Marathon Air compressor, How often does your compressor switch on when idle?

[Rickjack1216]

What is a good goal for a Marathon Air compressor cycling on and off when the the coach is idle. No pneumatic doors opening or closing etc. Of course the age of the coach matters but would a good goal be and when should one try chasing down an air leak and when is it time to just enjoy life?

[Gil_J]

2-3 times a day would be great. Keep in mind you have a lot of systems supported by Marathon air. Sadly, from the factory your slide seal system is probably not one of them if the coach has Prevost and not Valid slides. In a perfect world converters, probably all of them, would have done a better job of engineering their air system. You have the generator air bags, stepwell slide, driver's seat, air horns, air doors, possible air lock on the refrigerator, the Marathon water bay air stuff, and likely other air demand systems looking for Marathon air. The kicker is that being done smarter would not have been hard or costly. When parked, air in a well designed system would only supply air to those systems needing air when parked (generator bags, air doors, and slide seals).

[truxton]

Rick,

Unknown to some people Marathon has the best Aux air system going. Once you understand the logic the way they isolate their Aux air and don't mix with the Prevost air is a much easier way to find leaks.

2 to 3 times in a 24 hour period is not bad but you can do much better.

Also your Marathon Aux air keeps your slide seals full regardless if you have Prevost or Valid slides when parked. The sadly part of the previous post is he said from the factory. Prevost does not install Marathon aux air but after Marathon converts it they plumb the slides into their aux system. In your vintage you need to understand how the yellow valve they installed in your front run bay affects your aux system.

Later
bv

[Gil_J]

Bernie, I've corrected far too many Marathon's that did not have Marathon air provided to Prevost slides. All mid 2004 to 2006ish. I know it sucks to be wrong, but you are in this case.

Obviously my reference to the factory was the converter. Prevost doesn't sell a completed motohime.

[billybeaver]

On our 2001 Marathon, the aux compressor cycled about every 20 minutes when we bought it. First thing I did was to install shut off ball valves to each item/system serviced by that compressor. Not that hard to do and makes isolation of significant leaks a lot easier. Aux compressor now cycles 2 or 3 times a day. Highly recommend that as step one. Mike

[Joe Camper]

Rick there is a device called Amprobe. Amazon has it. It is a very handy tool.

Check around the control manifold for the slides up on the bay ceiling including the exhaust ports.

There is a aux air manifold prevo has on all chassis. On xl its in the small compartment after the tag pass side. On h its way in the RR engine bay door between frame and motor. Way in there hiding round the forward corner. Check there.

Find the controls for the pocket doors and sniff those. Some r behind the dresser drawrers on Marathon. Sniff the pressure reg for the aux air.

What is it set at if its 100+ see what the minimum pressure required for your stuff and turn it down to a lower pressure if it is. Say 60 on 80 off is a safe jumping off point for that adjustment.

Getting this aspect squared away is some serious braggin rights at rallys and get togeathers. Good luck.

Some r so quiet almost cant here them. If it dont wake u at night allowing once every couple hrs wont burn it up and at that rate of loss if u have all your spots identified to look and u got the tool u will here that.

Then there is some chassis, great buses, where guys work real hard to get it to hold at 2 or 3 times a day best they can get it. Other chassis hold 120 for weeks.

My pete I still havent been able to seal it up. At 70° i loose 10lb overnight. I been going over it for 5 years now.

The patient needs to be cooperative.

When tasked with this I sell the coustomer 2 hrs let me have 2 hrs at that point based on results we can decide to stop or go on another bit of time.

[truxton]

Gil,

Your quick with the tongue today. I'm not going to argue with you about your broad range of a 3 year span of Marathons.

I guess the yellow valve Marathon put in does nothing.

Later
bv

[tnjet]

I think they must have changed along the way. My 2007 H3 slides seals (valid) are aired by my Prevost air system. Here is how my coach is configured.

Prevost Air:
Engine Belt Tensioner
Driver's Seat
Rear (back-up) light door
Slide Seals

Marathon Air:
Step Slide
Air Doors
Refrigerator Lock
Sewer Hose and Door
TV lift lock

I believe my train horn is on the Prevost Air system.

[Gil_J]

I think they must have changed along the way. My 2007 H3 slides seals (valid) are aired by my Prevost air system. Here is how my coach is configured.

Prevost Air:
Engine Belt Tensioner
Driver's Seat
Rear (back-up) light door
Slide Seals

Marathon Air:
Step Slide
Air Doors
Refrigerator Lock
Sewer Hose and Door
TV lift lock

I believe my train horn is on the Prevost Air system.

I've never looked at Valid slide plumbing enough to know it's source if air. Given its not a Prevost supplied system, I expected to be Marathon supplied. I guess Valid must have completed its air system when they install their slides.

It would be unusual for seat air or air horn air to be Prevost supplied. Air systems vary enough that it wouldn't surprise me.

