Replacing the alternator on BMW Z4 E89

I was enjoying a drive near Esk when I had this warning pop up:

Charging fault: Battery no longer being charged. Switch off electrical devices that are not required!

along with this one:

Transmission position P possibly not available. Operate parking brake when car stationary.

I’d recently connected a CTEK bluetooth battery monitor, so I checked the app and it showed 12.2volts, which is nearly flat for a 12v battery.

At first I wasn’t too worried because I figured the battery itself was the problem. It was in the car when I bought it and who knows how long it sat idle at the dealer.

I started making my way home and realised the car wouldn’t let me turn on the aircon. Then I checked the voltage again and it was at 12volts.

Seems the alternator was the issue, which meant I only had the charge left in the battery to get me home. It was about a hour and a half drive.

I decided to try to make it. I figured if I damaged the battery it would be cheaper to replace it than get a tow truck.

It was a stressful drive. I would stop and check the voltage from time to time and it was constantly dropping.

It reached 11v when I was about 15 minutes from home. I thought the engine would surely stall if it dropped lower, but soon after I was pulling into my garage with 10.6v showing on the battery. Amazing!

I immediately put the battery on charge but it was no use - it was damaged and wouldn’t hold a charge anymore. At least it got me home.

I wanted to completely rule out the battery as the problem so I bought a replacement Century 70Ah AGM (DIN65LH).

I had a Century 270Ah deep cycle in my campervan and it was very reliable, so I was happy with the brand, and it was on a good discount at the time too.

Installation is really easy - access is in the boot. I coded the battery change using bimmerlink and went for a rainy drive to see if the error went away, but sadly it did not.

The Z4 looks special to me in the rain. For many years my desktop wallpaper was this promotional picture:

One day I’d like to recreate this picture!

Replacing the alternator on a BMW Z4 E89 N54 2009

Anyway, back home and onto the internet to find a new alternator. I find with the Z4 that most parts sites don’t list many items for it. Instead I search under BMW 335i since it has the same engine.

I thought that a Jaylec 65-1778 would fit, and called AutoCave who very helpfully confirmed the fitment and arranged so I could collect it from the warehouse at Caboolture.

Mr P Inspecting the goods

The reason I decided to take on this job myself is this YouTube video, which shows how you can replace the alternator easily by just cutting a small piece of plastic. I suggest you watch this video.

On the Z4 it’s actually even easier as the charge pipe is routed differently, and there’s more access to the engine thanks to the giant front end.

I’m an amateur at this - the most I’ve done until this point is replace a VANOS solenoid. I was keen to learn more but as you’ll soon see it went a bit wrong.

Getting the old alternator out

If your car is automatic or DCT, put the front up on ramps or jacks, as you’ll need to get underneath to loosen the AT cooler from the fan.

Disconnect your battery before proceeding any further!

Start by removing the plastic air piping and airbox. There’s some screws, some piping with clips, and some screw clamps. You don’t have to dismantle the airbox/filter but I did because I have no idea what I’m doing.

Once the airbox is out, you can see the alternator better. Next you’ll need to get access to the front of the engine by removing the cooling fan and loosening some piping.

Remove the bracing above the radiator. There’s three screws on either side.

Remove three screws from each side

Remove the screws securing the insulation under the front of the car, and remove the screw attaching the AT cooler to the fan.

At the top of the fan, there’s another screw to remove on the top left. Lastly disconnect the power cable. Then you can slide the fan up and out. There’s two plastic clips that hold it in place on either side.

Next you’ll need to loosen the piping that crosses in front of the engine. There’s two bolts with grommets for insulation.

Now you can move the serpentine belt tensioner to loosen the belt off the alternator.

Make a drawing of how the belt is routed so you can refer to it if it slips off.

Turn the tensioner clockwise. It will flex and you can slip the belt off.

Disconnect this pipe with the twist lock fitting.

Now you have access to remove the four bolts that secure the alternator.

This is where things went a bit wrong for me. My lower right hand side bolt sheared at the threads, leaving the hole partially filled. I’ll talk more about what I did to fix that later on, but for now will carry on with the instructions.

With the alternator loose, you’ll find you can’t remove it due to the plastic airbox mount.

The answer is to use a Dremel to cut away a small wedge to make space. Put a rag underneath to catch the plastic shavings.

This is a very zoomed-in picture. Its quite a small cut.

Once done you can disconnect the two alternator cables, and remove it!

Here’s a short video that shows the maneuver: https://youtube.com/shorts/2Xd0vpKWfgA?feature=share

Now reverse the process to reinstall.

This job took me about four hours and I was figuring stuff out as I went along, excluding the time spent fixing the broken bolt …

The bastard bolt

How to remove a sheared bolt?

Well I tried about everything.

The challenge was the very tight space. Most tools were either too short, or too long, such that the guide hole for the bolt got in the way.

Easy-outs wouldn’t reach, so I tried using a right angle adapter, but it would just slip.

I tried drilling a hole and hammering in a torx bit, however it didn’t grip either.

I tried welding on a nut, but each time it would just shear off. After five attempts I gave up.

I could drill the bolt out, but had no way to re thread it. The tapping tools wouldn’t reach.

I kept googling and learned about tap-serts which are a self tapping insert. You drive them in with a bolt. Problem is they require a much larger hole. The M8 bolt hole would have to be drilled out to 11.5mm, which is a lot of material to lose.

I found an alternative called Seal-Lock which is much thinner - only 9.5mm.

I drilled out the hole after watching this great video on drilling metal.