When i replaced the calipers on my Jeep ZJ i had to reuse the old copperwashers. The ones that came with the caliper were simply to thin so when i put the banjo and screw in the caliper and tightened as much as i could it still leaked, the banjo bottomed out on the caliper.... But every time i have to reuse any copperwashers i always use a propane heater to heat them up glowing red and then let them cool down. That way they get soft again and might seal properly one last time. Its been 3 ears since then and i have no leaks at the calipers.