I have the same problem on my 323i (2000 model with 84k). I hear this grinding noise when the RPM is between 2000 to 3000 level. This problem showed up after the dealer fixed the AC problem in my car. At first it was a loud rattling noise which occured at 35~40mph. The dealer then changed the AC compressor & the belt tensioner to fix the rattling noise, but now I am stuck with this grinding noise which occurs only when the rpm is between 2000 and 3000. The noise stops when the speed reaches 50mph or more.

My friend mentioned that the plastic cover on top of the engine could be vibrating to produce that grinding noise. He suggests inserting some insulation between the plastic cover and metal part. I haven’t tried this out yet. He also suggests replacing the belts (which are little worn out)

• Grinding Noise at Cold Start-Ups - halmkim 2005-12-18 00:22:14 (891 views)
  • This happened with the Ex's 323. I replaced the tensioners - bimmer5michael 2006-03-04 07:55:11 (506 views)
  • From where does the sound originate? The engine, the transmission, rear end? - davidc 2005-12-18 16:31:51 (632 views)
    • Re: From where does the sound originate? The engine, the transmission, rear end? - halmkim 2005-12-18 17:17:40 (646 views)
      • My first guess would be the water pump. Any signs of coolant loss? - davidc 2005-12-19 00:33:38 (705 views)
        • Re: My first guess would be the water pump. Any signs of coolant loss? - halmkim 2005-12-19 08:22:00 (643 views)
          • could be the belt tensioner or idler...also, it could - chip h 2005-12-21 10:44:49 (638 views)
            • Re: could be the belt tensioner or idler...also, it could - carrollf 2006-03-02 04:40:45 (578 views)
              • Re: could be the belt tensioner or idler...also, it could - pselva 2006-06-13 10:19:15 (338 views)