oil trap

I have an 89 240 wagon, 203000km. Engine passes through aircare tests no trouble. But in the last month I have taken off the oil trap 2 times, blasted air through it, washed it out with alcohol. And a couple of weeks later I see oil pushing past the oil filler cap again. I also blasted air though all the hoses coming off the oil trap. How come this problem keeps coming back? Am I missing something? any suggestions would be appreciated.