I have a 20 yr old Campbell Hausfeld cast iron 20gal/4hp compressor that is bubbling oil out the crankcase breather. The oil level is correct. This unit has not been used for several years because of a bad tank, but has been run a couple of times. The problem occurred with the installation of a new tank. Tank pressure is 100 PSI which is the second problem as it should max at 120 PSI.