What happens when a brake caliper goes bad?

A brake caliper is a crucial component of your vehicle’s braking system. It squeezes the brake pads against the surface of the brake rotor to slow or stop your vehicle when you press the brake pedal. If a brake caliper goes bad, it can have serious consequences for your ability to brake safely.

What is a brake caliper?

The brake caliper is the mechanism that squeezes the brake pads against the rotor when you apply the brakes. Here’s a quick overview of how calipers work:

• Calipers contain a cylinder filled with brake fluid. When you press the brake pedal, it activates the master cylinder which builds up hydraulic pressure in the brake lines.
• This pressure is transferred to the caliper, forcing the brake piston outwards against the brake pads.
• The outward force clamps the pads against the rotor, creating friction that slows the rotation of the wheels.
• Brake calipers slide along guide pins or bolts that allow them to move in and out to press the pads against the rotor.
• Once you release the brake pedal, the piston and pads retract from the rotor surface.

Vehicles typically have one, two or four calipers depending on whether they have front or rear disc brakes. Calipers are often made from cast iron or aluminum and contain high-temperature rubber seals and piston boots.

Signs of a failing brake caliper

A failing or faulty brake caliper will usually produce some noticeable symptoms that alert you to a problem:

• Noise: You may hear odd noises or grinding when applying the brakes as the caliper piston or brake pads shift unevenly. Squeaking or squealing noises can indicate issues with brake pad wear.
• Vibration: A sticking or sluggish caliper can cause uneven braking forces between wheels, creating a vibration or shaking feeling in the steering wheel, brake pedal or entire vehicle when braking.
• Pulling: Brake pull or uneven braking effort can happen if a caliper is not sliding properly or becomes frozen. The vehicle will pull to one side when the brakes are applied.
• Difficulty stopping: Braking distances are increased and stopping requires more brake pedal effort. This often indicates a caliper or piston is sticking and not applying even pressure to the brake pads.
• Overheating: A stuck caliper and dragging brake pad can overheat the rotor, brake fluid or caliper. Signs include brake fade, burnt smell or smoke coming from the wheel area.
• Leaking fluid: A damaged caliper seal or piston boot may leak brake fluid onto the wheel, undercarriage or ground.
• Uneven pad wear: Excessive or uneven brake pad wear on one side indicates an issue with that caliper’s piston or slide function.

Causes of a bad brake caliper

There are several common reasons why a brake caliper may fail or go bad:

• Caliper piston seizing: Internal corrosion, debris or moisture contamination can cause the caliper piston to stick and stop sliding smoothly. This prevents equal pad pressure.
• Caliper slide pins sticking: Rust, corrosion and dirt on the guide bolts can bind the caliper slides and pin movement. The caliper needs to be able to move to center itself over the rotor.
• Rubber seals leaking: Hardened, cracked or damaged rubber seals around the piston and brake fluid reservoir allow fluid leakage.
• Piston boot torn: A cracked or torn protective piston boot lets contaminants into the piston chamber causing it to stick.
• Damaged brake hoses: Worn, cracked or swollen brake hoses can restrict hydraulic pressure reaching the caliper.
• Lack of lubrication: Dry, dirty or corroded caliper slide pins and guide bolts inhibit proper caliper movement and function.
• Pad issues: Improperly installed pads, overheating or worn pads can all contribute to uneven pad wear, dragging and noise.
• Excessive rotor runout: A warped or uneven rotor surface forces the pads unevenly against the rotor contributing to pulling and uneven wear.

If any of these defects are present in the brake caliper, it will not be able to apply the pads evenly and create the necessary friction against the rotor to stop the vehicle. This will compromise braking performance and safety.

Dangers of driving with a bad brake caliper

Continuing to drive with a malfunctioning brake caliper is extremely unsafe and can create hazardous situations. Some of the major risks include:

• Greatly increased stopping distances that raise the chance of a crash.
• Pulling to one side when braking as the pads unevenly contact the rotor.
• Complete loss of braking capability if the caliper seizes entirely.
• Overheating of the brake components, fluid and tires from dragging.
• The possibility of brake failure if the pads wear down completely.
• Damage to rotors, pads and other brake components from uneven wear.

In extreme cases, driving on a severely malfunctioning caliper can lead to a wheel fire if the brakes overheat or complete brake failure with no ability to stop the vehicle. Do not drive in these hazardous conditions and have your brakes inspected immediately.

