Are you tightening them to a specified torque? if not I would check the repair manual or ask a knowledgeable mechanic... just a suggestion...
I don't have an open face torque wrench although they do exist. Typically you count the number of flats after finger tight. I've also got a limited space to swing a wrench.
However your question led me to this product;
Flaretite Seals - Clip the Drip!
Which might be worth a shot.