I have a rebuild my motor , new main seal installed , but I am noticing moderated oil leak on the back of the motor , I can't figure out from where but my wheel pulley cover under the car is wet, if there a chance that valve cover can be cracked ? cuz I changed the gasket OEM , but valve cover made of some type aluminium or alloy! if there anything else on the back on the motor that can leak besides main seal and valve cover?