Hyd oil in motor oil d41e

I have a d41 e dozer and the hyd oil is getting into the oil pan . I verify this by hyd resivor goes down and engine oil dipstick goes up. I took hyd pump off to see filled with oil it would leak . One wk later and there is no signs of leak. But I haven't tried to put under pressure, but anyways what other areas should I look at if any thanks.