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Contaminated Air System
Won’t mention any names, but while at ETLC today, I watched Jeff check out an air system on a bus that clearly shows NO preventative maintence of the air system. It was so bad, to get the wet tank to drain, he had to poke a rod up into the drain valve to get it to open. Down stream it was just as bad, no doubt the entire air system, bags and Norgrens are in bad shape.
This was just the beginning of water and junk coming out the tank.
Solid stream of water and gunk coming from the tanks.
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7 Replies
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Yikes, that’s going to be costly……
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How old is the coach?
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I know the owner feels bad, but unless the coach is a new purchase this situation was predictable.
Let me assure all coach owners that air system inspections and maintenance recommendations are not items that would be nice to do. They are vital for the health of the coach and ignoring the air system not only is gong to cost someone a lot of money, it puts people at risk.
It is likely there will be found a lot of corrosion within the pneumatic system. Protection valves, relay valves, Norgren valves, ride height valves, ABS modulator valves, etc, etc are likely damaged and their operation is compromised. Air bags may be filled with water and it is likely if that is the case the suspension has the equivalent of smaller air bags all around which impacts handling and comfort.
The air tanks can be rusting from the inside. Brake chambers can be rusting from the inside. In short this is possibly a five figure issue that should not have ever happened.
Please service your air dryers. Please make sure you or whoever gets beneath your coach drains all the air tanks in sequence to check for moisture and the operation of check and protection valves.
Note to Prevost and other service providers: Please adopt a policy that mandates that any time a coach is up in the air and there is access to the underside all air tanks will be drained and the operation of valves will be checked. This takes less than 10 minutes and whatever it adds to an invoice will be well worth the time and cost.
Note to Prevost owners: See the above and insist on the service.
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I like just getting a puff of rust dust when you open the drains. Makes for a much cleaner system.
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Mark is not kidding about getting a puff of dust.
The air dryers on our coaches are very efficient, and if changed to a reasonable schedule the air entering the bus pneumatic system from the engine driven compressor is going to be dry.
If you are not sure of a good schedule for your air dryer service Prevost lists as one year or 100,000 miles. That is designed for commercial service so for motorhomes a best guess is all we can rely on. I change mine every two years and like Mark I get no air or oil from the wet tank where I would first expect to see moisture.
A clue the dryer needs service is if you see an oily residue around where the air dryer purges. All compressors will pass a minute amount of oil, and when this oil coats the dessicant it makes it ineffective. It not only begins to pass moisture, it shows as the residue in the area of the dryer discharge.
The moisture source mostly overlooked is going to be the aux compressor and so far it has been shown that most coaches do not have a good reliable means of trapping aux compressor moisture. This moisture enters the pneumatic system from the opposite end from the engine driven compressor so owners need to be very much aware of the need to have reliable protection on that end of the system and to service it regularly.
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My air system blows dust out when opened up also!!!!!!! After I alerted Jon about the aux air system on Liberty’s air system that the only protection from water getting in system was the spitter cup ,we then decided that people needed to add a Norgren filter before or after the spitter cup , but Jons coach had somebody disconnect the big Norgren filter on the Prevost side so he hooked it up to his aux compresser, but they all come with the Norgren filter in the steering bay on the right side coming from the aux tank for Prevost air as a last resort to get rid of moisture, I added another one on the aux compresser from liberty so no moisture ever gets in system, I change my air dryer filter every year!!!!
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Just to reinforce Peter’s post, the black Norgren water separator on the steer compartment rear bulkhead (RH side) that Prevost installs has nothing to do with the converter’s compressor unless the converter replumbed the system. While draining that doesn’t hurt, it is not draining the condensate created by the aux compressor and so far I am not impressed with whatever the converters have installed to trap water from aux air.
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