have a way of monitoring the current draw from the compressor you can get a clue as to the compressor health.

On my coach I pressurize the Prevost accessory tank and unlike Marathon I do not have a dedicated house air tank. While the tank volumes may differ the general principle of filling as relates to current draw is going to be the same. If I start with zero pressure in the accessory tank my initial current draw is about 7 amps. It takes 3 minutes, 40 seconds to reach 80 PSI which is my cut out point. By that pressure the compressor is drawing 12 amps showing it is working harder.

If you can monitor your compressor current draw, and measure time to cut off and compare that to what others experience with their Marathon you will learn some clues to point toward your problem. If your compressor starts off with a high current draw for example it is working against an obstruction such as a closed check valve. If the current draw is initially high, and then you see it drop or remain constant that shows the restriction has opened or the back pressure of the system in now uniform on both sides of the restriction.

The time the compressor runs also tells what is going on to an extent.

[Dale]

Have been chasing the same type of leak for months. Started with check valve and regulator for the engine belt bags. Still leaked. Installed an air guage on the dash for the aux system to see how much it was leaking. 5-lbs/hr. Finally found that the 19 year old directional valve to the floor slide seemd to be the culprit.Replaced it and with new valve, leak reduced to 3-lbs/hr. Sent back to Norgren and they sent a new one again. Leak reduced to about 2-lbs/hr. Sent it back again for them to bench test the leak (leaking from the exhuast ports depending on the position of the floor, port 3 or 5) They said bench test was within their specs ???? Thought there should not be any leaks ????. Now at a loss connected my JUN-AIR compressor for my awning into the aux system as I have not found a valve that does not leak. From empty it took about 12 – 15 minutes to bring up to 105 lbs. If from full the compressor runs 2-3 times a day for approximatly 2 minutes to bring tank up to 105 lbs. Still looking for a solution as to how to stop the leaks. Have goen through quarts of bubbles and can only find the leak on the replaced valve! Any suggestions?

[Archived]

Thanks everyone for your suggestions! very helpful, i will try the things you guys have listed and hopfully have some luck.

Thanks again.

Miles

[Dorel]

One of the issues with the pneumatic systems in our coaches is age. All the valves rely on rubber or rubber like compounds to seal valves against leaks. As the rubber ages it becomes less pliable and eventually leaks occur. The problem we have as our coaches age is there may be hundreds of places where minute leaks can occur, and while there may be no big leaks, the cumulative effect of many small ones will add up to a lot of leakage.

There is also the fact that any valve or seal has some sort of acceptable leak rate. Ideally nothing new should leak. But companies that sell parts of the pneumatic system all have factory tolerances which define acceptability. When Peter was having issues with his drive axle brake chambers leaking at the parking brake side Bendix acknowledged there is an allowable leak rate. As long as new parts leak less than that rate the part(s) are deemed acceptable.

We can all approach “leak free” for our coaches, but it is unlikely we will reach perfection. This is especially true unless we opt to change every single valve and pneumatic device on our coaches with bench tested parts. Then we also need to insure every fitting and connection is leak free, finally we need to inspect and replace every hose or air line that may have cracks or porosity due to age.

[Dale]

Jon,

Agree completely with your thoughts. A close friend of mine was an airline jet machanic. His feeling is that a neumatic or hydrolic valve that controls movement should not leak at all (that is one reason of many that makes airplanes crash). We could replace all as you state, but with poor tolorances from manufactures, with all new slightly leaking, would we not be in the same boat?

Richard

[Archived]

I cannot speak for others, but as my chassis is approaching its 10th year I am embarking on a long project that will replace every air bag, every Norgren valve, convert all push in fittings to compression and to create a manifold or manifold with individual circuit shut off valves so it makes future service and leak detection easier.

I know the house has a lot of potential leakers ranging from the pocket door valves and mechanisms to the floor slide, the bed lift to the seat so I will include some work on those systems as well. I am in no rush, and unlike past forays into chasing leaks I am just going to make sure the work I do is leak free, and in the process I hope to catch the bulk of the leaks. I have found it really takes too long to do leak detection so by doing a scorched earth update to the pneumatic systems maybe I will catch the vast majority of them.

It would be really nice if as our coaches age leaks would pop up in one place or another and be big enough to be easily revealed, but that is not the real world. Except for certain components most leaks are the tiny ones that collectively add up, but individually are almost meaningless.

[Dick]

Is the real issue of air leaks that at some point your compressor or aux. compressor cannot keep up with the leaks which creates some type of safety issue? At what point do you do what Jon is doing and simply replace everything, 10-years or simply when the air leaks overwhelm your compressors?

Also, is this issue unique to Prevost or do other DP have this issue as well?

[Dick]

Tim: Its more than the compressor trying to keep up; the issue cascades into other issues. If you have leaks going down the road with the Detriot Diesel running there is LOTS of compressed air so leaks are probably rarely an issue.

But if you stop and dry camp (relying on the generator to recharge the batteries) the compressor running all the time will eventually result in the generator running to recharge the batteries which have now be discharged by the compressor. Also the compressor running every few minutes is annoying to most people.

If you’re camping with 50amp service the electricity is someone else’s problem, you just have the annoying compressor going on and off.

If you’re plugged in at home, then you’re paying for the electricity to run the compressor regularly to replace the wasted compressed air.

[Dorel]

Dick if you are parked at home you do not need aux comp on with no slides on coach turnit off , I have had three prevosts replaced every part and all where leak free for a long time , on my coach now I have done all fittings and manifolds and all parts are new do not have to worry for ten years now , like Jon or him like me I hate leaks so I replace all things that can leak , unless I use air my aux comp never comes on that’s the way I like it

[Archived]

Peter & Jon,

If you don’t mind me asking, what did it cost (or will cost) to get your coach leak-free? From reading the posts, I have a general understanding what needs to be replaced or upgraded, but did you do it yourself or have a Prevost service center do it?

I see Jon is doing it himself saving a lot of $$, but if you have to use a service center, I’m just curious on the general price since I “will” be buying a 13-15 year old coach and most likely will have to upgrade the coach’s air systems.