After about 700 hours, my 912uls is starting to leak coolant from the weep hole below the water pump more than I would like. For a while it has just been a little leakage that was not noticeable in the coolant level. Now it is enough that I have to add about 1 cup or so to the overflow bottle in between 50 hour oil changes. My question is: has anyone replaced the water pump seal and what kind of a job is it? Special tools required? Does engine need to be removed?