Hi all.lve been on this site about 12 months ago with this problem and now it's back again.original mechanical seal lasted 90000ks,l replaced seal and coolant.(HP Honda motorcycle coolant) this seal lasted 17000ks.changed everything including impeller and now18000ks we have a drop of green coolant from telltale hole.(no where else) played around with air cooled engines doing rebuilds for 40 yrs and this one has got me by the balls.I have seen many comments about using lube on the seal for initial start up.l have tried both!.l have seen also different ideas on how far the impeller gets pressed into the bearing.some say 23.5mm and some say right down to the shoulder on the impeller.Have tried both!.Can any body shed some light on this for me .Please thanks Brian