Please also check the scavenge system (scavenge line and scavenge pipe).

The scavenge pipe sucks up the oil that collects at the bottom of the separator. It is sucked through the scavenge line back to the compressor element (air-end).

If this system doesn't perform properly, the oil will accumulate inside the separator and will eventually flow with the compressed air out of the compressor.

Please see:http://www.air-compressor-guide.com/blog/how-the-scavenge-line-keeps-your-compressed-air-oil-free

Also, make sure you stop the machine in the correct way.

An often made mistake with portable/diesel compressors is that workers just simply press the stop button while the compressor is running full-load. This will also lead to oil coming out of the compressor. Always switch to unloaded for a minute or two before shutting down the compressor to prevent this.

For more info about this: http://www.air-compressor-guide.com/learn/compressor-types/portable-air-compressor/portable-air-compressor-operation

Good luck, let me know when you found what the problem was.

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