I've had an annoying oil leak from around the drain plug for what seems like forever. I've always used new crush washers and recently, even used a new drain plug and new crush washer. Still the leak. Makes a mess on the garage floor (unless I put some paper towels under it) and eventually gets on the brake switch, pipes, etc.
I pulled the tank and below is how the drain looks. After 40 years, it's scored (see pic below), but I would have thought a crush washer would still handle this. Not so. I plugged the holes for the oil hoses, installed a new washer and the plug and filled the tank with water. Sure enough, water begins to seep/drip around the drain and washer. I tried to pinpoint where the leak was located by 'carboning up' a washer in candle flame, but the carbon didn't transfer well to the drain opening.
I thought about trying to find a oil resistant rubber washer to conform better, but I'm concerned that over time with the pressure of the bolt and heating/cooling it might not retain the necessary tension on the bolt. Another thought was some sort of fiber washer.
I guess the best solution might be to redress the end of the drain. Any ideas on how best to to this? I'm considering a wet stone or fine file, but am a little concerned about keeping it square to the rim, etc. Any suggestions would be appreciated.