34 21 812 Overhauling left or right rear brake caliper (brake caliper removed)

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2010 BMW X3, 2009 BMW X3, 2008 BMW X3, 2007 BMW X3, and 2006 BMW X3. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Use repair kit.

Take off plastic caps (1).

Unscrew guide screws (2).

Installation:

Only clean guide screws; do not grease. Check guide bolts, replace if necessary.

Tightening torque: 34 21 5AZ, see 34 21 REAR BRAKE .

Fig 1: Guide Screws And Plastic Caps

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Dismantle brake caliper and remove brake linings.

Installation:

Press brake lining fully outwards and insert spring (4).

Fig 2: Brake Lining Fully Outwards And Spring

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WARNING: In the following work step, large forces occur at the brake caliper piston (up to more than 2800 N!).

Danger of injury!

Carefully force piston out through connection bore with compressed air.

To protect piston, place a protective plate (e.g. hard wood or hard felt) in caliper recess.

Do not grip piston with fingers - risk of trapping!

Fig 3: Locating Brake Caliper Screw

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Check guide sleeves (5), fitting repair-kit guide sleeve if necessary.

Fig 4: Guide Sleeves

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Remove sealing ring carefully with a plastic needle.

Clean cylinder bores and parts with alcohol and dry with compressed air.

Thoroughly inspect cylinder bore, piston and flange surfaces.

Machining of cylinders and pistons is not permitted.

Fig 5: Removing Sealing Ring With Plastic Needle

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Installation:

Apply a light coat of Ate brake cylinder paste to cylinder bore, piston and sealing sleeve.

Install sealing cover in rear annular groove of cylinder bore.

Fig 6: Sealing Cover In Rear Annular Groove Of Cylinder Bore

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Insert dust sleeve in front annular groove and press into annular groove over entire diameter.

Installation:

The area between the dust sleeve and the brake caliper housing must be kept dry. This area must not come into contact with Ate brake cylinder paste or brake fluid so as to ensure that the dust sleeve is perfectly seated.

Fig 7: Area Between Dust Sleeve And Brake Caliper Housing

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Take up brake piston with a commercially available extension and socket and gently press onto dust sleeve.

Blow up sleeve with compressed air (max. 3 bar). Sleeve jumps over brake piston.

Installation:

Coat dust sleeve and brake piston with brake fluid to facilitate installation of dust sleeve.

Fig 8: Pressing Onto Dust Sleeve

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