I wanted to see if there are any mechanics out there that could give some input. I have a 2008 XJ and a couple of weeks ago I started the car and heard a whining noise coming from the usual area around the belts. It seemed to be the loudest when I first started the car and as I drove and picked up speed you didn't hear it as much, or at all, but when I stopped at a light you would hear it again. The strange thing is that after doing this for a few days it mysteriously stopped and was normal, for maybe a week, and then it started doing it again, and still is doing it. Now, I had a new water pump put on last November, so just about a year ago, so I guess I can rule that out, unless it failed, but I'm not having any trouble with overheating or anything. What else could it be, a power steering pump? Or someone told me it may just be the belt, which I never understood why a belt would make that noise, but looking at my belt, it seems to look good. Any suggestions?

 

Take the belt off and start the engine. If noise is gone replace belt and/or idlers and tensioners.
Yes belts are a wear item and do make noise.

I would have put a new belt on when the water pump was changed. Why do the labor to re-install an old belt?
Can you DIY anything?
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If you took belt out, see if you have any glazed spots on surface that face pulleys?
If you did take it out just put new in, don't mess with stuff below
If you haven't took it out, you can try one of these:
If this is belt, those sprays will give some time, but will not fix the root cause: you will have to replace belt.

 

You could try the old bar of soap trick to see if your belt is the noise.
Find a place you can touch the belt to see if noise stops

 

The other thing that can cause a whine is when the aircon refrigerant is low. I had a small whine on both of my X350s and they were cured when i had the air con serviced, which includes replacing the refrigerant.

 

My first thought was that the alternator bearing could be going out. I mean, that was quite common in the earlier vehicles.

 

Thanks, Did the whine occur when the air was on only, or when it was not on as well? Because I haven't had my air on for a few weeks now.

 

Try the old screwdriver stethoscope trick. With the motor running, and carefully…get a long screw driver. Put the tip end against the various components..and the handle end against your ear. That will help isolate the culprit.

 

Well, today all of a sudden, my battery warning light came on when I started the car. I just got a new battery about two months ago, so I don't think it's that. So, it is probably the alternator. My question now is could that have been the alternator that's making the whining sound? I just dropped it off at the shop so they are going to check the alternator and replace it if it's bad, so I'm hoping that maybe that is where the sound was coming from.

 

Yes, that might be possible, in two ways:
one, the alternator itself makes the noise, for whatever reason
two, the alternator puts a higher resistance on the belt and thus makes the belt do the whining noise

Best regards,

Thomas

 

Hi D.C. - did this turn out to be the alternator? My 2007 XJR has something very similar...intermittent whining / whirring noise, followed a few days later with charge system warning light and cessation of the noise! Belt was replaced last year, but I'm suspecting alternator has failed on mine.

 

Jeff, sorry for the delay in answering, I haven't checked on here in a while. Yes, it was my alternator. After changing it the noise was no longer there.