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N62 8-Cylinder Alternator Replacement
 
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Pelican Technical Article:

N62 8-Cylinder Alternator Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$200

Talent:

****

Tools:

T60 Torx bit, 16mm and 10mm sockets, flathead and Phillips screwdrivers

Applicable Models:

BMW 545i Sedan (2004-05)
BMW 550i Sedan (2006-10)

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

The electrical system in your vehicle is powered by a 12-volt battery. The initial job of the battery is to power the starter motor, thus cranking the engine fast enough to start. The battery also supplies voltage to the ignition system, the fuel system, lights, HVAC system, windows, door locks and multitudes of sensors throughout the car. In order to maintain the battery in a state of charge, a belt-driven electrical generator, generally referred to as an alternator, is bolted to the engine block. The belt driving the alternator is powered by the engine pulley (vibration damper). As soon as the engine starts, electrical power is generated by the alternator and supplied to the battery to recharge it.

Generation of electricity creates a significant amount of heat in the inner windings of the alternator. This heat needs to be vented and dispersed in order to prevent damage to the alternator. Air-cooling of the alternator is used in nearly all car models and most BMW models. However, because of the high level of electrical demand and output, the alternator in BMW E60 models with 8-cylinder engines is water-cooled.

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 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 E60 8-cylinder engines. Be sure to work with a cool engine and disconnect the battery before beginning. E60 models can come with a few alternator 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. Before removing a water-cooled alternator, be sure to drain the cooling system, which is covered in a separate technical article.

Keep in mind that when your car was serviced before, parts may have been 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.

Vehicle models change and evolve as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. 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.

Working in the trunk, disconnect the battery negative cable and cover the battery terminal so the terminal 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 cooling fan. See our tech article on radiator cooling fan replacing.

The alternator is located at the left side of the engine (green arrow).
Figure 1

The alternator is located at the left side of the engine (green arrow).

Working at the intake air duct, pull the vacuum line (green arrow) off the air duct.
Figure 2

Working at the intake air duct, pull the vacuum line (green arrow) off the air duct.

Using a flathead screwdriver, loosen both of the intake air duct hose clamps (green arrows).
Figure 3

Using a flathead screwdriver, loosen both of the intake air duct hose clamps (green arrows).

Once the clamps are loose, pull the air duct off the throttle housing.
Figure 4

Once the clamps are loose, pull the air duct off the throttle housing. Then pull it off the intake air box. Place the duct aside.

Working next to the alternator, locate the drive belt tensioner (green arrow).
Figure 5

Working next to the alternator, locate the drive belt tensioner (green arrow). Using a T60 Torx bit, rotate the tensioner in a clockwise direction. Once tension is removed from the belt, pull the belt off the alternator pulley. Then remove the belt from the engine.

You now have access to the alternator (green arrow).
Figure 6

You now have access to the alternator (green arrow). Our subject vehicle has an air-cooled alternator. If you have a water-cooled model, disconnect the electrical connections at the front of the alternator now.

Next, remove the drive belt tensioner.
Figure 7

Next, remove the drive belt tensioner. This allows easier access to the alternator. Using a 16mm socket, remove the drive belt tensioner fastener (green arrow).

Remove the belt tensioner from the engine.
Figure 8

Remove the belt tensioner from the engine.

Next, remove the two 16mm alternator fasteners (green arrows).
Figure 9

Next, remove the two 16mm alternator fasteners (green arrows). Once loose, slide them out of the alternator and store them in a safe place. Note the location of the fasteners. The lower bolt is longer. Normally, you would disconnect the alternator electrical connections. However, our subject vehicle has adaptive steering and makes this quite difficult. We will disconnect the electrical connectors once the alternator is removed.

If the alternator is stuck or won't come off easily once the fasteners are removed, use a flathead screwdriver and lever between the alternator and the mounting bracket.
Figure 10

If the alternator is stuck or won't come off easily once the fasteners are removed, use a flathead screwdriver and lever between the alternator and the mounting bracket. Slide it off the bottom bracket. Then lift the alternator up just enough to remove it toward the radiator.

