02Pilot
SuperDork
12/26/19 4:27 p.m.
Giving my 128i a quick once-over in anticipation of leaving for a trip up to Maine tomorrow morning. With the hood open, there's a slight but noticeable whine from the alternator. It's not loud enough to hear in the cabin; frankly, is it loud enough that anyone not attuned to listening for untoward engine noises would likely notice it. But it's there (confirmed source with improvised engine stethoscope). I can't recall ever hearing before, but I don't spend a lot of time standing over the engine while it's running either. Voltage output is fine at ~14.8v. As far as I know, the alternator is original (the belt and pulleys are recent).
Drive it (~300 miles each way) or take my GF's Mazda 3?
Are you a gambling man?
Just to see, check if there is a difference with the system loaded and unloaded (blower and high beams).
If you're going to be worried about it the whole time I would leave it. Car anxiety is no fun.
02Pilot
SuperDork
12/26/19 8:34 p.m.
No difference loaded and unloaded.
We're going to take her car. It would probably have been fine, but after having a car fail spectacularly 800 miles from home on a road trip a bunch of years ago, I'm always hypersensitive to odd noises and imagining the worst is just a mile down the road.
I'll keep an eye on it once we get back - with any luck it will wait until it's a little warmer to fail.
In reply to 02Pilot :
An additional test you can do is to remove the belt and slowly turn the alternator pulley by hand, feeling for any rough spots on the bearings. You can also check for any excessive side-to-side play on the shaft as well. Look at the pulley- is it wearing abnormally? A slight misalignment can cause strange noises galore...
02Pilot
SuperDork
12/27/19 6:38 a.m.
In reply to Recon1342 :
I'll check it when I get back. Regarding the pulley, these engines have an active charging system whereby the computer monitors and adjusts output via a clutched pulley for better battery life and fuel efficiency. The pulley may indeed be the issue; I hope it is, as it's $40 instead of $400+ for the alternator.
