annealing copper crush washers fixed my brake leak

[cell]

so I have been doing a complete brake overhaul, which includes replacing my wheel cylinders.

after replacing the wheel cylinder and brake hose on one wheel, I had a small leak right where the brake hose meets the surface of the wheel cylinder.



after taking it all apart again, I noticed that the surface of the wheel cylinder wasn't completely flat. in fact it was easy to tell with the naked eye that it was not flat.



after filing it down to get a nice even, flat mating surface, I reassembled and found I still had the brake leak. it was slightly improved, but it still leaked very slowly when I depressed the brake pedal.




then I started reading about how copper work-hardens -- it gets stiffer and more brittle as you bend it, roll it, etc. I also read about how you can anneal it (rearrange the crystalline structure of the metal to make it more malleable) by heating it until it glows red for a short while and then cooling it.

so I decided to experiment with this. I went to harbor freight and bought their assortment of 100 copper washers for $8.




it occurred to me that copper washers are punched from a sheet by a press, and that sheet was created by rolling a copper ingot. both of those steps should work-harden copper, so I had a hunch that perhaps the copper washers as I bought them were already hardened, and that I might have better luck getting a good seal on my brakes if I annealed the washers before crushing them.

so I took a torch and heated a selection of washers until they glowed red, and held them at that state for about 20 or 30 seconds, then cooled them with water. I then carefully bent the annealed washers using two pair of pliers, paying close attention to how much force it took to bend them. I then bent some of the washers which I hadn't annealed, and my assumption was correct -- they were more difficult to bend, because they were hardened.




after installing my annealed copper crush washer my leak was gone!

YAY SCIENCE!

here are the above pictures in higher resolution:
http://cell.dreamhosters.com/photos/...crush-washers/