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Symptoms of bad brake caliper

Symptoms of bad brake caliper — How long do they last?

What are the symptoms of a bad brake caliper?

• Brake fluid leaking on the ground
• Soft/spongy brake pedal
• Low brake fluid in reservoir
• Grinding noise when braking
• Squealing noise when braking
• Car pulls to one side when braking

What fails on a brake caliper?

Corroded caliper pins

Floating brake calipers operate by sliding on lubricated caliper pins. Rubber boots protect the slide pins by keeping water and salt out. But the rubber boots degrade over time. Then, water gets in and corrodes the caliper pins, causing the brake caliper to not release proper. And that causes rapid brake pad wear, along with a grinding noise and squealing when braking.

new versus corroded caliper slide pins

Corroded slide pins alone is not a reason to replace the entire caliper. New slide pins cost around $11/set.

Leaking caliper piston square cut O-ring seal

If the brake caliper is leaking, it must be replaced.

leaking brake caliper

Torn dust boot

The piston dust boot prevent dirt and grit from corroding the caliper piston and wearing out the square cut O-ring. Any tear in the dust boot is serious.

torn dust boot on brake caliper

Caliper square cut O-ring has hardened and doesn’t “roll-back” to release brake pressure

caliper o ring diagram

The square cut O-ring is responsible for pulling the caliper piston back into the caliper bore. When you apply the brakes, the brake fluid pressure pushes the piston forward and that forward motion twists the square cut O-ring. When you release the brakes and remove fluid pressure, the O-ring wants to return to its former shape. As it “rolls back” into its original position, it pulled the piston with it.

When the O-ring hardens over time, it loses it’s ability to twist or roll back. When that happens, the caliper piston doesn’t retract and stays in contact with pad, wearing out the pad and rotor much faster.

If the brake caliper piston isn’t retracting when you release the brakes, it must be rebuilt or replaced with a rebuilt unit.

Why brake shops replace calipers on every brake job

Many of chain operated brake shops replace brake calipers on every brake job, whether they need it or not. For example, The Les Shwab chain brags about how they replace brake calipers on every brake job.

One reason they always replace calipers is because they only buy fully loaded calipers from their vendors. In other words, they don’t buy pads alone. A fully loaded caliper comes with a rebuilt caliper, new caliper pins, pin boots, anti-rattle clips and new brake pads. So you get the whole shootin’ match whether you need it or not.

How to prevent brake caliper problems

• Always use the proper tools to compress the piston when performing a brake pad change. Never use screwdrivers or pry bars. Those can damage phenolic pistons and damage the dust seals.

• Always replace the caliper pin boots and grease the slide pins when doing a brake job. A caliper boot kits costs around $6 and keeps water out of the slide pin bores.

• Perform a brake fluid flush when recommended by the carmaker. Brake fluid anti-corrosive additives break down over time and corrosion sets in. That corrosion can settle in the brake caliper piston bores and prematurely wear out the square cut O-ring seal, causing a perfectly good caliper to leak.

©, 2021 Rick Muscoplat

Posted on by Rick Muscoplat



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