N52 Starter Motor Replacement

lucasxdiniz

Active member
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.

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

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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.

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

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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.

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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.
 
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!
 
kab said:
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
 
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:
 
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?
 
ted928 said:
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.
 
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
 
I’m just about to start doing this on my silver top N52.
I can barely see the starter motor and after reading the above can’t see how you would (a) be able to even reach into to get to it and (b) unattach everything and take it out.
I plan on removing the manifold as I hope it will give a bit more visibility.
Fair play to those who have done it like above.
 
chanlon1 said:
I plan on removing the manifold as I hope it will give a bit more visibility.

I did the same on my silver top. Remove manifold, don’t break the PCV lines and cables, replaced the starter (also replace the bolts, single use!), revised the alternator, replaced intake gaskets, replaced both DISA’s and the PCV system. Get it all out once and you’re good to go for many years to come on that end :thumbsup:
 
Waiting on fresh bolts currently so I just wanted to hop on here and provide some additional comments about my personal experience with this job that may be helpful to others.

First of all, this is a great guide. I followed along with this and watched a couple of youtube videos to swap my starter out and they were very useful resources. I think access to the *proper* tools is huge for this job because of the limited space but I was also able to kind of Frankenstein things together to make what I have work. I've outlined specific things I experienced during each step in the process in hopes others can eliminate some of the guesswork.

Starter Bolts
My bolts were very tight. I used PB Blaster and let them soak but still needed to use a breaker bar (top half of my floor jack lever) to get them loose and then unscrew by hand from there. Honestly plenty of room to work here.

Positive Wire Nut
The nut holding my positive wires on was harder to remove than the starter bolts. This was due to a much more cramped area to work in beneath the manifold as well as the angle of approach required. After a few failures to get enough leverage and bite on the nut, I found a solution that worked for me. I used a deep well socket (as suggested) attached to a swivel adapter which was attached to 2 long extensions and then ultimately the ratchet. I then fed this "apparatus" through the 3rd space between the manifold pipes and secured a solid grip on the nut while propping the front of the starter upward with my right hand. I started with the 2nd space in the manifold, more directly over the starter but found that the swivel mount being at such an aggressive angle (almost 90 degrees) was too harsh for it to spin smoothly which is key. It was a very "clunky" turn at the end of the contraption I had made. Going in from the 3rd space created closer to a 45 degree angle or less and a smoother rotation when coupled with angling the starter upward as well. This finally broke the nut free and I spun it off and unhooked the wires easily from there.

Negative Wire connector + spring clip
Removing the spring clip with a flat head was simple. Caught it with one of those magnetic telescoping tools- a CRUCIAL item to own. Unhooked the connector by pushing it off with my thumb. So the removal process for this piece was maybe the easiest of the entire job.

Putting it back onto the new starter however, felt like a scene from Mission Impossible lol I used a long screwdriver to fish the connector that had been tucked off to the side back near to where it needed to be and just barely fingertip-attached it in place. For the spring clip, I again used the magnetic tool to carefully maneuver the clip to be above the starter motor through the space in the manifold. It felt like I was playing one of those claw games in an arcade. Hunched over and peering through another space in the manifold to get a proper line of sight, I lined it up to hover over its final position. From here it took a ton of patience and many tries before I successfully pressed it into the slot it belongs in to secure the connector. For me, it took every bit of stretch in my right arm to reach far enough to make this happen.

As I said, I write this hoping anyone considering tackling this job on their own can take notes from my struggle with it and have an easier time. It's really not a bad job as others have said. You just need patience and proper tools or you may have a longer road ahead of you.
 
Photos to help illustrate some of this -
 

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Barty said:
I did the same on my silver top. Remove manifold, don’t break the PCV lines and cables,

When I changed my starter, I couldn’t remove the manifold completely. There was still one of the PCV pipes that attaches to it and attaches to something below that I just couldn’t remove. Fortunately I was able to move the manifold a few inches to the side to allow access.
 
A quick addendum to this useful thread and note I am making some assumptions here so if I’m wrong- I apologise

I went to do this on my coupe a few weekends ago- try as I might once if undone everything I could not manoeuvre the starter motor out of its hole under the intake manifold. Preventing movement was a sensor wire and several parts of the ccv system

I revisited this weekend and popped the intake manifold off (a much simpler task that I envisaged) and the subsequent removal was very easy

I also took the opportunity to change the intake manifold gaskets and the intake body gasket

Mine is a silver top- I think the OP had a black top n52
 
Thanks for the write up lucasxdiniz!

I have a 2004 3.0i - E85 w/ M54B30 engine which isn't quit the same as your N52 and vehicle. It got me close enough. After every small accomplishment I took a break which I needed and did more searching and reading on the internet.
 
bigwinn said:
Mine is a silver top- I think the OP had a black top n52

Mine's a silver top also, but there was a CCV pipe attached to the underneath of the manifold that I couldn't release, but was able to to move the manifold out of the way enough to access the starter motor.
For the life of me I just couldn't fathom how to release said pipe and the fact I was doing it blind as I couldn't see it, didnt help.
 
Thanks to the recent posters for bringing this back to the main page....my starter motor has stuck a couple of times in the last couple of weeks so I might have to take this replacement on. The guide looks great to kudos to the author...very helpful
 
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