[Rickjack1216]

Thanks Gil. I have noticed that my valid slide seals do lose their pressure when the coach sits idle for a couple of weeks even if the marathon air side stays pressurize. I'm assuming that's what your were referring to regarding the factory slide seal.
Rick

[Rickjack1216]

bv,
I notice that on the dash the three air gauges R, F and Aux are all down real low after several weeks of just sitting even with the marathon air at around 100. When you mention Marathon Aux air is that different aux air from the dash Prevost aux air gauge on the dash? My Valid slides which were inflated and secure when parking the coach several weeks ago now say inflating on both valid controls in the coach and the slides are in and haven't moved since I parked it. The yellow valve in the fuse bay under the driver is a blue air line and the marathon air lines are all black. I don't believe the slide air is connected to the marathon air? is that typical in an 06 Marathon, 05 prevost?

[Rickjack1216]

Gil,
That would make sense since the Slide hose off the slide valve under the driver in the fuse bay is blue and all the Marathon air seems to be black and on the prevost dash Aux air is at 0 while marathon air is at 100. I'm assuming since I haven't started it in a while the seals have deflated. Am I correct?
R

[Rickjack1216]

Mike,
Are all the systems and supply hosed located in one place. My compressor is in the generator bay on top of the generator in the back and my green air tank is in the front of the bus behind the bumper which is accessible when the bumper is down. I don't see that many hoses coming off of the air tank and they're definitely labeled. where did you install your valves?
R

[Rickjack1216]

thanks for the info. I'll work on your list. Obviously one must be up for the challenge. Fortunately I like the game.
Thanks,
Rick

[Rickjack1216]

Your list seems to match up with what I've found on my 2006 Marathon with Valid Slides. I notice my Bathroom air slide door loses air sometimes after several days and I need to push the open and close button to re-pressure. Probably a good source to look for my first leak. Do you know where the air valve for that door may be located?
Thanks,
Rick

[tnjet]

gil would know, but I believe the slide seals have check valves on them and should stay aired without any Prevost (or Marathon) air pressure.

[Joe Camper]

Look for pocket door controls behind the drawers in the bedroom dresser or the rear panel of a closet in bath hall or bedroom.

[Hoffman]

I have check valves on the slide seals, they never loose air (except for the back one which is split and wont hold any air). I've shut off the back seal due to it's operational 'challenges'. Strangely that slide does not leak, but that's another story for another post.

I get 18 hrs on Marathon air with a single pump cycle. Before I worked on it, i think it was 18minutes/cycle.

I think the best lesson from this thread is that there's a bit of variability amongst the finishers AND amongst different vintages. So goes a custom coach. Attached is a diagram of my air system, might be helpful for those trying to understand how it works. (at last on a ~2001 Marathon).18048

[Gil_J]

Rick and TNJET, I might have access to a Valid slide equipped coach next week. I'll try to see how the slide is plumbed. If it's like a Prevost slide, the fix is pretty easy.

[Rickjack1216]

will do. thanks,
Rick

[Rickjack1216]

Thanks Gil,
Rick (2006 Marathon 984)

[Rickjack1216]

Joe,
Diagram seems to match up perfectly with my coach. Where did you find the biggest problems areas on the Prevost air side regarding air leaks?
Rick

[Hoffman]

On the Marathon system, the joey bed system was a big issue. Not everyone has an air driven joey bed in bay1. The Marathon air tank drain valve was a big issue, so I replaced it with a ball valve solution. Pressure regulator on generator feet had to be replaced. I also have a Slideout TV in master which is Marathon Air driven. The regulator on the TV was also a big issue so replaced it. I recall replacing some pushin connectors on various locations. The Pocket doors were strangely solid.

[Joe Camper]

Rick I think u r refering to the step slide and that is marathon.

That could leak a few different ways not counting the 2 push in fittings attatched directly to the ram. Alot of Marathon step slides r boxed in from underneath when its out door open u r on the ground looking in underneeth it, cant see it LOL. SOMETIMES. They make it so u can stand on it when its out and thats what it takes. Then the one on the bottom of the ram u have to look through a jungle of stuff attatched to the underside of the drivers floor. From that compartment under the driver.

It needs to hold pressure to keep it in as well as pressure to hold it out. The regulator is in the compartment under the drivers seat. Marathon uses a manifold thats plastic for aux stuff in there and it has swivel push in fittings that usually r pretty good. The ram can leak 2 different ways besides the fittings. If it leaks from the o ring on the ram it will leak right there at the steps. If the bottom of the ram starts leaking it will bleed backwards and come out the exhaust port on the electric over air control. Thats prob could be a small blue Mac valve and close to the regulator Im guessing on those things depending but all generally helpful i think.

Buy an Amprobe u will love it.

Sometimes a ram leak is a project. If its leaking when its in and u dont use it when your camping putting a shut off on it may be the solution if acess is less than desirable or unless cost is not as important as wanting it right. Unless its really bad and loud that u need to stop.

Good luck

[BGLogistics]

My step slide leaks thru the electric over air control only in retracted position. I knew it did but didn't realize how much until repurposing the 3rd air press dash gauge from the old Howard "active steer" system. Plumbed it into aux air system.

