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Where to get the correct fittings?
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The yellow valve combines your Marathon aux air with the Prevost aux air. Moisture is the enemy of your air systems.
Marathon Aux Air (yellow valve closed) – Your aux compressor(s) provide air for the Marathon systems such as pocket doors, air toilet, gen air bags, etc. You will have an aux air tank somewhere that has a manual drain that needs drained often when your setting not driving. By leaving the yellow valve closed, you protect the Prevost aux air system from being contaminated with water.
Prevost Aux Air – (yellow valve closed) Your Prevost Aux Air comes from the engine driven compressor when the engine is running. There is an aux tank under the front of your bus and you may have an aux air gauge on the dash. It provides air for your suspension, belt bellows, seat, etc. This air is dry and should be moisture free from your air dryer.
Yellow Valve – By opening this valve, you are combining the two air systems. While driving with the valve open, you are using engine driven dry air to charge both systems which is OK. With it closed while driving the engine compressor only provides air for the Prevost systems and your Marathon aux air comes from your aux compressor. You need to leave the aux compressor on while driving (unless the yellow valve is open) to keep pocket doors, gen air bags, etc. working.
Bottom line – Prevost compressor dry air, aux compressor wet air that needs moisture drained often.
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This is the valve Truk is refering to in his above post.
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I opened the yellow valve yesterday, it has always been closed. Has this set up been altered since Marathon did the conversion and If so should I change the layout of the fittings?
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Dabank………I will yield to Tom, Al and other Marathon owners to open a discussion about the how and why your system was designed the way it was and how you need to understand and maintain it.
I admit to being concerned about your efforts to replace fittings and parts without at least knowing the basics about how and why your Marathon system works.
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Dabank, if that yellow valve has always been closed…your good. That is how Marathons are designed to work. What I’ve seen over the years…some owners have chosen to bye pass fixing an air problem by mixing the air systems. Over time left that way, open yellow valve makes things very compromised.
Truk has explained it very short and sweet;
Prevost Aux Air – (yellow valve closed) Your Prevost Aux Air comes from the engine driven compressor when the engine is running. There is an aux tank under the front of your bus and you may have an aux air gauge on the dash. It provides air for your suspension, belt bellows, seat, etc. This air is dry and should be moisture free from your air dryer.
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I don’t get the question, has the fittings been altered?
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Truk,
My question is the layout of my air lines in the my picture correct or has someone change it from how Marathon installed it when the coach was new?
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Thanks ed
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Looks the same as my 02 Marathon, but yours has some compression fittings, so someone has changed out the push in fittings which is good.
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Dabank,
Also, if you have one of these green tanks for your Marathon aux tank, get rid of it and go to aluminum, the steel tanks rust internally.
2nd picture shows rusty water when drained.
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No tanks would get rusty if moisture was kept out of them.
And if the tank does have rusty water in it the water trap or dryer isn’t working.
Aluminum rusts. It rusts fast because it reacts quickly in the presence of oxygen and moisture. Only difference is it is white corrosion and not a brown corrosion.
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Wrong in saying aluminum rust fast… put both steel and aluminum in a common environment and see what goes first.
Liberty owners give aluminum a bad rap because their big waste tank leaks.
I’ll compare a accessory air tank in steel to aluminum if you would like… It certainly is not just the color of the corrosion.
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It’s impossible to keep water out of the Marathon aux air tank, aluminum is the answer.
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Les, I make the comment driven by two things. First it relates to unfinished aluminum, and most of what we come in contact with has had some surface treatment such as anodizing.
Out coaches have some aluminum parts, and I am thinking specifically of things like the boxed awnings like my Zip Dee. The end caps are almost eaten away despite having had a painted surface. When the paint bubbles and lifts off there is literally white corrosion and most of the aluminum eaten away.
Raw aluminum, like the inside of a tank does corrode. The inside of Norgrens corrode. Any moisture that is not at a ph of 7 is going to accelerate aluminum corrosion.
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I’ve obviously been educated well beyond my intelligence so I’ll defer to your empirical knowledge.
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