Hi All , Can anyone help ? When cold there is a rattle on start up which I thought was a loose belt. But on checking all belts were tight. I have since been told it is to do with the air conditioning clutch ! When I start the car cold the rattle is pronounced but after a few minutes it disappears. The initial rattle is getting more severe. Has anyone got any ideas ? Jerry
Hi Jerry, I'm not saying that the problem you have is the same as mine but periodically I get what sounds like an electrical "arcing" noise coming from the alternator area. Turns out that its coming from the alternator drive belt even though it looks ok. To test this, start the car and spray some WD40 directly on the belt - if the noise stops you have your answer. Not necessarily a repair but a quick fix which stops an annoying noise. Looking forward to meeting you at Silverstone in a couple of weeks. Russ.
Using water instead of a spray oil (wd40) might be a better idea. If in fact noise is from belts, first make sure they tensioned to spec. second deglaze using Ajax type material. Apply on pulleys and start car, can take several applications.
Russ I have the same arcing noise around alternators on start up. Local garage said a belt was loose and I did not buy it since tension seemed good. I will take a second look, feel, adjust and/or squirt something. Jerry If AC clutch is causing the rattle you should be able to see it from above (visible on my 400i). Have you adjusted your timing chain per manual? It is a likely start up rattle. Don't leave it unattended to! Ken
I have the same sound and a reputable shop (SportAuto in CT) told me that its common, even with new belts. The sound goes away within minutes.
Ditto +1, the alternator snapping sound is very common & typically goes away after a few minutes...no big deal
Speaking of new alternator belts. Anyone have the gates or napa part numbers for the alt belts? Is it gates 7M560? The other belts are Napa - 25-9295 - 25-9300
The snapping sound I think occurs when the car sits for a while or is not driven regularly. It must be that the belts takes a "set" in the shape that they have been sitting in over a period of time and snaps until the belt loses that set. If you use the car frequently, it doesn't seem to take the set and therefore it doesn't snap on startup.
