What causes a brake caliper to stick?
Brake calipers are one of the most important components of modern disc brake systems. They work with the brake pads and rotors, as well as the rest of the hydraulic system, to slow and stop the vehicle. When the brake pedal is depressed, brake fluid pressure is pushed through the master cylinder to the caliper, which extends the piston and forces the pads against the rotors to slow the vehicle. Over time, brake calipers are exposed to the intense heat generated during braking and can eventually fail, affecting the vehicle's stopping power and adversely affecting its handling and safety characteristics. Brake caliper problems are one of the braking issues every driver should be aware of.
What are the signs of a seized brake caliper?
The brake caliper plays a vital role in your vehicle's braking system. Unfortunately, it can wear out or even seize up. A seized caliper occurs when the piston no longer slides normally. Symptoms of a seized brake caliper include the following:
- Your car tends to pull to one side: Because the piston doesn't retract properly, a drag remains on the wheel with the seized caliper. The vehicle then begins to pull to one side, and the wheel does not move as fast as the wheel on the opposite side.
- Wheels vibrate when braking;
- Abnormal noise, especially when braking;
- Brake fluid leaks: Brake calipers require brake fluid pressure to actuate the piston. However, the piston seal wears out over time.
- A burning smell: the constant friction of the pads on the disk when the caliper piston is not retracting causes them to heat up;
- Finally, the impression that the brakes are constantly applied, which is more or less the case when the caliper is seized.
Why is my brake caliper sticking?
Common reasons a brake caliper sticks are:
- Exposure to moisture and dust. Contaminants build up and prevent the piston and guide pins from moving freely. Fluid causes them to corrode and then stick. When rubber dust boots designed to protect moving parts from an aggressive environment leak, the risk of piston and pin failure is increased. Sticking is also more likely if brake fluid is not replaced in time: it is hygroscopic, so its water content increases over time, leading to piston and pin corrosion.
- Using the wrong lubricants. Special high temperature resistant greases must be used on guide pins. Unsuitable grease tends to dry out or leak; it can also destroy rubber parts. The pin cannot move freely in a swollen ring.
- Abrupt temperature changes. These have a negative effect on rubber dust boots. They accelerate corrosion and can cause the rotor to twist, often resulting in brake sticking.
- Worn caliper components. A worn caliper housing or piston surface causes twisting and sticking. Dust accumulates in damaged areas, restricting free movement of moving parts. Air infiltration accelerates corrosion.
- Guide pins can bend due to improper installation, heavy use, or careless driving; this also increases the risk of seizure.
- Riding with worn pads and rotors. In order for a friction pair to adhere properly, the piston may come out of its seat, causing it to twist.
- Using the wrong brake fluid. If a brake fluid is too viscous, the pistons will not return to their original position. Also, polymer or composite pistons may swell upon contact with improper brake fluid.
- Exposure to aggressive chemicals. Road grit and brake fluid can cause premature wear on rubber dust boots, so it's important to keep the system sealed at all times.
How do you free your vehicle's brake caliper?
A seized brake caliper is a safety hazard for you and others. You don't want to compromise your braking system in this way. But it's perfectly possible to release or replace a caliper - in fact, it's necessary.
- Remove the caliper: Start by applying the handbrake and chocking the car for your own safety. Then remove the wheel. Next, remove the caliper. Unscrew the two screws and remove the caliper. Don't forget to remove the brake pads as well.
- Clean the parts: Soak the caliper in degreaser. Also spray the caliper slideways with degreaser and soak the piston. You may need to loosen it first: you can pump the brake pedal to loosen it.
- Reassemble the caliper: Once the parts have been cleaned with degreaser, replace the caliper seals and, if necessary, the piston bellows. Then reassemble the caliper. But that's not all! You still need to bleed the brake fluid. When the bleeding is complete, top off the brake fluid and test your brake system.
Tips to prevent caliper seizure
- Replace brake fluid on time. High moisture levels in the brake fluid cause piston corrosion.
- Check the caliper dust boots regularly to ensure they are in good condition. If they are damaged, dust will collect on the caliper pistons.
- Use brake fluid recommended by the vehicle manufacturer. Fluid that is too viscous will cause the pistons to return slowly to their original position.
- Lubricate the caliper pivot pins every six months. This will allow the moving parts of the assembly to move freely along their working paths.
- Clean the caliper. Use a brake cleaner and wire brush to remove dust.
The brake caliper is one of the most important parts of the brake system of your vehicle. Because of its essential role in the smooth operation of your vehicle, we recommend that you regularly maintain this part by cleaning it when it becomes stuck. When worn, replace your brake caliper as soon as possible: your safety on the road depends on it.