Removing and installing brake caliper piston: Audi A8 D4

🧭 Before you start

Remove the pads and the caliper, clamp it in a vice with jaw covers and force the piston out with compressed air against a wooden block. Lift out the seal with the wedge, clean with methylated spirits and inspect the bore. Grease and fit the new seal and protective cap, set the compressor nut, press the piston home by hand or with the resetting tool and refit the caliper and pads.

Fits: Audi A8 D4 (4H, 2010–2017)

• Opens: brake fluid

Don't miss

• Keep fingers out of the caliper when using compressed air; wear goggles and cover the bore with cloth.
• Clean parts only with methylated spirits; mineral solvents swell the rubber seals.
• Renew the caliper if the piston or the piston bore is damaged.
• Screw the compressor nut in to the stop, then back it off a quarter turn.
• Check the protective cap sits in the piston groove once the piston is pressed fully home.

Written for this job from the workshop steps below · TorqFix editorial.

📋 Procedure

1. Remove brake pads .
2. Remove brake caliper and disconnect from hydraulic system .
3. Clamp brake caliper in jaws of vice. Use protective jaw covers. [Note: Take care not to damage paint on brake caliper when removing brake caliper piston and protective cap.When removing ensure that the bore of the cylinder is not damaged.]
4. ⚠ Risk of injury.Wear safety goggles.When pressing out brake caliper piston, DO NOT reach into brake caliper with your fingers.Place a cloth over bore in brake caliper to catch any brake fluid spatter. Wrap another cloth tightly around nozzle of compressed-air gun applied to brake caliper.Always wear chemical-resistant protective gloves to prevent brake fluid from contacting skin. — Screw piston out of brake caliper as far as possible.
5. Place a piece of wood in the caliper to prevent damage to the piston when it is forced out.

6. Apply compressed air nozzle to threaded hole for brake hose and press piston out of caliper.
7. Remove seal from brake caliper using removal wedge3409. [Note: Install all parts supplied in repair kit.Use only methylated spirits to clean the brake components.The brake caliper must be replaced if a brake caliper piston or piston bore is damaged.]
8. The surfaces of the piston and seal must be cleaned only with methylated spirits and then dried.
9. Apply thin coat of lithium grease to brake caliper piston and seal Electronic parts catalogue.
10. Fit seal in brake caliper using removal wedge3409.
11. Fit protective cap onto brake piston as shown in illustration.
12. Screw compressor nut (1) clockwise into brake caliper (arrow) as far as stop and then slacken off by a quarter turn.
13. Fit protective cap into groove in brake caliper using removal wedge3409.
14. Carefully press piston into brake caliper, moving piston as required.
15. After guiding brake piston onto compressor nut, press piston into brake caliper as far as stop. [Note: Take care not to damage the compressor nut.]
16. Press piston into brake caliper by hand. [Note: You can also use piston resetting appliance T10145 to press in the brake piston.Make sure that the protective cap is located in the groove of the brake piston when the piston is pressed in all the way.]
17. Install brake caliper .
18. Install brake pads .

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