This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your BMW 3 Series. The book contains 272 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any 3 Series owner's collection. The book was released in August 2006, and is available for ordering now. See The Official Book Website for more details.
There are some projects that seem like they should be relatively routine--and are very easy to perform on other cars--but are a huge pain on the BMW 3 Series cars. Replacing the starter is one of them. Most other cars I've worked on have had relatively accessible starters. If you are quick with the tools, you can have the starter replaced within 15 minutes on some engines. Not so with the 3 Series. The only way to replace the starter is to remove the intake manifold (Project 12) or remove the transmission (Project 43).
The first and most critical step in the removal process is to disconnect the battery from the car (Photo 1). This is very important, as live current is connected to the starter at all times. You can seriously injure yourself and damage your electrical system if you accidentally ground the large red wire connected to the starter.
To disconnect the battery, disconnect the negative, or ground lead from the battery. Always disconnect the negative or ground lead first--if you disconnect the positive/hot lead, there is a chance that your tool may touch the metal chassis. This could result in a short circuit, which would not bode well for you. The worst-case scenario might be if your wrench hit the chassis and was instantly welded there by the current, then the battery overheated and exploded because you couldn't break the connection. In other words, don't risk it--be sure to disconnect the ground first.
If your car has the original radio in it, be aware you will need the radio code if you disconnect the battery. The BMW dealer can look this up for you if you don't have it, but that can be a huge pain, and most dealers will charge you for the service. Disconnecting the battery may also erase fault codes stored in your DME. To be on the safe side, I recommend you read your fuel injection fault codes prior to disconnecting the battery (see Projects 28 and 29).
You'll need to remove either the manifold or transmission to access the starter. Once you have the manifold or transmission removed, the actual process of replacing the starter is not too difficult. Verify again that the battery is disconnected, and then unbolt the large, thick red wire harness that connects to the starter. Also disconnect the much smaller wire harness that plugs into the terminals on the back of the starter solenoid.
The starter is attached to the transmission case with two Torx bolts. Remove these bolts (see Project 43), and you should be able to lift the starter out of the engine compartment (if you removed the manifold first), or out the back of the engine (if the transmission was removed). Verify that your old starter looks the same as the new starter and has the same number of electrical connections on the back.
As indicated in Project 43, the nuts that hold the starter in place may be very difficult to hold when tightening up the bolts. This is definitely a job made easier with an assistant on hand. Have your assistant hold the nuts in the engine compartment while you tighten the bolts from underneath.
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The battery is located in the engine compartment on E30 cars, and in the rear trunk on E36 cars. Shown in this photo is a special BMW battery designed for the convertible (it's larger and intended to withstand increased vibration). Always disconnect the black negative, or ground, connection first (green arrow). If you are not planning to remove the battery, this connection is all you need to disconnect--there is no need to disconnect the positive/hot lead to the battery. When you disconnect the ground from the battery, make sure you place or tape the ground lead aside. You don't want it accidentally falling on the terminal of the battery while you're working and accidentally connecting up the battery again. A handy device I like to install on all my cars is a battery cutoff switch (lower inset). Installation of this switch on the battery ground allows you to remove the green knob and shut off all power to the car. An added tip: Connect a small inline fuse from one end to the other, and a small amount of current will continue to flow, keeping your radio presets from being cleared out when the battery is disconnected. The E30 battery is shown in the upper inset.
Here is the view from the top of the E36 engine compartment with the intake manifold removed. The starter is relatively easy to access at this point (the starter's solenoid shown by orange arrow); however, there are some hoses and cables that will still get in your way. The red arrow shows where the battery cable is connected to the wire harness. Danger: This wire is connected straight to the battery and is live unless the battery is disconnected. The blue arrow points to the starter control harness, and the green arrow points to one of the nuts that hold the starter to the transmission.
If you happen to have your transmission out of the car, it's really easy to replace the starter. This photo shows the underside of the engine bay when the transmission has been removed. The starter is very accessible (yellow arrow), and removing it only takes about five minutes.