Lotus99

I don't even know what the part is / does... Which would be my first question.

I've noticed these white deposits on it, and I wiped them off once, and they came back a week later. They're like the deposits you see on AA batteries that have leaked...

The car doesn't get driven every day (every few days probably), and we live in the Pacific Northwest, so it's quite wet and rainy these days (car's parked outside all the time).

My other car, which is a 335, has the exact same engine, and is parked in the garage overnights but outside during the day at work, and doesn't have the same deposits. So I'm a bit puzzled what they are / is going on...
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pcy

Oxidation.
Chemicals+salt added to melt snow/ice contribute/promote that oxidation.

Lotus99

Good point... Forgot to mention this car gets driven mainly on weekends when we go up to the local mountains, and they salt the highway. Whereas my 3 series only sees city driving, and we get almost no snow here, so they rarely salt the streets.

So it sounds like that's it, and nothing to worry about?

PS What is that part? And there's another one below it, somewhat visible. Is it the starter?

pcy

That looks like oil cooler.
Starter is not on the front of the engine.

Lotus99

Hmmm... The part on the right side, seems to have wound coils in it, that's why i figured it was some sort of motor.

pcy

The part with copper windings inside is Alternator.

Lotus99

KyleB

correct.

tonyb635

I would say more like something to be concerned about. It's corrosion and any kind of corrosion is not a good thing. You could possibly have problems with things like wire connections and connectors if left unattended. My son is in Cleveland, OH finishing up med school and his wife had a honda accord that had the same condition but much worse because it was just left that way. They were constantly having issues with connectors etc. of course there car was much older but that's my point. You can google and there is a spray on cleaner that will help keep the corrosion down. Search for aluminum corrosion cleaner etc and you should find plenty of choices. I personally don't see anything wrong with it at the moment but maybe a few years down the road....?

Lotus99

Tony, thanks for the perspective. I hadn't thought of that issue... Luckily, we only have the salt maybe 4 months of the year here, as opposed to back east, where it's more like 6 to 7, but still.

An alum specific spray is a good idea, rather than plain WD40? WD40 in theory should be ok:

What surfaces or materials are OK to use WD-40 Multi-Use Product on?

WD-40 Multi-Use Product can be used on just about everything. It is safe to use on metal, rubber, wood and plastic. It can also be applied to painted metal surfaces without harming the paint. Polycarbonate and clear polystyrene plastic are among the few surfaces on which to avoid using a petroleum-based product like WD-40 Multi-Use Product.