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S54 6 Cylinder Engine Alternator Replacement
 
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Pelican Technical Article:

S54 6 Cylinder Engine Alternator Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$200

Talent:

*****

Tools:

Set of sockets, 17mm open-end wrench, flathead screwdriver

Applicable Models:

BMW E46 M3 Coupe/Conv (2006)
BMW Z4 Coupe/Conv (2006-08)

Parts Required:

Alternator, drive belt, idler pulley

Hot Tip:

Work with a cool engine

Performance Gain:

Car will charge properly

Complementary Modification:

Change serpentine belt, idler pulley

A faulty or failing alternator can cause many problems, from a simple discharging of the battery to an engine drivability problem. There are a few signs and tests you can perform to determine if the alternator is the root cause of your problem. If you get lucky, your battery light (charging system indicator) will illuminate to warn you of a possible failure. When the battery light (charging system indicator) is ON, this means a voltage difference has been detected between battery positive (+) constant (terminal 30) and the ignition ON circuit (terminal 15), indicating a fault in the charging system.

It is common for an alternator to fail slowly. When this happens your symptoms will be present when the electrical system has the highest load, i.e., at night. Driving at night, you may notice the instrument panel lights dim, or the radio or headlights flicker. This is a good indication that the alternator cannot handle the excess load. Another sign of a charging system problem is that the headlights or radio dim when lowering your window. When the alternator can no longer charge the battery, you may park your vehicle and not be able to start it. Of course, this could be a faulty battery too.

Always check the voltage of your charging system under load. Voltage should be within 13.2: 14.5 volts d/c. To load, have the engine running at idle, turn on the headlights and the HVAC blower motor. Never disconnect a battery cable while the engine is running to test the alternator. You may cause damage to the alternator or other electrical components from the surge in amperage. Before performing any tests of your alternator, charge and test your battery. If the battery is faulty, your alternator tests will not be accurate.

In this article, I'll go over the steps involved with replacing the alternator on the BMW Z4 models with an S54 6-cylinder engine. Z4 models with a 6-cylinder engine may be equipped with one of several different alternators with different amperage ratings. Be sure your replacement alternator has the same rating as the faulty unit. You can usually find the amperage rating on the alternator housing.

Remember that your car may have been serviced before and had parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Be sure to work with a cool engine and disconnect the battery before beginning.

Remove the engine drive belts. See our tech article on drive belt replacing. Remove the intake air housing and ducts. See our tech article on intake air housing and ducts replacing.

The alternator on BMW Z4 models with an S54 6-cylinder engine is located on the left side of the engine (red arrow).
Figure 1

The alternator on BMW Z4 models with an S54 6-cylinder engine is located on the left side of the engine (red arrow).

Working in the trunk, disconnect the battery negative cable (red arrow) and cover the battery terminal so the cable does not accidentally come in contact with the disconnected cable.
Figure 2

Working in the trunk, disconnect the battery negative cable (red arrow) and cover the battery terminal so the cable does not accidentally come in contact with the disconnected cable. See our tech article on battery replacing for notes on disconnecting and reconnecting the battery.

Remove the idler pulley dust cap (red arrow).
Figure 3

Remove the idler pulley dust cap (red arrow). Use a small flathead screwdriver to lever it off.

Remove the 16mm idler pulley fastener (red arrow).
Figure 4

Remove the 16mm idler pulley fastener (red arrow).

Unscrew and remove the idler pulley from the engine with the long bolt (red arrow).
Figure 5

Unscrew and remove the idler pulley from the engine with the long bolt (red arrow). Install the new idler pulley. Be sure to align the tab on the pulley (green arrow) and slot on the engine (yellow arrow) and tighten the fastener.

Working at the bottom front of the alternator, locate the 16mm alternator mounting fastener (red arrow).
Figure 6

Working at the bottom front of the alternator, locate the 16mm alternator mounting fastener (red arrow).

This photo shows the bottom bolt being removed and ratchet position (red arrow).
Figure 7

This photo shows the bottom bolt being removed and ratchet position (red arrow). Working at the bottom front of the alternator, loosen the 16mm alternator mounting fastener (red arrow).

Then, wiggle the alternator as you pull the fastener out (red arrow) at an angle.
Figure 8

Then, wiggle the alternator as you pull the fastener out (red arrow) at an angle. Next remove the alternator from its mounting bracket by rocking it back and forth while pulling up and off the bracket.

Once you wiggle it out of the mounting bracket, disconnect the electrical connector.
Figure 9

Once you wiggle it out of the mounting bracket, disconnect the electrical connector. Working at the back of the alternator, disconnect the electrical connector (inset) by squeezing the release tab and pulling the connector straight off.

Then remove the alternator positive (+) cable fastener (usually a 17mm) (red arrow), and remove the cable from the alternator.
Figure 10

Then remove the alternator positive (+) cable fastener (usually a 17mm) (red arrow), and remove the cable from the alternator. Remove the alternator from the engine and replace it.

If you are reinstalling an old or used alternator, you may have to move the bushing (red arrow) flush with the mounting ear for proper fit to the alternator bracket.
Figure 11

If you are reinstalling an old or used alternator, you may have to move the bushing (red arrow) flush with the mounting ear for proper fit to the alternator bracket. The green arrow shows the bushing flush with the mounting ear. To do this, place a 22mm socket (yellow arrow) between the bushing and the ear on the back side. Install the alternator fastener through the socket. Slowly tighten the fastener to drive the bushing flush with the mounting ear. Be very careful and do not use too much force. Damage to the alternator may occur. Install a new alternator in the alternator bracket. Then install the fasteners and tighten. Attach the electrical connections to the back of the new alternator and tighten. Install the drive belt and check that the belt is properly aligned in the alternator pulley. Then reassemble the remaining items in the reverse order of the removing steps. Check the operation of the charging system and alignment of the drive belts. Install the idler pulley through the alternator and fasten it to the engine. Reassemble the air filter housing, and the intake air duct. Connect the battery negative cable.

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Comments and Suggestions:
Komenda Fan Comments: Thanks for the articles, had to replace the alternator in my Z4, this and the drive belt article helped immensely.

June 23, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 

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Page last updated: Fri 12/2/2016 02:54:13 AM