Terrible startup noise

[williamsboi]

Engine was making a faint whine/moan sound, so I turned the car off and tried to restart. Got this terrible noise when I tried to restart: https://youtu.be/XzWABYITrqQ

Any idea what it is?

[osc911]

You sure it's not the passenger!!! Sorry I had to.

Did it stop after a second by itself? It could be a relay bouncing? Or the fuel pump. Can you locate the rough area the noise is coming from?

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[williamsboi]

After noticing a similar noise in another video at https://www.bimmerfest.com/forums/sh...d.php?t=261604, I tried the method suggested in that thread (priming the fuel pump), and my car started right up. However, it kept making an awful sound in the engine compartment. The sound is coming from the area in the video at https://youtu.be/PBi2aeNsnZk

As you can see, it sounds roughly like a lawn mower. After making that video, I shut the car down and attempted to restart it. It made the same noise as in this video, except slightly worse, and stalled out.

- - - Updated - - -

After noticing a similar noise in another video at https://www.bimmerfest.com/forums/sh...d.php?t=261604, I tried the method suggested in that thread (priming the fuel pump), and my car started right up. However, it kept making an awful sound in the engine compartment. The sound is coming from the area in the video at https://youtu.be/PBi2aeNsnZk

As you can see, it sounds roughly like a lawn mower. After making that video, I shut the car down and attempted to restart it. It made the same noise as in this video, except slightly worse, and stalled out.

[williamsboi]

This is the area the noise is coming from:

1024px-BMW_M62B44.jpg

[geargrinder]

yo bo-eeeeeei.

What year/model car are you talking about here. According to your profile you have "none" cars so this must be an imaginary E39.

[williamsboi]

It’s a 2003 540i-6 with 75,000 miles

[geargrinder]

OK - so TU then. (might want to put that in your profile instead of "none").

Oh wait - I just saw your 2nd video (I thought that was a link to another '3rd party'). Sounds to me like your SAI valve maybe is stuck open and barking exhaust leak down the SAI tubes (or one of the tubes is broken...)

Is it different on stone cold starts (when the SAI system runs) vs warm starts (when it wont?)

[williamsboi]

Ok, I let the car sit for a day and did a stone-cold start. The results are at https://youtu.be/X2BhL_enOi4. Note that in that video the engine starts and runs (I’m not holding the key in the start position). This time there was some smoke coming from the engine. In the name of science I gingerly fished around under the hood with my bare hand to feel for the source of the heat, and it was what I think is the alternator pulley. It (the part I’m pointing to in the attached photo) was scalding hot after the engine ran for just the few seconds shown in the video, whereas all the other pulleys and metal surfaces around it were still cold. What does that mean?

C2968D0C-700A-42AC-A945-9B17941178B4.jpg

[geargrinder]

Great work brother. If the alternator bearings crap out it can seize the alternator and yeah make a terrible noise and burnt rubber smells.

[williamsboi]

Thanks a lot. In that case, is the fix to replace the pulley or the whole alternator?

[geargrinder]

You can do either. Its not the pulley per se, its the bearings inside the alt. You pull the alternator and try to rebuild it. Its not a 'factory approved' process but it can be done.

https://www.bimmerforums.com/forum/s...led-alternator

The standard route is to get a Bosch rebuilt warrantied alt and just whack it in there... then you know you have a new voltage reg and everything... That's honestly the way I'd go... then if I didn't need to return the core (you usually do... or it costs you) I'd maybe rebuild the old one in my spare time....

Amusingly enough this is how my alternator died - horrible sound at startup in a parking lot one day - but I always forget that as an option for "sudden horrible startup noise"...

[williamsboi]

I think I'll go ahead and replace the who alternator as you suggest. Is it an easy DIY, or does it reply a lot of mechanical skill/experience? Are there any special tools required, like this one:

https://www.bimmerworld.com/Tool-Kit-4000338100.html

Also, do I need a liquid-cooled alternator?

[geargrinder]

It's not super hard but neither a super easy novice job.

Bit of stuff has to come off to get to it. None of it super hard either but again not the easiest alt as things go.

Yes you have a water cooled alt. That’s all that will fit your car. But that’s not as complicated as it sounds. Just means you have to drain coolant first, and it has a boatload of small bolts around it instead of like 3 big ones that an air cooled would.

You dont need the alt pulley tools, the new one should come w the pulley on it and ready to go.