I really don't know how I developed a leak. In fact It wasn't convinced that I really had a leak as I couldn't see any obvious problem. I just found that I had very poor performance and lots of noise.wookieone said:No Seals for shimano brakes, it leaks, get a new one, BS if you ask me. How did you develope a leak? I did it riding in the cold, a no no, I am told. Curious how many folks have had this issue.