Can I ask a BMW question ??
 

A good friend of my wife and I has a 128 (2012), I always change her oil for her as she is a very good friend. Her car has 80K miles and has a horrible squeal when running, I though not too hard so I installed new Gates Idler pulley and tensioner pulley...same squeal. It does not change with the AC on or off...so I am thinking alternator ??

Not much else except the water pump and not a leak from that. I put a large screwdriver against the alternator casing and put that against my ear and I can hear a rough sound as the car is running but not the squeal through the screwdriver....but you can sure hear it outside....any thought ....alternator is pricey and I am trying to help her out.

Thanks

Dwight

Get a stethoscope and locate the squeal. You should confine yourself to the act of "throwing parts" at a problem to when a problem is intermittent. If the squeal is constant it should be verifiable.

Take thw belt off and see if you still hear the squeel

If no squeel spin each pulley one at a time until you find the faultybearing

HF stethoscope is less than $5 and they work great. +1 on pulling the belt and checking each rotational part. Also put a meter on the system and see if it is charging correctly. If the alternator is failing, it might show up as lower voltage?

epiphany
 

I hadn't thought about the alternator clutch pulley....I was thinking of old school direct drive alternator.

And yes 13.8 to 13.9 volts with the headlight on high beam at the battery....it has to be just mechanical

You replaced the tensioner but did you do the belt? Once a belt is stretched out it won't be good. Go with a decent belt if you haven't done so, don't get the cheapy from Auto Zone.

Hmmm, I thought this post was about something sexual, with all the talk about a Very good she Friend, always changing her oil, playing doctor with a stethoscope and all the squealing going on.

Are we sure this is even a car problem :p

Perhaps less Viagra might help reduce the squealing.

Whats viagra ??
 

Seriously, this lady is like my little sister (Insert Southern Jokes here)

Well I got the alternator off and it is smooth as glass, took it to Oriley's for a spin test and no noise at all....it did fail the Lamp test however ??? whatever that is....the output was 13.89 volts....I guess a new Gates belt is next and see what happens...the water pump is smooth also and no wobble or leaks....this is getting frustrating