I'm struggling to diagnose and repair a leak right where the brake line feeds into the caliper.

I've replaced the copper washers, the banjo bolt, and even the caliper itself, all to no avail. I'm confident that I'm torquing the banjo bolt enough because I can see the grooves imprinted in the copper washers when I remove them.

Here are some photos to illustrate:

leak at banjo bolt

copper washers

Given that I've replaced everything except the brake line and yet the leak still persists, I'm beginning to think that the problem is perhaps caused by the brake line. But I can't see how. The mating surfaces look smooth to me.

  • Should I try somehow sanding down the brake line's mating surfaces?
  • Should I just go ahead and replace the brake line?
  • Is there something else I should check or double check to identify the cause of this leak?
  • How tight is the banjo bolt? Your tight might not be enough.
    – Moab
    Commented Aug 25, 2019 at 19:50
  • @Moab - I haven't measured with a torque wrench, but tight enough to crush the washers as shown in the picture. I've gone as hard as I can without using any extension on my wrench. Commented Aug 26, 2019 at 2:47
  • Is the locating pin on the banjo going all the way into the hole on the calliper? If something is stopping it going in, the banjo may not be seating properly.
    – HandyHowie
    Commented Aug 26, 2019 at 7:47
  • @HandyHowie - I believe it is. I've disconnected and reconnected the hose and banjo bolt, so I'm sure they're seating properly. Commented Aug 28, 2019 at 1:04

1 Answer 1


I'd replace the brake line at this point. Seems you've already wasted too much time and energy on the old one.

  • Perhaps I should have done that a while ago. I just couldn't imagine how it would help. But at this point, it seems there is nothing else to try. I'll report back. Commented Aug 28, 2019 at 1:06

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