Originally Posted by Brian Carlton

Excellent photo and it exhibits my theory quite well.

Take a close look at the seating surface. See the annular rings that are imbedded in the aluminum? These rings are from the crush washer. The rings are designed to flatten out a bit and seal on the flat aluminum face. However, with massive torque, they dig into the aluminum, as you can see here. So, when you take a new crush washer, you are attempting for it to function on a grooved aluminum surface. This is very difficult for it to do.

For proper function, without a lot of torque, the grooves need to be carefully eliminated from this surface with a stone.

Then, a brand new crush washer should be utilized.

Finally, the torque should not be so heavy that the copper rings on the washer damage the aluminum by imbedding the grooves into it. The seal should be easy to make if the aluminum is flat.