Thank you guys for your replies. I was beginning to think nobody was out there. So from the threads posted until this date I've come to the conclusion that the oil filter is the cause of this problem:
When I changed the oil I did not see the white disk that is supposed to be there. That is the first thing I am going to check, along with the seals.
Also, It seems to drain very slowly which leads me to believe that the check valve is OK.
Be back soon, hopefully with good results.