G Man

Well, my fuel pump was leaking gas at the outlet side. I removed the copper washers and heated them to orange and let them cool down. I reinstalled them and the offending leak is gone. Is there a limit to the number of times you can soften copper that has been work hardened. I am guessing it could be done numerous times as long as the material is not deformed.

Dennis Wilson

Another trick is to sand the creases out of the washers so they will reseat/seal.

Dennis

BrianG

Heating anneals the metal and allows it to reseat. It also oxidizes some of the surface metal, which will be lost to abrasion with the friction and clamping force of the fastener. As long as there is sufficient material to maintain the structrural integrity of the "washer", it is fine to re-use.

Re-use without annealing results in "work hardening" of the material, along the lines of peening. Copper resists work hardening, compared to other metals, but it will eventually become hard enough that it won't seal well, or even crack.

Bill Ball

Ah, that helps to explain why I've seen fractured timing belt tensioner washers, which appear to be largely copper. I didn't know copper could work harden to that extent.