How to unseize a brake caliper

Seized brakes are often caused by a sticking brake caliper. If you’ve noticed your brakes have become less responsive, it’s essential to get them repaired immediately. With the right tools, it’s possible for a home mechanic to diagnose and fix the problem. Here's our guide on how to how to unseize a brake caliper.

When brake calipers sieze, the brake pads remain in contact with the disc while driving, even when the brakes are not being applied. The friction generated can impact your car's speed, handling, efficiency and performance.

Brake calipers can seize up for several reasons, including a lack of use, corrosion caused by exposure to moisture and the build-up of dirt and debris. The pistons inside your brake caliper generally seize when the dust seals have failed, allowing moisture and debris to enter the cylinder and corrosion to occur. Any corrosion to the piston or cylinder surface will lead to the caliper operation being compromised.

There are other elements of some brake calipers, other than the piston that can seize. Many modern calipers work using a sole piston, where the caliper pulls from one side to the other as the piston acts upon it. The area where the caliper slides can be prone to corrosion, leading to seizure.

All issues can simply be caused by general wear and tear from a life on the road.

Some of the signs your brake caliper has seized include a burning smell when you're driving, a car that seems to pull in one direction or brakes that feel less effective than before. You may also find that your car doesn't coast as well as it used to do.

All these warning signs suggest a problem with your brakes that needs some attention. Thankfully, diagnosing a seized brake caliper and fixing it are relatively straightforward tasks for the home mechanic.

• Locking wheel nut
• Wrench
• Lubricant
• Gloves
• Penetrating fluid
• Replacement parts like brake pads (if required)

Here’s our step-by-step guide to unseizing a brake caliper, diagnosing the problem and putting it right.

Start by removing the wheel and inspecting the caliper. To do this, you’ll have to raise the car safely from the floor using your jack. (Always use wheel chocs and axle stands.)

Once the wheel is removed you can look at the brake assembly. You want to identify the cause of the seizure to fix it (and avoid it happening again in the future). Check over the caliper, brake pads and pistons. You will need to identify whether it is the piston(s) that has seized or the sliding mechanism, depending on the type of caliper.

If the caliper and pistons are the problem, you’ll need to unseize them. Pumping the brake pedal several times may generate enough hydraulic pressure to free the seized caliper piston. Take care though, as if the piston is pushed out too far, fluid will be lost, and the brakes will need to be bled. The use of a caliper wind back tool, or a large set of grips can also help you to release the piston. Once free, you will need to inspect the piston and cylinder for corrosion. Any signs of corrosion here will require replacement or specialist reconditioning of the caliper.

If the caliper slides are seized, then remove the corrosion with a suitable tool, such as wire brush and apply penetrating fluid. Carefully apply enough pressure to release the slides until they are moving freely. Be sure to apply a grease that is suitable for braking components such as Ceratec.

If the seizure was caused by a worn, damaged, or corroded piston or sliding mechanism, you should repair or replace the caliper.

Repairing a caliper is something an experienced home mechanic can potentially do with a suitable repair kit consisting of replacement seals and dust covers, however we recommend it should only be attempted by an experienced mechanic. For peace of mind and driving safety, we recommend that you replace the seized calliper. Check the condition of the caliper on the opposite side and consider its replacement based on its age and mileage.

You can find replacement brake calipers for your car at Halfords. Enter your registration plate and you’ll see the right parts for your vehicle.

If the seizure led to the brake pads sticking to the brake disc, then replace them. Follow the steps in our guide on how to change brake pads. Be sure to replace the brake pads on both sides of your vehicle (front or rear) at the same time ensure even braking. Always apply a little brake system grease such as Ceratec to the edges of the pads that come into contact with the caliper.

While replacing or refitting the pads, check the brake disc for any scoring or damage, as you may need to replace them at the same time. Brake discs are always replaced in pairs.

For the first 100 miles, be gentle on the brakes and (if possible) avoid heavy braking.

Whether you repair or replace the brake calliper, it’s important to test the system once it’s been fitted. Take your car for a short journey and test the brakes to ensure they’re operating effectively.

Once your brake system is unseized, safe, and ready for the roads it’s important to take a few steps to ensure it doesn’t happen again.

The brake fluid in your car should be flushed every couple of years to avoid moisture building up in the fluid and damaging the caliper. You should also check the condition of your brake pads and brake discs and replace them when needed.

If you’re leaving your car for long periods, it’s a good idea to regularly move it a short distance to ensure the calipers or handbrake don’t seize up.

Worried about the cost and hassle of looking after your brakes? Halfords Brakes4Life scheme is a cost-effective way to ensure your brakes are operating safely and smoothly. Buy a set of brake pads or shoes at Halfords and we'll supply and fit all future brake pads and shoes for free – whenever you need them.

Start today by booking a free brake check at Halfords.