Replacement

Four Piston Fixed Caliper:

Checking
1. Check lining thickness of brake pads and 11 the brake pads have worn beyond the AP42.10-P-4251BA condition of brake discs. permissible wear limit, the land between the sealing groove and dust cap may be damaged, therefore, check brake system for leaks using pressure tester, refer to Leak Test. Testing and Inspection

Removal

DANGER:
^ Risk of poisoning due to consuming brake fluid.
^ Risk of injury due to brake fluid coming into contact with the skin and eyes.
^ Only pour brake fluid into suitable appropriately marked containers.
^ Wear protective clothing and safety glasses when handling brake fluid.

NOTE:
^ Refer to Notes On Brake Fluid.
^ Refer to Notes on Test and Repair Work to brake system.

2. To prevent the brake fluid reservoir overflowing when the piston is pushed back, if necessary, extract some brake fluid from the brake fluid reservoir.
3. If fitted, pull front brake pad wear sensor (S10/1) out of the connector (52).
- Refer to notes on installing brake pad wear sensors. Service and Repair
4. Drive out retaining pin(s) (41) using a punch (035).
5. Pull out brake pads (43) with release lever (034).
6. Pull front brake pad wear sensor (S10/1) out of lining back plate or brake pad.
- Refer to notes on installing brake pad wear sensors. Service and Repair
7. Press back piston (47) with resetting device (031).
- Secure an opposed pair of pistons with plastic wedges to prevent them sliding out.
- Press back the other pistons using the resetting device, not bending the heat shield.
- If the piston is difficult to move, repair front axle fixed caliper, refer to Overhaul. Service and Repair
8. Clean brake pad guide using a brake caliper brush (030).

Installation
9. Install in reverse order.
- Install brake pads (43) with peripheral damper (a and c) dry.
- Smear the side surfaces (arrows) of brake pads (43) without peripheral damper lightly with brake pad paste.
- Only sets of brake pads approved by Mercedes-Benz must be installed.
- Brake pads must be disposed of as hazardous waste.
- Local authorities can provide information as to whether the brake pads may also be disposed of as industrial waste similar to domestic waste.
- Drive in retaining pin(s) up to the stop using a drift punch.
- Replace defective wear sensors

DANGER:
^ Risk of accident, when commissioning the vehicle due to a lack of braking effect when the service brake is operated for the first time after repair work.
^ Before commissioning the vehicle, operate the brake pedal several times until the pressure in the brake system is built up and maintained.

10. Operate the brake pedal several times until the brake pads contact the brake discs (firm resistance detectable).
11. Check brake fluid in brake fluid reservoir and correct if necessary.
- Top up or extract brake fluid up to the max. mark on brake fluid reservoir.

NOTE:
^ Refer to Notes On Brake Fluid.
^ Refer to Notes on Test and Repair Work to brake system.