I didn't have a camera today so this won't really be a DIY, just what I learned doing this that would've helped me out had I known. I found lots of info about the starter on an e46 m3, but there wasn't much on the z4m.
The nice long hood on the Z makes doing this repair very easy. You can remove the starter from the top of the car, and you don't need to remove anything else to get it out. I have small hands and was able to do this with a little frustration, if you're having a hard time you can take the intake manifold off.. yeah me neither.
Tools you'll need:
- a small 1/4" drive flex head ratchet. You'll need the flex head.
- an E12 socket (1/4" if you can find it, I used a 3/8"+adapter)
- 8mm and 10mm short sockets
- 10mm and 13mm deep sockets
- something to pry with, the thinner the better
Disconnect the battery in the trunk. You need to remove the panel covering it to access the neg terminal. There are black plastic screws on the panel, 8mm, securing a round clip. Loosen the screws and pry out the round clips. There are 3 nuts on the top plastic piece as well, 10mm. Remove them and pull the panels off of the battery. Disconnect the negative terminal, 10mm. Stick the neg cable somewhere stable, where it won't wander back to the terminal on it's own while you're working.
The starter motor is located on the back of engine, on the drivers side. I'm sorry I don't have a picture, but it's mounted on the same flange as the transmission, sort of under the intake manifold. You can follow the power cable going to it, it has a black plastic tube around it. It's a little awkward, but you can definitely reach it well enough to do the job.
The starter housing is held in with 2 bolts, E12. Use the flex head ratchet and you can immediately get to both of them. Remove the bolts, and note that there is a metal bracket that is being secured by both bolts as well. The bracket is also attached to the starter power cable.
I was able to move the starter at this point to get a better angle on the nuts securing the cables to the solenoid. There are 2 nuts you need to remove, a 10mm and a 13mm, use the deep sockets. Take note of how these cables fit together before disconnecting them. The 10mm secures 1 cable (ground), the 13mm secures 2 cables (power).
With everything disconnected, my starter came out easily. If yours is stuck, you might need to pry a little by the dowel pin to break it loose. Pull that sucker out.
Installation is the reverse. Make sure to move all of the cabling out of the way of the starter when you put it in. The small cable can get stuck on the wrong side of the solenoid if you aren't careful.
When you're done, start her up, hear her
purrr, and feel good
FWIW, Autozone has a replacement starter for $150 with a lifetime warranty. Certainly works for me.