e39 generator issue i cant really explane

symbiontsik · 04-04-2026, 01:38 PM

Hi all,

Its ongoing issue with my friend's car's M57 engine, and the issue started with the belt tensioner making noise when the lights were switched on. A small ticking noise is coming from it, and we have taken the most common way of fixing it by throwing money at it. The water pump was replaced, the belt tensioner was replaced the alternator was replaced. By all this, the result was that charging got better, and we had fewer places to put the blame. Noise now sounds like a chain is stretched. If you remove the belt noise stops. So today we removed the plus cable from the generator and were surprised that the noise stoped but if you just remove the small connector, the noise stays and gets worse when the lights are switched on. So my question here is, have any of you run into something like this.

FoxberryJam · 04-05-2026, 06:35 PM

Quote:

Originally Posted by symbiontsik

Hi all,

Its ongoing issue with my friend's car's M57 engine, and the issue started with the belt tensioner making noise when the lights were switched on. A small ticking noise is coming from it, and we have taken the most common way of fixing it by throwing money at it. The water pump was replaced, the belt tensioner was replaced the alternator was replaced. By all this, the result was that charging got better, and we had fewer places to put the blame. Noise now sounds like a chain is stretched. If you remove the belt noise stops. So today we removed the plus cable from the generator and were surprised that the noise stoped but if you just remove the small connector, the noise stays and gets worse when the lights are switched on. So my question here is, have any of you run into something like this.

I would suggest heading over to the E39 section of Bimmerforums and ask this...

TriumphTim · 04-06-2026, 06:10 AM

Since an E39 probably has high miles, I would check the voltage regulator and its brushes on the back of the alternator.

A brush may be worn or not seated?

04-04-2026, 01:38 PM	#1
symbiontsik Registered 0 Rep 1 Posts Drives: e91 335d Join Date: Apr 2026 Location: finnland iTrader: (0)	e39 generator issue i cant really explane Hi all, Its ongoing issue with my friend's car's M57 engine, and the issue started with the belt tensioner making noise when the lights were switched on. A small ticking noise is coming from it, and we have taken the most common way of fixing it by throwing money at it. The water pump was replaced, the belt tensioner was replaced the alternator was replaced. By all this, the result was that charging got better, and we had fewer places to put the blame. Noise now sounds like a chain is stretched. If you remove the belt noise stops. So today we removed the plus cable from the generator and were surprised that the noise stoped but if you just remove the small connector, the noise stays and gets worse when the lights are switched on. So my question here is, have any of you run into something like this.
	Appreciate 0 Tweet Quote

04-06-2026, 06:10 AM	#3
TriumphTim Private First Class 187 Rep 180 Posts Drives: 2008 328xi Join Date: Dec 2020 Location: Perkasie PA iTrader: (0) Garage List 2014 Tesla Model S P85 [0.00] 1955 Triumph TR2 [0.00] 1988 BMW 325is [0.00] 2008 BMW 328xi [0.00] 2005 BMW 325ic Coupe [0.00]	Since an E39 probably has high miles, I would check the voltage regulator and its brushes on the back of the alternator. A brush may be worn or not seated?
	Appreciate 0 Quote