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OIL IN WET TANK
Getting oil in what I believe is my wet air tank. I’m hoping a certain amount is considered normal, but I really have no idea. Probably drained an once or two at my last 10K maintenance but now (1000 miles later) I realized the drain valve on that tank was leaking slowly which probably allowed a quantity of oil to return to it’s Mother Earth. Replaced the drain valve and got a little more of what appears to be relatively pure used motor oil. Can someone enlighten me?
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5 Replies
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I’ve always considered a little oil mist as normal and every bus I’ve owned did it. I put a lanyard on my last bus so I could drain the wet tank often and everytime I pulled the lanyard, you could smell a little oil mist, but there was never any on the frame or ground. The air dryer will usually give you a good indication if you have a compressor problem, the filter gets saturated with oil and then blows oil out the purge valve everytime the compressor cycles.
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This isn’t mist but rather what appears and feels like pure used engine oil.
Found a previous thread. It also mentions saturation of the dryer cartridge. This did occur on mine at about 75K miles ( it was a florida coach with tons of water in the tanks when I acquired it at 47K) but the filter was replaced at that time and hasn’t been repaced since. I guess I’ll just replace the filter, it’s been 100K, and wait it out.
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Joel,
The engine driven compressor is not unlike a car engine in that it has a piston going up and down to compress air and it’s internals are lubricated with engine oil.
As the comprerssor builds hours on it the rings begin to wear and allow oil to pass. As long as the dryer element doesn’t get its dessicant coated with oil quickly the passing of oil is tolerable. It is when so much oil passes the rings that the dryer dessicant gets coated so it no longer functions to dry the air before it gets serviced that you begin to have problems.
As Tom points out a bit of oil in the wet tank can be considered routine. You have a problem if you see oil covering the coach frame around the dryer purge valve outlet. That means the dryer element is so coated with oil that it is now being exhausted from the dryer. That could be because the element is long overdue for replacement, or if replaced regularly, it means the compressor is passing so much oil the dryer element can no longer work effectively.
I use a 2 year dryer element replacement (usually never more than 30,000 miles) interval and even though the 2 previous coaches had about 250,000 miles on them I never saw oil around the purge valve, and I would get maybe a tablespoon of oil from the wet tank along with some water. I got no moisture beyond a slight momentary mist on tanks downstream.
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Thx guys. I have the spin-on filter; I believe I saw Meritor as the manufacturer but couldn’t see a #. Anybody know if there’s a NAPA replacement filter and #?
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Wabco S-432-923-2, Meritor R 950011
That’s what was on my 97. Likely the same spin on dryer is on yours. NAPA can cross reference either of those numbers.
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