Wailing compressor

[seber]

I have a very old Quincy compressor pump that I've repurposed from gas engine to electric. It is a vertical twin with disc valves. Lately it has developed a strange noise. When I turn it over slowly it makes a very loud wailing sound. When it runs it starts out quiet and builds to a whine as the pressure builds. The whine continues for a second after the motor stops so I know it is air related. Anyone have any guesses what would cause this? Single stage with pressure relief valve

 

[marinusdees]

I have a very old Quincy compressor pump that I've repurposed from gas engine to electric. It is a vertical twin with disc valves. Lately it has developed a strange noise. When I turn it over slowly it makes a very loud wailing sound. When it runs it starts out quiet and builds to a whine as the pressure builds. The whine continues for a second after the motor stops so I know it is air related. Anyone have any guesses what would cause this? Single stage with pressure relief valve

Air leak somewhere.

 

[BreeStephany]

Is there an excess of air / oil coming out of the crankcase breather? Is the tank holding pressure? Any excess air / oil leaking from the head? Sounds more than likely to be an pin hole leak on the valves, but it could be elsewhere. Further symptoms, if any, would be very helpful.

 

[seber]

Is there an excess of air / oil coming out of the crankcase breather? Is the tank holding pressure? Any excess air / oil leaking from the head? Sounds more than likely to be an pin hole leak on the valves, but it could be elsewhere. Further symptoms, if any, would be very helpful.

I removed the valves and turned over by hand. Same wailing. Tank has always held pressure for most of a day. bleeds out overnight. Always has. Crankcase breather is dry.