12 31 020 Removing and installing or replacing alternator (M52, M52TU, S50US, S52, M54, M56)

WARNING: This page is about a different car, the 2002 BMW Z3 and 2001 BMW Z3. However, it is still accessible from the selected car via links, so may be relevant.

Necessary Preliminary Tasks:

Read out stored fault messages.
Switch off ignition.
Follow instructions for disconnecting and connecting battery. Refer to 12 00 ... INSTRUCTIONS FOR DISCONNECTING AND CONNECTING BATTERY .
Disconnect and cover battery negative terminal.
Remove suction filter housing. Refer to 13 71 000 REMOVING AND INSTALLING INTAKE FILTER HOUSING (M54) .
Remove fan clutch. Refer to 11 52 020 REMOVING AND INSTALLING/REPLACING FAN CLUTCH (S52 / S54 / M52 / M52TU / M54 / M56) .
Remove alternator drive belt. Refer to 11 28 010 REPLACING ALTERNATOR DRIVE BELT (M52 / S52 / M52TU / M54 / M56) .

If necessary, drain supply tank for power steering pump, remove with holder and place to one side.

NOTE: Lines on supply tank for power steering pump remain connected.

If fitted:

Remove air hose.

Fig 1: Removing Air Hose

Courtesy of BMW OF NORTH AMERICA, INC.

Version 1

Take off cap on connections.

Disconnect plug connection (1).

Fig 2: Identifying Plug Connection

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Release nut (2) and disconnect battery positive lead.

Tightening torque, 12 31 1AZ. Refer to 12 31 ALTERNATOR WITH DRIVE AND MOUNTING PART .

Version 2

Unlock and detach plug connection (1).

Fig 3: Disconnecting Plug Connection

Courtesy of BMW OF NORTH AMERICA, INC.

Release nut (2) and disconnect battery positive lead.

Tightening torque, 12 31 1AZ. Refer to 12 31 ALTERNATOR WITH DRIVE AND MOUNTING PART .

Fig 4: Disconnecting Battery Positive Lead

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Version Without Idler Pulley:

Release alternator screws in succession while simultaneously gripping alternator firmly.

Fig 5: Removing Alternator Screws

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Remove alternator.

Version with idler pulley:

Remove cover from idler pulley (1).

Fig 6: Removing Idler Pulley Cover

Courtesy of BMW OF NORTH AMERICA, INC.

Release screw and remove idler pulley (1).

Release screw and remove alternator (2).

Version with idler pulley:

Installation:

Turning lock of tensioning roller must engage in alternator groove.

Interrogate fault memory of DME control unit.

Now clear the fault memory.