My compressor pump leaks oil

I own a Sanborn B500BPL60V-SWC upright. Oil is leaking from the pump on the side of the pump near the top on the discharge side of the pump. There is a small boss cast into the pump with a 3/16 inch? hole drilled into it. It's not a large amount of oil however there wasn't a leak before. Thanks!

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Bill says...

If oil is leaking out now, then it's possibly wicking by the piston seals.

I have no idea why you would have a hole in the side of the pump housing unless it's there to vent the sump.

That being the case, have you added oil recently? If you have, and added too much, that might be the issue.

Bill