Hi Guys,

I have my 04 Cooper S making a grinding whir sound, BMW service diagnosed the supercharger bearing as being faulty. from the guide on here successfully replaced the supercharger and waterpump however the same noise remains. I have uploaded a quick video with the noise to youtube if you have time to look

You Tube

I suspect maybe idler pulley or pulley belt tensioner could be the culprit? Do you know how I could diagnose further?


I hope I have submitted this thread in the correct spot being a new member, many thanks cheers ...


Your help is appreciated.

Cheers

Davin

 

Buy a cheap stethoscope (like this: http://www.alltradetools.com/catalog...tethoscope.jpg). Almost two months ago I had a grinding sound when coming back from work on the highway. I couldn't tell what it was exactly and I didn't had a stethoscope at home, ended up buying almost the same one as my link and found out it was the alternator going bad. It does look like you have metal dust flying around, so something is eating its bearing. A stethoscope will help you pinpoint what exactly is doing this and will save you money, just don't get it into the strap :p

As a reference, here's a vid of my alternator (bearing in the back was eating itself out):

 

Hi Da Ghost,

Thank you heaps for the reply I will borrow a stethoscope this weekend and check, your noise does sound very close to mine.

One question, do you know if it possible to run the engine with the belt off for 20 seconds or so? Would this cause any problems with computer or idler pulley or timing in anyway? I just thought it would be a good way to determine if it’s something in the engine or not.

Many thanks!!

Cheers

Davin

 

It might not like running without the s/c, never tried, but it's not the best idea, as for the timing, it's not related to the accessory belt, so no. On the other hand, if you remove the belt, you can check the pulleys and see if one of them have some play in it. If you can move it up and down, something is not right.

 

You can run the engine without the belt. I wouldn't do it for long. Remember the water pump is driven off the supercharger. If its nit turning its not cooling. If the noise continues when youbturn the engine off I'd suspect the alternator. Some of them have one way bearings in them to allow the alternator to spin down instead of immediately stopping

 

Hi guys,

just wanted to let you know it was the bearings in the alternator. I turned the engine on without the belt for 15 seconds and confirmed it ran smoothly. all fixed. and thank you all for your help!! many thanks.. cheers

 

Glad to hear you found the issue. How many miles does your car have? On a side note, if a BMW dealer failed to tell the difference between a bad s/c and an alternator, I would stay away from it in the future and find a garage who specialize in german cars.

 

I am 2 years late on this lol but my 2005 mini cooper is making that sound near the alternator like it has a bad bearing. Did you switch out the whole alternator or was it possible to re-insert new bearing? Please let me know!

 

yeah mate i just got a new bearing installed in the alternator for $50. quick and easy.

 

Awesome. Did you get it installed at a local garage?

 

went to a local auto electrician that specializes on fixing alternators. very easy.