oil pooling in air cleaner housing

[Pilotx1]

I own a 1984 190e with 97000 original miles on it. Recently I was checking on the air filters condition and found that it was saturated with engine oil in 1 spot and there was a small amount of oil pooled in the air cleaner housing. I know that the oil is comeing in through a tube connection the housing to the valve cover. I replaced the filter but oil comes back. I was thinking about putting a peice of white breather filter into the small cup like section in the housing above the tube to catch the engine oil and stop it from getting on my airfilter. Any ideas about this good or bad? Also should I be worried about the oil getting into the air cleaner housing ? what could be causing this?