How to inspect brake calipers

It’s important to periodically inspect your brake calipers for signs of issues. Here are some steps for inspecting brake caliper function and wear:

1. Check for any brake fluid leaks near the wheels and undercarriage from torn caliper seals.
2. Inspect the brake pads for uneven wear. Excessive wear on one pad indicates a caliper malfunction.
3. Check for overheating signs like discoloration or cracks on the pads, rotors and calipers.
4. Examine the caliper slides and pins for smooth movement without binding or sticking.
5. Press the brake pedal firmly and check that the caliper presses the pads evenly against the rotor.
6. Measure the thickness of the brake pads. They should be replaced if under 3/16 inch.
7. Have an assistant press the brakes while you listen and feel for any odd vibrations, noises or pulling.

Any issues found during inspection require further diagnosis and repair by a qualified brake technician. Waiting can allow damage to accelerate.

How to test a brake caliper

If you suspect an issue with a brake caliper, some common tests can help confirm diagnostics:

• Visual inspection: Check for leaking fluid, uneven pad wear, damaged hardware, sticking slides, etc.
• Slide pin movement test: Try to move the caliper back and forth on its slide pins. Sticking or binding indicates a problem.
• Brake pedal test: Press the pedal firmly with the vehicle stopped. Uneven pad wear and caliper issues will be evident by noises, vibration, pulling or altered pedal feel.
• Pad drag test: Spin the wheel and check that the pads and caliper fully retract and do not contact the rotor. Dragging indicates a seized piston.
• Compressor test: Use compressed air to check piston and seal function. The piston should move out and retract smoothly without air leaks.

A full brake inspection at a shop often includes additional diagnostics like measuring caliper piston movement and brake pedal pressure to check hydraulic operation. This can help pinpoint the root cause of any caliper failures.

Brake caliper repair and replacement

Repairing or replacing a malfunctioning brake caliper is essential for restoring safe braking performance. Here are some key steps:

• Identify cause – Diagnose the specific issue causing caliper failure such as a stuck piston, bad seals, etc. This determines the needed fix.
• Rebuild or replace – Severely damaged calipers may need replacement. Minor issues can be repaired by rebuilding with new seals, boots and hardware.
• Clean and lubricate – The caliper bracket and guide pins should be thoroughly cleaned and lubricated to prevent sticking.
• Check pads and rotors – Worn pads and rotors must also be replaced to ensure proper caliper function.
• Bleed brakes – Finally, bleed the brakes to remove any air introduced during the repair process.

A professional brake shop has the expertise to properly diagnose issues and service the calipers. DIY repairs require significant mechanical skill. The brake system is safety critical and must be working properly.

Brake caliper replacement cost

The cost to replace a brake caliper can vary quite a bit depending on the make and model of vehicle as well as how many calipers require replacement. Here are some estimates on brake caliper replacement costs:

Replacement Type	Cost (Parts + Labor)
Single front caliper	$150 – $400
Single rear caliper	$125 – $350
All four calipers	$600 – $1,200
Remanufactured calipers	$50 – $150 per caliper

Labor costs make up a significant portion of this, often $100 per hour or more. Higher end vehicle models also have more expensive caliper components. Replacing just the failed part may appear cheaper initially but compromises system integrity versus replacing in axle sets.

Preventing brake caliper failure

You can help minimize brake caliper problems by following proper maintenance practices:

• Check brake fluid level and condition regularly. Flush fluid every 2-3 years.
• Inspect brake pads frequently. Replace them promptly when worn.
• Lubricate caliper slides, pins and bolts when servicing brakes.
• Never drive on worn pads or rotors.
• Resolve any issues with pads dragging, sticking or uneven wear immediately.
• Listen for noises or vibration when braking as early signs of issues.
• Confirm hardware like slides and hoses are in good condition.

Following the vehicle manufacturer’s brake and caliper service recommendations helps prevent premature wear and failures leading to expensive repairs.

Conclusion

A malfunctioning brake caliper is extremely dangerous and will seriously compromise your ability to stop safely. Warning signs like pulling, vibration, uneven pad wear and noise indicate a problem. Sticking pistons, seal leaks and hardware damage are common causes. Have any issues diagnosed and repaired immediately before severe damage or a crash occurs. With proper preventive maintenance and timely service, brake calipers can provide reliable, smooth and safe operation for tens of thousands of miles.