I am having trouble sealing the banjo fittings on the supply line to the filter housing in the engine compartment. I am using copper washers and they just arent doing it. Would aluminum work better or am I missing something? the bolt head really digs into the washer so if I try to loosen and reposition the bolt and washer, it will never seal again. I took the fitting out and used a wetstone to true it up a little. Any ideas would be appreciated.