Shogunther,
The PO of your car had the same problem. In your previous post ..."look what I found" your picture showed no RMS. Here is your picture.
http://forums.pelicanparts.com/showthread.php?t=476629
Every thing looks normal. Make sure you have no burrs in the screwdriver recess area or poking up towards the crankshaft, clean the opening and crankshaft. Use liberal amounts of WD-40 or Curil-T. Oil the inside lips of the RMS with thick oil. Buy a 4" screw in sewer cap at HD-take your old seal along for measurement. Gently tap the RMS in. The KACO seal without lower ribs will start easier.
Good luck
John_AZ