Hayes Nine Brake Leak
Went to bleed Hayes Nine brakes. After I was finished, the master cylinder began leaking from a small hole located beneath the bleeding port. This hole is also located on the other master cylinder. I did not bleed that brake and no leaking is occurring. Anybody have an idea why this is happening or why the hole is there?
That pin hole equalizes the pressure in the reservoir when the bladder expands or contracts. Unfortunately, as you discovered, it also allows fluid to leak out if the bladder leaks. While Hayes no longer produces replacements for some models (Hayes Nine) and few are available from shops, I found a simple solution for my leak that was caused by the bladder separating from the bleed port..
1) Loosen the torx bolt and turn the brake lever/reservoir around, so the reservoir cap points up.
2) Remove the 2 small torx bolts holding the cap and remove the cap.
3) Fill the bladder if it's not full.
4) Cut a 1" x 2" piece of rubber from an old inner tube (the thinner the better) and clean it of any dirt/powder.
5) Place this patch on the cap, use a pin or nail to punch holes for the bolts, and put it back on the reservoir.
While the pin hole will continue to be able to equalize the pressure, it will no longer be possible to use the bleed port when bleeding the brake. To solve this problem, simply loosen the cap when adding fluid at the caliper until the fluid starts to seep out around the patch. This repair will take you 15 minutes, cost nothing, and solve the leaking problem. Good luck