Are Oil Free Air Compressors REALLY Oil Free?

[SpikeWills69]

I have an upright 27 gal. Oil Free air compressor that was in the trailer that wrecked (another thread). When the wrecker crew cleaned everything up they laid the compressor down on the rollback and oil ran all over. They stood it up when they noticed, but where did the oil come from? I have been afraid to start it up to see if it still works because of that. What gives? All the documentation I can find says no oil. So where did it come from? Any help would be appreciated.

 

[RustyRatRod]

"Oil free" when speaking of compressors doesn't mean they don't have oil. It means they are not servicable. In other words, they are permanently sealed. If oil came out of that compressor, then either is is cracked or broken somewhere, or it was on its side a vary long time. Long enough for the oil to perhaps run out of the air intake. I am not sure you can add oil back to one of those. I generally stay away from those unless like my little portable pancake compressor for like my nail guns and such. They are great in that application, but oiless compressors much larger than that are not for any sort of heavy duty use at all. Opinions vary, but that's mine.

 

[dodgedifferent2]

There is a way to add the oil back in .... i just do not know how. I would have to look.
The oil was put in there when the compressor was built.. or installed so somebody put some in.

The only concern is where it leaked out of. If its cracked then not good.

I am thinking there should be a pipe plug with a square head or an inset allen head. It could also be a regular hex...

 

[CARS]

I just helped a friend fix an oil-free Sanborn compressor that wasn't "pumping up" like it should.

When the cover was removed you see an exposed rod going up to a "piston". All exposed, no oil.

The piston sleeve had split. The sleeve is just about as thick as a tin can (if not closer to an aluminum can).

Amazingly, it was still a serviceable part. Around $20.00 for a sleeve, rod, and piston.

So... On this one the motor is connected to the rod with an eccentric and sealed bearing. Where in the world would oil come from???

The oil-free Craftsman in my garage is the same way but has 2 pistons.

 

[cosworth]

Theres different types of "oil free" compresssors. Some are just sealed units like SS was saying and others use sleeves/teflon coatings and completely do away with oil. The sealed unit would have to come apart to the point the factory put the oil in then sealed back up but would need to know if the oil just came out of the intake/exhaust or if theres a crack.

Ive worked with several high end types for medical applications.

 

[SpikeWills69]

There is a way to add the oil back in .... i just do not know how. I would have to look.
The oil was put in there when the compressor was built.. or installed so somebody put some in.

The only concern is where it leaked out of. If its cracked then not good.

I am thinking there should be a pipe plug with a square head or an inset allen head. It could also be a regular hex...

Guys, thanks for the feedback. I couldn't see any "visible" damage to the compressor, but couldn't get the plastic shroud off w/o proper tools. Compressor is in my daughter's garage now, about 4 hrs away. Taking the right tools back with me to investigate further, next time we are up there. Just moved and we have stuff in three different places until we get settled. It is a Coleman and according to the documentation, there are a lot of parts available to repair it.

I will look for a plug. One of the diagrams online does show a plug, but not sure it is specific to my exact compressor. Need to have the cover off. Thanks again.

Jim