525i engine noise

My 1995 525i has 300k miles and still runs great. Recently the car in making a constant "thumping" noise. I have isolated it to the engine, but have no idea what could be and it has not impacted performance.

Originally Posted by ecullen

My 1995 525i has 300k miles and still runs great. Recently the car in making a constant "thumping" noise. I have isolated it to the engine, but have no idea what could be and it has not impacted performance.

Can you post a video of it? Sounds are very hard to diagnose over the net without a video. We'll need more details as well.

Does it do it when driving or can you hear it when the car is stationary? Does the frequency of the noise vary with engine RPM?

Video will be posted next. Yes it is tied to rpm and it can be heard when stationary.

The video of the noise is posted to YouTube..."Mystery noise 1995 BMW"...i cannot upload to this site.

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Originally Posted by ecullen

The video of the noise is posted to YouTube..."Mystery noise 1995 BMW"...i cannot upload to this site.

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I just looked for the video and couldn't find it. Can you post the link?

Sounds like a cracked pulley on a belt driven item.

hopefully ,maybe the fan hitting the shroud.Ill agree maybe a bad fan pulley: ?

Agree with the above two, but its kinda hard to tell with the hood closed. ecullen, is it possible for you to take a vid with the hood open and try to aim the camera where the noise seems to be coming from? There's a lot going on under the hood that could be causing the noise.

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Originally Posted by ecullen

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Well, I could not see the video link in your post above. I was only able to see the link by clicking to quote you.

Anyway, I know this will sound crazy, but you need to check to make sure that your spark plugs are tight. I have seen vids of the same sound and the problem was a loose spark plug.

Hope this helps and let us know.

PS: It still doesn't show up for some reason, so here is the link for others to watch:

Thanks I will check everything you suggested. And listening to some YouTube videos it sounds very much like the vanos pistons but that's the last thing I will check.

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Sounds are particularly difficult to diagnose when you are not in front of the car and able to look see, play with the throttle, etc. You should take your ride to a mechanic. He would have narrowed it down within 5 minutes considering how loud it is. Sometimes its just more efficient to pay the fee and make progress on the resolution. And you run the risk of something snapping each day that you delay and guess at it. Just imagine if it is indeed a cracked pulley like what bmwff (the last best dude to join these forums) suggested. Not worth saving $50 over.