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-   -   Z4 S54 Rattle... Idler Pulley/water pump? (

elwesso 12-27-2012 10:45 AM

S54 Rattle... Idler Pulley/water pump?
So I recently took delivery of my 07 M coupe.. Car has 49k miles, I believe it's mostly caught up in terms of service but I'm not 100% sure. I'm going to be stopping in at the dealer to pick up my car cover soon, so I'll get a copy of the service records at that time.

On Sunday, I went to take my car out for a sunset drive, and I heard this "rattling" noise...

My first thought was it sounded like some sort of internal engine failure, but as soon as you gave it a tiny bit of gas (say just slightly above idle), the noise went away, which makes me think it was something in the accessory drive. The car runs smooth and strong. I let the car sit overnight, and I took it out again and it didn't make the noise this time. Here's a video of it quiet.

It seemed like I could re-create the rattle whenever I turned the steering wheel to full-lock..

I did my "civic duty" and performed a search, and I ran across this thread:

I listened to the video in post #7 of the water pump impeller noise, and it sounds pretty similar to the nosie I'm experiencing. The problem with it being intermittent is it's tough to diagnose, so I know I need to try and get it to make the noise again, and get out my stethescope to isolate it.

Does anyone have any thoughts on this? I bought the car from a dealer (not a BMW dealer), and it came with a 3mo/3,000mi powertrain warranty. If it's in the water pump or accessory drive, it technically wouldn't be covered but I'm hoping that maybe they cover it since I've literally put 100 miles on the car since I've owned it since last Friday. I want to have an idea on what the issue could potentially be, because worst case scenario I'll replace the parts myself.

I know for sure both drive belts were replaced about a year ago, but no mention of the water pump and/or tensioner.

khammack 12-27-2012 12:19 PM

From the video, it sounds to me like something external to the engine. Maybe like something hitting the fan?

elwesso 12-28-2012 12:55 PM

I didn't see anything interfering with the fan... Any other ideas? I'm going to have the dealer take a listen when I go to pick up my car cover, and I'll report back. They will have to listen to the video as I'm not driving the car today (damn snow)

brock5ga 12-29-2012 03:19 AM

If you can get it to make the noise again as in the first video, remove the belt and see if the noise goes away. You can also remove the belt and rotate all pulleys to check for roughness or binding, also checking side to side play. Also look at the belt tensioner, check it for alignment with the other pulleys. Look at it from the side and make sure it isn't cocked out from wear. If you align all the pulleys with your eye, it should not stick out further than the other pulleys. Also watch it with the engine running for excessive vibration and rattling resulting from a weak spring.

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