News

How to Replace a Brake Caliper (Including Bleeding the System)

Replacing a brake caliper is mechanically straightforward. What makes it different from other jobs is that you are opening the hydraulic system, which means bleeding afterwards is mandatory, and the consequences of doing it badly are serious. Take it seriously and it is a manageable afternoon. If you are not confident working on brakes, this is a reasonable job to hand to a shop. There is no shame in that judgement. Before You Start Tools: socket and spanner set, including a flare nut spanner for the brake line fitting. A regular open-end spanner rounds those fittings easily. Also: torque wrench, jack and axle stands, C-clamp or piston tool, brake fluid, a container and clear tubing for bleeding, brake cleaner, and silicone-based brake grease. Buy the right brake fluid. Check the specification on your reservoir cap. Do not mix types, and use fluid from a sealed container — brake fluid absorbs moisture from the air, and an opened bottle that has been sitting is already compromised. Replace calipers in axle pairs. Uneven braking force side to side is a handling problem. Plan to replace the pads at the same time, and inspect the rotor. A caliper that was dragging has usually overheated its rotor. Step 1: Loosen and Lift Loosen the lug nuts with the vehicle on the ground. Raise it, support it on axle stands, chock the remaining wheels, and remove the wheel. Step 2: Prepare for Fluid Loss Open the brake fluid reservoir and remove some fluid if it is near full — compressing the piston later pushes fluid back up and can overflow it. Brake fluid strips paint, so protect surrounding bodywork and keep a rag handy. Place a container beneath the caliper to catch what drains when you disconnect the line. Step 3: Disconnect the Brake Line This is the step that demands the right tool. Use a flare nut spanner, which grips the fitting on more faces than an open-end spanner. Rounding a brake line fitting turns this job into a line replacement. If the fitting is seized, penetrating oil and patience. Do not force a rounded fitting further. On calipers using a banjo bolt, note the position of the copper crush washers — there is one on each side of the fitting, and they must be replaced with new ones. Reusing crush washers is a common cause of a persistent leak. Once disconnected, fluid will drain. Plug the line or clamp the flexible hose to limit loss, and keep the open end clean. Step 4: Remove the Caliper Remove the caliper mounting bolts and lift the caliper off the rotor. Remove the caliper bracket if you are replacing it or accessing the pads. Note how the pads, shims and clips are arranged before removing them. Photographing the assembly before disassembly is worth the ten seconds. Step 5: Service or Replace the Slide Pins On floating calipers, the slide pins are the most common cause of trouble and are often the actual fault rather than the caliper itself. Remove the pins and inspect them. They should be smooth and clean. Clean out the bores. Inspect the rubber boots. Torn boots let water in, which is what seizes the pins. Apply silicone-based brake grease, not petroleum-based grease. Petroleum products swell the rubber boots and cause the exact problem you are trying to prevent. The pins should slide smoothly by hand when refitted. Step 6: Fit the New Caliper Compare the new caliper against the old one before fitting — bleeder position, line fitting type and bracket design should match. Fit the bracket and torque to specification. Fit the pads with their shims and hardware in the correct orientation. Many pads have a wear indicator that goes on a specific side. Mount the caliper and torque the bolts to specification. Connect the brake line with new crush washers where applicable, and torque the fitting appropriately — firm, but these fittings do not need extreme force and can be damaged by overtightening. Step 7: Bleed the Brakes This is not optional. Air in the hydraulic system means a soft pedal and reduced braking. Basic two-person method: Top up the reservoir and keep checking it throughout — if it runs dry you introduce air into the master cylinder and have to start over. Attach clear tubing to the bleeder screw, running into a container with some fluid in the bottom. Have the helper press and hold the brake pedal. Open the bleeder, let fluid and air escape, then close it before the helper releases the pedal. Repeat until the fluid runs clear with no bubbles. Follow the bleeding sequence specified for your vehicle. Many call for starting at the corner furthest from the master cylinder, but check yours — some vehicles specify a different order. Vehicles with ABS sometimes require a scan tool to cycle the ABS module during bleeding. If the pedal remains soft after conventional bleeding, this is likely why. Step 8: Check Before Driving Pump the pedal several times until it feels firm. It should not sink toward the floor under steady pressure. Inspect every fitting you touched for leaks, with the pedal under pressure. Top up the reservoir to the correct level. Refit the wheel and torque the lug nuts in a star pattern. Step 9: The First Drive Before moving, pump the pedal to seat the pads against the rotor. Test the brakes at walking pace in a safe, empty space before entering traffic. Bed in the new pads according to their instructions — typically a series of moderate stops from moderate speed, avoiding coming to a complete stop while the brakes are hot. Check for leaks again after the first drive. Common Mistakes Using an open-end spanner on the line fitting. Rounds it, and now you need a new brake line. Reusing crush washers. Causes a slow leak that shows up days later. Petroleum grease on slide pins. Swells the boots and seizes the pins. Letting the reservoir run dry while bleeding. Introduces air into the master cylinder. Not bleeding thoroughly. A soft pedal is a safety failure, not an annoyance. Driving before testing. Always confirm pedal feel in a controlled space first. Replacing one side only. Uneven braking force pulls the vehicle under braking. Before You Order the Part Calipers are side-specific and vary by brake package — the same model can use different calipers depending on trim, engine or rotor size. Confirm front or rear, driver or passenger side, whether the bracket is included, and the brake line fitting type. Match the fitment chart to your exact year, trim and brake configuration. Order new crush washers, pads and brake fluid at the same time so you are not stopped mid-job.