My 2001 XJ8 started making a whining noise a couple of days ago. The noise seems to be coming from the right side. Does it worse it seems when you first crank it up. I first suspected the drive belt idler on the right side but when I took the belt off and checked it it seems to be fine, so is the tensioner. Then while working on it it stopped cranking. Voltage low as if alternator wasn't putting out. Voltage check shows it isn't charging. Maybe the alternator is bad and that is where my whine is coming from. But if the alternator stopped charging wouldn't the dash give me some warning of this? This is what is puzzling me. I'm going to pull the alternator tomorrow and check it off the car. Can anyone give me any ideas as to why a didn't get any warning indications on the dash?

 

Did you start the engine cold with the belt off, as I suggested in response to your post on the other thread?

Did you test your battery voltage? It's probably just dead.

Yes the alternator can be the source of your noise, verified in part by running with the belt off. Yes, you will see indications from both the battery warning light and a message like "charging voltage low", or something like that, I don't remember at the moment.

No, running it with no belt will not allow a good battery to discharge: you'd have to run the engine long enough to melt it, as you don't have any coolant circulation with the belt off, either.

 

The battery voltage was about 11 and doesn't go up at all with the engine running at idle. Above about 2000 RPM it rises slightly, so the alternator acts like it is trying to charge. I started it just now with the belt off and the noise is gone. Tensioner, idler, alt all feel like they have good bearings. No indication of anything wrong. Even with the belt off I still didn't get a battery fault indicator on the dash. Removed alternator and it tested bad. It made noise on the test machine. Guess it has to have belt tension and high RPM before it will make the whining noise. Planning to have the alternator rebuilt. Thanks for your advice.