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N52 Starter Motor Replacement

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lucasxdiniz
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N52 Starter Motor Replacement

Post by lucasxdiniz » Mon Jul 29, 2019 12:12 am

Removal: 20-60min
Installation: 15-30min

Tools you will need:
  • 1/4" Ratchet + Extensions
  • 3/8" Ratchet
  • E14 Socket
  • 13mm Socket
  • 6mm Socket
  • Flathead Screwdriver
Tools you might need:
  • T15 torx if you have a sound generator installed
  • Snips of some sort to strip the negative wire*
  • Crimping tool recommended, pliers would work too*
  • Insulation tape*
Where to buy your starter motor:
  • BMW ~£350
  • ECP £80-£158 (Might vary wildly with different promo codes and some brands have a refundable surcharge)
  • Autodoc.co.uk £60-100 (German company)
  • West Lancs Auto Electics £96

HOW TO:

A great deal of this DIY is knowing what you're trying to remove, and how to access it. So the next few images will hopefully make this clear as not many have seen a starter before.

Note that the images make reference to front, rear, and side views; these correspond to the front, rear, and side of the car respectively.

Figure 1 shows the two areas of the engine bay to which you will need partial access. Area A is where 99% of what you'll be working on is, and area B is just used to help slacken some cables, or pull the negative connector out* of Area A. Within Area A you will locate the starter motor, please see figure 2.

Image
FIGURE 1: View from where the person working on the car would stand throughout this DIY

Image
FIGURE 2: Starter motor location.

Now that you know where to find the starter motor, here's what it looks like and all the bolts and connectors you must undo.

Figure 3 shows the two bolts that attach the starter to the bell housing. Bolt 1, highlighted red, is a very long bolt in a relatively tight space, and it can be hard to locate as there are similar bolts all around the bell housing, so to make this 'how to' idiot proof, figure 4 should highlight its location. Bolt 2, highlighted green, is a much smaller than bolt 1, and it is easily located and easy to remove.

Image
FIGURE 3: Starter motor rear view showing flange that's used to attach it to the bellhousing. Red = Bolt 1, Green = Bolt 2.

Image
FIGURE 4: Bolt 1 location

There are three wires attached to the front of the starter motor, two thick red wires are bolted onto the positive terminal of the starter (see figure 5), and one thin black wire is connected to the negative terminal (see figure 5) with a plastic connector.

Image
FIGURE 5: Start motor front view showing the electrical connectors. Blue = Pos Terminal, Yellow = Neg Terminal.

Now you should know what you're tackling, so here's a step by step that worked for me.

Step 1: Disconnect the positive terminal of your battery

Step 2: Use a flat screwdriver to remove the top cover of the air box, it's very self-explanatory. Disconnect the MAF connector. Use a 6mm socket or a small flat screwdriver to loosen the jubilee clips to remove the rest of the intake pipes/sound generator.

Step 3: Place an E14 socket onto bolt 1, then attach your (3/8") ratchet to the socket and loosen the bolt. There's not enough space to place the socket onto the bolt whilst it's attached to the ratchet. Once the bolt is loose, undo the rest by hand. It's quicker, and you don't have enough space to finish undoing it with a ratchet.

Step 4: Undo bolt 2 with an E14 socket.

Note that bolt 1 should be undone before bolt 2 so there's less load on bolt 1 and it can be undone by hand once loose.

Step 5: Pull the starter motor frontwards out of the bellhousing.

Step 6: Once it's out, manoeuvre the starter motor rearwards to create more room for your hands to reach the electrical connectors. You may need to use Area B to slacken the cables of the starter motor so you can move it more freely.

Visibility is poor for the next few steps, so use a torch and the space inbetween the plenums of the intake manifold to see what you're doing.

Step 7: The negative connector has a spring lock, use a flat screwdriver to lift it out of the connector. Remove it completely (it's fine if it falls, you will be able to retrieve it once the starter is out), then it can be pulled out from the starter motor with only one hand.

Step 8: Once that annoying connector is off, it may take you a while to do it with one hand, you will be able to put a 13mm socket in a 1/4" ratchet on the positive terminal. The end of the ratchet will need to poke out of one of the spaces inbetween the intake manifold plenums. Very little room to move the tool so undoing the nut might take a while. A 13mm ratchet spanner will not fit the nut.

Step 9: Slide the alternator/battery cable out of the bolt in the alternator. Now you should be able to remove the starter motor out of the engine bay. First bring it towards you at the same level it is placed, once you clear the engine, you should be able to bring it up.

