I'm a bit worried about my front brake calipers on my MX5 MK1. I was replacing the front brake pads, and I had to push the caliper piston back in order to fit with the new pads. I used a C clamp to gently push the piston back, but after a few mm going back, it started leaking fluid.

Additionally, when I removed one of the pads, it was worn unequally, from left to right. Thinking about this, I remember that when I installed the old pads a few years ago, one of the calipers was struggling to get in, and the piston was grinding a bit on the back of the pad as I was pushing the caliper to close.

Is this an indication of a failing caliper or I should not worry and it is quite normal?

Thank you...

  • 1
    Was the piston damaged / rusty before you pushed it back in? If so then you may have damaged the seal - replace it.
    – Solar Mike
    Jan 24, 2020 at 17:49
  • @SolarMike the piston had some faint traces of rust, but nothing major.
    – Alimba
    Jan 24, 2020 at 18:02
  • Your “faint traces” can be enough to damage the seal...
    – Solar Mike
    Jan 24, 2020 at 18:24
  • 3
    Rebuild or replace the caliper.
    – Moab
    Jan 24, 2020 at 19:51
  • 1
    I always open the bleed nipples before I push the pistons back, and discard the fluid that exits
    – Caius Jard
    Mar 25, 2020 at 15:27

2 Answers 2


If your caliper has any brake fluid coming out of it, it's time to rebuild/replace the caliper. There should be absolutely no fluid loss anywhere in your braking system. If it is leaking at the caliper, not only is the caliper failing, but if the brake fluid gets on the rotor/pads, it won't provide much in the way of stopping, either. This is a huge safety risk for not only you, but anyone who might be riding in your vehicle, and anyone who might be in the way of the vehicle you are unable to stop in time to prevent an accident. Just as @Moab states in the comments, rebuild or replace the caliper. If it's leaking, it's not good.


The brake calipers is a simple hydraulic pistons system, with the rubber rings. Replace the rubber seals it will do your job. Also check for any leaks from bleeder screws.

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