12 31 020 Removing And Installing Or Replacing Alternator (N51, N52, N52K, N53)

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2013 BMW 128i, 2012 BMW 128i, 2011 BMW 128i, 2010 BMW 128i, and 2009 BMW 128i. However, it is still accessible from the selected car via links, so may be relevant.

IMPORTANT:

Aluminum-magnesium materials .

No steel screws/bolts may be used due to the threat of electrochemical corrosion.

A magnesium crankcase requires aluminum screws/bolts exclusively.

Aluminum screws/bolts must be replaced each time they are released .

Aluminum screws/bolts are permitted with and without color coding (blue).

For reliable identification:

Aluminum screws/bolts are not magnetic .

Jointing torque and angle of rotation must be observed without fail (risk of damage) .

Necessary preliminary tasks:

Switch off ignition
Disconnect battery negative lead . See 61 20 900 DISCONNECTING AND CONNECTING BATTERY NEGATIVE LEAD (CONVERTIBLE) or 61 20 900 DISCONNECTING AND CONNECTING BATTERY NEGATIVE LEAD (COUPE) .
Remove intake filter housing . See 13 71 000 REMOVING AND INSTALLING/REPLACING INTAKE FILTER HOUSING (N51) .
Remove alternator drive belt

Unlock plug (1) and remove.

Slacken nut (2).

Installation:

Tightening torque, see 12 31 1AZ in 12 31 ALTERNATOR WITH DRIVE AND MOUNTING PARTS .

Release screws and remove alternator (3).

Installation:

Replace aluminum screws .

Tightening torque, see 12 31 2AZ in 12 31 ALTERNATOR WITH DRIVE AND MOUNTING PARTS .

Fig 1: Identifying Alternator Screws

Courtesy of BMW OF NORTH AMERICA, INC.