Checking the caliper piston and replacing the piston protective ring (Fiesta 4)

If the protective ring is damaged or installed carelessly, dirt and moisture will penetrate into the caliper cylinder. In this case, it is necessary to replace the ring as soon as possible, otherwise the piston may jam due to dirt and corrosion, which will lead to increased wear of the brake pads and disc and uneven braking.



SEQUENCE OF WORKS

1. Remove the brake pads as described above.

2. Check whether the brake pads move easily in their guides. If not, polish the guides until they shine, being careful not to damage or displace the piston protective ring. Before installing the brake pads, apply a little consistent grease (copper paste) to the mating surfaces.

3. Check the smooth movement of the brake calipers and lubricate them with copper paste if necessary.

Checking the caliper piston

1. To check if the piston moves easily, place a clamp with a wooden block inserted into it as brake shoes for the piston so that the piston does not extend too far. Naturally, the caliper on the second wheel should be installed in the normal working position.



2. Have the assistant gently press the brake pedal. Check if the piston moves easily. If the piston does not move out, press the brake pedal until the piston starts to move. Use a clamp to press the piston into the caliper cylinder. Repeat this operation until the piston starts to move easily. Lubricate the side surfaces of the piston with brake fluid.

WARNING

If you are unable to restore piston mobility, stop working and send the caliper for repair.

Replacing the piston protective ring

1. Using a bent wire or a small bent screwdriver, remove the protective ring from the brake caliper and sliding piston. Try not to scratch the working surfaces of the sliding piston and cylinder. At the same time, watch for brake fluid leaking from the cylinder. Just in case, it is better to take the brake caliper to a car repair shop.

2. Clean the sealing surfaces with alcohol or clean brake fluid. Before you install the new protective ring, lubricate the cleaned surfaces with a preservative.

3. Carefully install the new protective ring onto the sealing surfaces. Make sure the protective ring is firmly in place.

4. Press the piston back into the cylinder until it stops.

5. Install the brake pads.

6. After finishing the work, check the brake fluid level and the tightness of the hydraulic drive of the brake system.