A BMW N55 starter replacement has unfortunately become a common repair in older turbocharged vehicles.
- Remove the negative terminal from the battery. Since this repair deals with the engine's electrical system, the battery must be disconnected to avoid damage to your vehicle's sensitive electronics. Not disconnecting the battery for this repair will most likely cause catastrophic damage to sensitive electronics.
- Remove the left and right plastic covers from the sides of the microfilter housing.
- Remove the four screws anchoring the upper microfilter housing to the cowl of the engine. Remove the upper microfilter housing from the vehicle.
- Disconnect the hood electrical switch from the left side of the microfilter housing.
- Remove the air sensor from the right side of the microfilter housing.
- Remove the left and right fasteners anchoring the lower microfilter housing to the body of the vehicle. Remove the lower housing from the engine compartment.
- Remove the two torx screws anchoring the intake duct to the suction hood. Unsnap the intake duct from the intake muffler and remove from the vehicle.
- Unplug the mass air flow sensor (MAF).
- It is good practice to mark connections with high visibility tape so you don’t miss any during reassembly.
- Grasp the top engine cover and pull it free from the engine.
- Loosen the hose clamp on the air duct. Unclip the lid on the intake muffler and remove it from the vehicle.
- Grasp the base of the intake muffler and pull it free from the engine. Disconnect any wiring harnesses attached to the bottom of the intake muffler and remove it from the vehicle.
- Loosen the hose clamp on the charge induction pipe. Use a pick to raise the pipe’s metal release where it connects to the throttle body. Use a torx bit to remove the charge induction pipes mounting bolt and CAREFULLY remove the pipe from the intake system.
- Turn the pipe over and remove its electrical connection by using a metal pick to raise its locking tab while pulling the plug free.
- Unplug the fuel vent valve by depressing the metal locking clip and pulling the connection free. Disconnect the plastic vacuum tube from the bottom of the valve and stow safely out of the work area.
- Disconnect the vacuum pipe from the valve cover. Sometimes it helps to use a pair of long nose pliers to release it.
- Disconnect the fuel rail sensor by depressing the locking tab and pulling the plug free.
- Use an 11mm socket wrench to remove the one mounting bolt and six mounting nuts securing the intake manifold to the cylinder head.
- Grasp the intake manifold and CAREFULLY pull it free from the cylinder head. There are a lot of wires surrounding the back of the manifold...but with patience you will be able to slowly work the manifold out without disconnecting the main wiring harness.
- Use bungee cords to secure the intake manifold out of the work area.
- Locate and identify the starter motor at the rear of the engine.
- Pull the main wiring harness free from its mounting bracket as shown below.
- Unplug the starter motor sensor by depressing its metal locking clip and pulling it free.
- Use a 12mm socket to remove the positive battery cable from the starter.
- We strongly recommend giving the starter about 20 small taps with a ball peen hammer. This will help break free the mounting bolts which are most likely seized up. We find the mounting bolts come out much easier after completing this step.
- Starting with the lower mounting bolt, use an E12 external torx socket to carefully remove it. It is important to remove the lower bolt first...this will alleviate some of the stress on the starter and make it the upper bolt easier to remove.
- We used an E12 ratcheting box end wrench to remove the upper mounting bolt. It is much easier than trying to get a socket on it.
- Using an E12 ratcheting wrench, reach behind the starter and remove the upper mounting bolt. If the bolt is stuck, give the starter a few more taps with the hammer. USE PATIENCE...the bolt is long and it takes some time to get it out.
- Grasp the starter and carefully remove it from the vehicle.
BMW N55 Starter Installation Checklist
***The following steps were performed on a 2011 335i...other models may vary.-
- Install the new starter into the engine.
- Reinstall the mounting bolts and hand tighten them.
- Torque the lower starter bolt (turbo engines only) to 38 Nm (28 ft-lb).
- As discussed earlier in this article, you will not be able to get a torque wrench on the upper mounting bolt. We use the following process to "estimate" the torque needed: apply just enough pressure to the lower mounting bolt with the ratcheting E12 wrench until it barely moves. Apply the same amount of pressure on the upper mounting bolt with the E12 wrench as used to barely move the lower bolt. This will put it close enough to the required torque value.
- Reinstall the positive battery cable on the starter and torque its mounting nut to 13 Nm (10 ft-lb).
- Plug the sensor wire back into the starter.
- Attach the wiring harness back onto its mounting bracket on the engine block.
- Carefully position the intake manifold back on its mounting studs being careful not to pinch any of the gaskets. It is strongly recommended that new gaskets are installed whenever the intake manifold is removed. Please see our parts list above for more information.
- Reinstall the intake manifold mounting nuts and bolt and torque them to 15 Nm (11 ft-lb).
- Plug the fuel rail pressure sensor back in.
- Plug the vacuum tube back into the valve cover.
- Attach the vacuum line and plug the sensor wire back into the fuel vent valve.
- Plug the sensor back into the charge induction pipe. Reinstall the charge induction pipe back into the engine.
- Reinstall the intake muffler.
- Plug the mass air flow sensor back in.
- Reinstall the engine cover.
- Reinstall the intake duct.
- Install the lower microfilter housing.
- Install the right and left electrical connections.
- Install the upper microfilter housing.
- Snap the right and left covers back on each side of the microfilter housing.
- Reconnect the battery.