Air dryer venting oil

[Keith Knight]

Just noticed trace amounts of oil venting off the air dryer exhaust port. I have upgraded the drier to the newer style with the replaceable cartridge. Is this normal or am I seeing a potential problem?

 

[Ronmar]

Where is your air feed from? Is the air feed between manifold or air filter, and the compressor clear and unkinked/distorted? restrictions there can cause excessive vacuum while operating and pull more oil past the rings… a little oil is normal, but if you have more than the normal leakage, the dryer could be working overtime. How often does your dryer purge?

 

[Keith Knight]

Not sure where the air feed is from. It’s all still original 2003 3126 m1078. All the lines are clear and no kinks. I’ll pay attention to how often it purges. How often is normal?

 

[Ronmar]

Not sure where the air feed is from. It’s all still original 2003 3126 m1078. All the lines are clear and no kinks. I’ll pay attention to how often it purges. How often is normal?

It should be a factor of how often you use the brakes. If you start the truck, it should fill and purge once, the not again until you use the brakes enough to drop the wet tank pressure low enough to engage the compressor(thats where it senses pressure).

how long does your truck hold air when setting?

the reason I asked air source, is I believe the later trucks took their air off the manifold, post turbocharger. When this is done, the dryer needs the appropriate type purge valve to halt any turbo pressure from passing on thru the compressor and dryer when the compressor is off-line…

 

[GeneralDisorder]

Should be feeding air from the charge pipe / manifold so the compressor gets the advantage of turbocharger boost pressure on it's inlet - turbocharger acts as a first stage air compressor and the piston compressor benefits from intercooled charge air......

Some small amount of oil is normal operation - it's not an "oil free" compressor so it's going to naturally put some oil in the discharge air. How much is too much is the question - a rapid increase in oil volume could indicate a problem with pistons or rings.

If you haven't, it's worth the trouble to remove the air compressor cylinder head and inspect it - mostly because these compressors like to eat exhaust valve springs and send pieces of them downstream to the dryer. But you can also look at cylinder wall condition and see if one cylinder appears to be passing more oil than the other, etc. The compressor can be rebuilt of course with new rings and a proper hone - they are quite simple machines really. The biggest issue being the valves and springs but they are easy to service and it's easy to carry a spare loaded head.

 

[Keith Knight]

Thanks for all the information. It’s very little oil. We are out on another long 5 month road trip through central US. I try only using the brakes when necessary and letting the exhaust brake do most of the work. I’ll continue monitoring it and plan on a in depth investigation when we get back home.