Caliper Piston Seal Leak
A caliper seal leak lets brake fluid escape at the caliper piston, reducing brake pressure and contaminating pads.
Can I Drive?
stop-driving
Most Likely Causes
- 1
Piston seal worn or cut
The seal can fail from age or corrosion.
- 2
Pitted piston surface
Rust damages the seal lip.
- 3
Overheated caliper
Heat hardens seals.
- 4
Incorrect caliper service
Improper piston compression can damage seals.
How to Diagnose It
- 1
Inspect inside caliper and pads
Look for wet fluid around piston boot and pads.
Tool: Wheel removal tools
- 2
Check fluid level
A caliper leak lowers reservoir level.
- 3
Verify pedal firmness
Leaks often cause a sinking or soft pedal.
Tool: Safe stationary test
How to Fix It
Replace or rebuild caliper
Use a rebuilt/new caliper or rebuild kit if appropriate.
Replace contaminated pads
Fluid-soaked pads should not be reused.
Bleed brakes
Restore hydraulic pressure after repair.
Mistakes to Avoid
- Do not wipe off a leaking caliper and keep driving.
- Do not reuse pads soaked with brake fluid.
- Do not replace only one caliper if the opposite side is also seized or leaking.