Step 10: If your starter replacement is an identical part to the OE part, then installation is exactly the reverse of removal. If your replacement has a different negative terminal connector, then read on.

Step 11: Pull the negative/ignition cable out of the engine bay through Area B. Once you can easily work on this cable, cut the stock connector without wasting any wire length. Strip approximately 10mm of cable and place it inside the female crimp connector, use a crimping tool to crimp the connector to the wire. Wrap insulation tape around it, just leaving the very end of the connector exposed. Guide the cable back to where it should be - think you're trying to hug the intake manifold and you'll manage.

Step 12: Installation should be the opposite of removal, however, you might find it easier to install the positive wires first, being careful on how they are positioned so then the negative terminal can be connected to the male connector in the starter motor.


*Only required if the replacement starter motor has a different connector for the ignition wire.
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ph001
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N52 Starter Motor Replacement

Post by ph001 » Mon Jul 29, 2019 9:56 am

Amazing guide!!!! Big kudos to you for putting together and sharing :thumbsup:
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N52 Starter Motor Replacement

Post by kab » Fri Nov 08, 2019 4:38 pm

Thank you! I’ve just replaced mine by following your instructions. A daunting task made much easier, especially as most YouTube videos on it involved taking half the engine apart!
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N52 Starter Motor Replacement

Post by maxman » Fri Nov 08, 2019 6:51 pm

I have just seen this,very comprehensive guide :thumbsup:

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lucasxdiniz
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N52 Starter Motor Replacement

Post by lucasxdiniz » Fri Nov 08, 2019 9:33 pm

kab wrote: Fri Nov 08, 2019 4:38 pm Thank you! I’ve just replaced mine by following your instructions. A daunting task made much easier, especially as most YouTube videos on it involved taking half the engine apart!
Basic maintenance on 3-series BMWs is a nightmare in comparison to the Z-series. Glad this helped someone. :D
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N52 Starter Motor Replacement

Post by MakesMeSmile » Sun Nov 10, 2019 8:46 pm

My son is replacing mine next weekend and he suggested I look on here first to see if there is a way of removing it without taking off the manifold. This guide is great, thank you so much. Should make his life a lot easier. :thumbsup:

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N52 Starter Motor Replacement

Post by ted928 » Tue Jun 28, 2022 1:45 am

What are the bolt torque specs?
I downloaded 'BMW Z4 2.8i3.0i3.5i3.5is 2009-2016 Workshop Repair & Service Manual.pdf' and it says to replace aluminum bolts and table 12 41 states a torque of 38 Nm. When I tried to install new aluminum bolts, the bolt snapped before I reached the target torque. I checked the calibration of my torque wrench and it is accurate. Is 38 Nm for steel bolts and there is a different spec for the aluminum bolts?
2009 Z4 S-drive 30i E89 N52

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lucasxdiniz
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N52 Starter Motor Replacement

Post by lucasxdiniz » Tue Jun 28, 2022 11:38 pm

ted928 wrote: Tue Jun 28, 2022 1:45 am torque of 38 Nm
I don't know what the torque spec is for those bolts - I tightened them by feel.

There aren't any ally bolt maximum torque charts as far as my 2min Google could find, but for the sake of quick comparison a 4.6 grade bolt has a yield strength of 240MPa which is close to the average yield strength of Al alloys (170-500MPa). The maximum suggested load for a 4.6 M12 is 38Nm... but a lot plays in bolted joint calcs. Al is less stiff than steel and I am sure that would give more bolt stretch for the same applied torque, thus higher stress on the shank so I'd assume the maximum torque to yield an ally M12 should definitely be less than 38Nm.

Googling "N52 started motor bolt torque" gives 20Nm + 90 deg. I haven't checked this against anything.
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N52 Starter Motor Replacement

Post by Zedebee » Wed Jun 29, 2022 8:24 am

Great write up lucas

Torque specs from NewTIS:
“Bolt 1” M10x85 20Nm + 180deg
“Bolt 2” M10x30 20Nm + 90deg
Battery positive lead to starter M8 13Nm
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N52 Starter Motor Replacement

Post by ted928 » Wed Jun 29, 2022 10:42 pm

Thank you both very much.
2009 Z4 S-drive 30i E89 N52

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N52 Starter Motor Replacement

Post by JamesClements » Tue Sep 27, 2022 12:36 pm

Comprehensive write up will be giving this a go soon :thumbsup:
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