When removing the alternator, detach the positive battery cable (green arrow) from the bracket (yellow arrow).
Figure 11

When removing the alternator, detach the positive battery cable (green arrow) from the bracket (yellow arrow).

Place a piece of plywood (red arrow) on the radiator to protect it.
Figure 12

Place a piece of plywood (red arrow) on the radiator to protect it. With the alternator removed, tilt it so the pulley faces down. Working at the back of the alternator, disconnect the electrical connector by pressing the release tab (green arrow) and pulling it straight off. Then remove the 13mm nut (yellow arrow). Then remove the battery cable from the alternator.

Place the alternator on the workbench.
Figure 13

Place the alternator on the workbench. Lever off the idler pulley protective cap. Remove the idler pulley T45 Torx fastener (green arrow) and transfer the idler pulley to the new alternator.

If you're reinstalling an old or used alternator, you may have to move the bushing (red arrow) out of the mounting ear for proper fit to the alternator bracket.
Figure 14

If you're reinstalling an old or used alternator, you may have to move the bushing (red arrow) out of the mounting ear for proper fit to the alternator bracket. To do this, place a 23 or 24mm socket between the bushing and a vise jaw. Slowly tighten the vise 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.

Attach the electrical connections to the back of the new alternator and tighten.
Figure 15

Attach the electrical connections to the back of the new alternator and tighten. Install the new alternator in the alternator bracket. Then install the fasteners and tighten. The long fastener (green arrow) and shorter fastener (red arrow) go in the shown holes. 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. Connect the battery negative cable. Check the operation of the charging system and alignment of the drive belts.



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Comments and Suggestions:
Alex Comments: On step 14 how does that apply if I want to reuse my alternator? I just want to replace the voltage regulator since that is the only thing that is bad.
November 24, 2016
  Followup from the Pelican Staff: Follow it if reusing an old alternator to reposition the old bushing. - Nick at Pelican Parts  
Joel Comments: I have two question. 1- when removing the drive belt tension,does it have set position when installing it back? 2- do you recommend replacing the alternator bracket seal or gasket?
August 3, 2016
  Followup from the Pelican Staff: Modern BMWs have automatic tensioners, no need to set anything.

Only replace the seal if it is leaking. - Nick at Pelican Parts
 
Drogo Comments: BMW was my first car and i am verry happy for this experience. translated by https://translate.google.cz/
July 14, 2016
  Followup from the Pelican Staff: Cool. - Nick at Pelican Parts  
ATB Comments: I have 2008 E60 with N62 engine, are the bolts for the alternator reusable or are they aluminum that have to be replaced if removed? Just want to make sure I order all of the needed parts.

Thanks
June 18, 2016
  Followup from the Pelican Staff: The are steel bolts and reusable. - Nick at Pelican Parts  
Joey Comments: Thanks for the awesome write-up. Made the job so much easier. I do have a question though...I just finished installing my new/remanufactured alternator in my 2004 545i and after driving the car around the block, the car is making a whining sound below 1000 rpms. If I touch the gas and increase the rpms over 1000 it goes away. Any idea what this might be?
September 7, 2015
  Followup from the Pelican Staff: The belt may be misaligned. Is the noise coming from the belt area? - Nick at Pelican Parts  
Lemon Comments: For certified mechanic?
June 2, 2015
  Followup from the Pelican Staff: Depends on their experience. I would suggest calling a local BMW shop and asking them for an estimate. - Nick at Pelican Parts  
Lemon Comments: What is the time frame for removal and install of an alternator for 2008 bmw 550i?
May 31, 2015
  Followup from the Pelican Staff: Not sure. I would say set aside half a day. - Nick at Pelican Parts  

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Page last updated: Fri 12/2/2016 02:22:33 AM