Colman Powermate 27 gal.(10 years old) Emptied all the air out of tank to remove moisture. Plugged unit back in to refill tank. While it was running started to hear a vibrating noise, thought it was hose coupling hitting side of motor. Sound got louder in a matter of seconds, ran to check and all the compressor oil was dumping and pooling on the floor from bottom of pump. What would cause this? Is pump shot? I did remove oil pan and gasket looked ok. Does the crank case build up with air pressure? Thanks.