Already bought an electric DC air solenoid valve to install in 1/4" aux air line to step slide. Gonna use the old Howard "active steer" 12v switch on dash for on/off. Wiring is already there in steering bay.

All I lack is the 1/4" fittings to the valve. Foolishly attempted to get them Friday (Black Friday) and access to Fleetpride was impossible. Traffic backed up for over a mile in both directions. Between an outlet mall and a shopping district.

[Joe Camper]

Bill if it leaks, only in the retracted position, (big clue) and then as u say u hear it at that valve AND if its out the little pouris filter on that valve that is the exhaust port and there is nothing wrong with it. Its the o ring on the bottom of the ram in the cilinder thats leaking that just happens to be where it is coming out. Do u understand?

[BGLogistics]

Yes. You or Gil told me that awhile ago. Slide still works fine, just wanna do this to stop the leak since it's an easy addition. I really won't need to turn it (air supply) off until slide is retracted.

[BGLogistics]

Redneck fix complete! Tee is for the dash air pressure gauge, followed by 12v DC NC solenoid to allow air to step slide regulator. Works as I had hoped. http://forum.prevostownersgroup.com/attachment.php?attachmentid=18060&stc=1

[Joe Camper]

It finaly sunk in what u did. Briliant. U had an electrily controled air valve for your howard steering on off switch left over from when u removed the rest of it and u use it to turn the air off to the step slide when its in. And its all right there. Very nice Very good.

Does it stay put or not with no air on it? I guess if it did u just flick that switch for an instant and it sucks back in.

So noted leaky step slide 60 points.

[BGLogistics]

Joe I had the switch wiring and the air line to dash already there. I ordered the solenoid valve $12.

I'll take the 60 points :-).

Yes slide stays put in either position without air.

[Gil_J]

Redneck fix complete! Tee is for the dash air pressure gauge, followed by 12v DC NC solenoid to allow air to step slide regulator. Works as I had hoped. http://forum.prevostownersgroup.com/attachment.php?attachmentid=18060&stc=1

Effective easy fix. Good work Billy!

[Rickjack1216]

Joe,
Do you use the headphones with the Amprobe along with the extension tube?

[Hoffman]

The headphones are only necessary when searching out noises while the engine is running. My air leaks didn't require the engine to be running to diagnose.
The extension tube is very useful to bend around corners in tight compartments and narrow the focus of the tool on specific components.

Besides the Amprobe, the Marksman II is another great tool for this task.

[Rickjack1216]

Joe,
I'll put checking the Step slide on my list. Never thought of looking from the bottom with it out while the door is open. I'm building a metal garage climate controlled building for the bus. should be done soon. Inside with the insulation it's real quite unlike in my driveway right now. I have an Inficon Whisper Ultrasonic detector that looks exactly like the Amprobe, headphones and all and I'm sure it will be alot easier in a quite environment to help find these small leaks.
thanks,
Rick

[Rickjack1216]

http://forum.prevostownersgroup.com/attachment.php?attachmentid=18069&stc=1

[Hoffman]

Rick,
To find my leaks, i set mine to the most sensitive settting, and then point it into general cavity areas. If any leaks in that area the tool will detect. If leaks are detected, then turn down the sensitivity and do a more fine tuned search for the specific fitting/junction/etc. But with the most sensitive setting, one can easily determine if a given cabinet/bay needs further searching.
Good luck.

[Rickjack1216]

Thanks for the info. Always enjoy the game and the feeling of victory.

[Joe Camper]

18070

Here is what I use. U cant use it without headphones they would be required kit.

[MusicianTrader]

Am i correct to assume that the Aux air is ONLY for aux items?
That it does not provide air for chassis air bags?
Forgive me for my silly question...but if this is so...to replenish the air in chassis 1 must turn bus on then?

Patrick

[Hoffman]

AUX air takes care of all Prevost air items OTHER than brakes. So AUX does cover suspension.

In order to raise the chassis, you'd likely have to run the engine. However for my leveling system (HWH) I can operate the values by simply dumping some air from the Marathon system into the AUX system. This is necessary when I've been sitting a long time and the AUX tank looses all it's air. In this situation the Norgren valves will not operate, but with a quick dump of Marathon air, I can then adjust (lower?) suspension for fine adjustments without having to start the engine.
Note: Major raising of the suspension cannot be done this way, simply not enough pressure available from Marathon and frankly that's asking too much out of the small electric Marathon pump.

[Rickjack1216]

Thanks for the Picture. Helpful.

[Rickjack1216]

Thanks to everyone who participated in this thread on the Air compressor and different Air systems. The info has been very helpful in my Quest to Conquer the Bus systems and troubleshooting. Baby Steps in this fun knowledge journey.

[Ck2hans]

RickJack

Don't get to excited, air leaks will be a full-time job. Spent weeks getting all my air leaks stopped on Aux side, about 6,000 miles & 10 months later I am back to chasing new leaks although not as big as original leaks. On second thought, the big leaks were easier to find LOL.
Chuck