Specifically, on the E39 2.8L M52, but there are a lot of similarities for other engines. This repair is notoriously frustrating, with limited room to work underneath the intake and up against the firewall.
There are a lot of step by step threads and articles on the net which I will link at the bottom for more reading.
- (obviously) Engine not starting. Can be intermittent.
- A whirring/whizzing sound as the starter spins but is not engaged
- A grinding while cranking can be a warning sign. You may think the flywheel is missing teeth, but the starter cog is designed with a softer material to fail first and, most likely, your flywheel is fine.
- The new starter. Duh, right? But actually, this needs to be mentioned. These are available with either threaded or thru holes. The 2 mounting bolts run through the transmission bell housing and to the starter, where they either thread directly in or will need a nut on the backside. The threaded is recommended to save headaches, but check what is on your car. You may need different bolts. Speaking of which...
- Getting new bolts isn’t necessary, but it also isn’t a bad idea. Some sources say they are one-use-only. Technically, all bolts are one-use-only in critical areas in order to get accurate clamping forces. But these bad boys are M12 x 1.50 x 70mm, which isn’t a common thread size that you can find at a hardware store, so you may need to order them ahead of time. Also...
- The bolts have an E14 external Torx head, which I didn’t even know existed before doing this. I actually had a hard time finding a set of these sockets at local stores. DO NOT USE A 12 POINT SOCKET. It will strip. (EDIT: The 3 series typically uses a size E12, M10 x 1.25 x 65)
- Penetrating oil
- Metric wrenches and sockets (8mm, 10mm, 13mm)
- Very long (3') socket extension or a u-joint socket, depending on your method
- I used a swivel headed socket handle (a ratchet that doesn’t ratchet) like this one.
- Zip ties to hold hoses and wires out of your way
This method will greatly improve your access to the starter, and will be the easiest to remove the failed part. I chose this method on my E12 because the intake was already removed when I bought the car. I still had to wrestle with wrench access for the mounting bolts and wire connections, and it was difficult to maneuver the part in and out of place.
The problem with this method is the added time and risk involved in further disassembly. If you aren’t careful, more parts could be damaged and end up costing you.
Sort of. From the bottom, you cannot see the top mounting bolt or the top wire connection. I ended up removing the air cleaner box, MAF, and intake boot up to the throttle body, because I had to replace a couple hoses for the idle control valve anyway. It was also a huge help to remove the duct that runs from the driver-side cabin air filter to the firewall. That gave me access to the bolt from the top.
While under the car, you will still be battling the subframe, suspension components, and the steering column. Falling wrenches hurt.
It goes without saying that you will need a jack and jackstands for this method. I had to build some MCM style ramps to get my jack under the car, because my jack is not low profile. You may also need those really long extensions, but more on that later.
Go to a trusted mechanic or dealership. This repair is a giant pain in the ass as a DIY. The downsides here are that it will cost you with part mark-ups, around 3 hours of labor, and possibly a tow to the shop. You might be able to avoid the tow truck with a bump start (if you have drive stick) or by hitting the solenoid with a hammer to try and get it to engage.
First, disconnect the battery. Then remove anything that will help you get better access. Then, have any of your stress-relieving methods at hand, whether they be mental, physical or liquid.
There are 4 wires that connect to 3 posts on the starter. Each is a different size, which helps when you go to put the new one on. On the new part that I had, which came with the car, the smallest stud (for the solenoid ground, on the top of the solenoid) was a bit too long. It made it very difficult to get the little 8mm nut on while peering through the intake to see it. A magnet helped, but I still dropped it a dozen times. The rest were pretty straight-forward.
Now, let me talk about those external torx head mounting bolts. Here are the difficulties that you face:
- Cramped space, limited visibility
- Surrounding components that inhibit wrench alignment and motion
- The bell housing will not allow an average socket wrench to fit over the head straight, so you need an extension, but...
- You are too close to the firewall to use even a 3" extension
So, most write-ups call for 3 feet(!) of socket extensions. The extensions can travel down the tunnel along the side of the transmission until you have enough space to turn the wrench somewhere around the driveshaft.
I did not have 3' of extensions. My method used a universal joint socket. Even with that, my socket wrench could not fit because of the aforementioned bell housing, so I used a swivel headed socket handle (side note: I did try using this socket handle directly onto the bolt without the universal joint but it was still too large and hit the bell housing).
This combo can be frustrating to get it lined up and allow the transfer of torque, but it can be done. A piece of pipe is necessary for leverage. I used the handle for my jack. All the while, you are up to your shoulders in the engine bay and trying push hoses out of the way so you can turn the wrench.
Possibly, a set of deep-well external torx sockets would be able to get in there. Or a set of torx wrenches. Maybe. I cannot confirm that, nor could I find those anywhere locally.
You drop the old part through the bottom, and that’s it. Just 2 bolts and 3 wire studs. Sounds easy, right?
This was one of those times where the frustration to satisfaction ratio was very bad. Then I remembered how much money I’d saved over bringing it in, and I felt a little better. Of course, then I drive it and I forget why I was mad in the first place.