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Need help with noise from bmw 1series 120d 2007

hello everyone,
i am new to the whole forums so please correct me if i am in the wrong place. or written question wrong.

so basically i need some help from a knowledgable person / mechanic to advise me on a noise that is coming from my engine on low idle,

i can upload a video. towards the end of the video you hear it more clearly,
i have just replaced crankshaft pulley and belt.

please help me locate the problem. thank you

** UPDATE **


I appreciate all the help guys

Well tell us about why you believe this repair was needed… how the repair went… and how this noise manifested itself.

Tell us a story, we love stories. And a story with a video ia about the best you can do to convey the issue.

There are a great many knowledgeable people here who can assist you depending upon the stars alignment, we might even get it right. So tell us the story

We will certainly try… but noises don’t record so well and 2 experienced ears close to the car can tell so much more. An actual mechanic might be a more cost effective way to get this fixed in the long run.


hello thanks for the reply,
i was certainly thinking that myself. i was just taking a gamble to see maybe just maybe it could be hesrd and diagnosed without paying lots for a mechanic to pop out to me because of the current crisis moneys not so great, so where i can save a few pounds is vital.

here is a link to the video.

please if you can have a listen you might be able to hear it. more so towards the end of the vid

Oh and +3 to what @Mustangman just said.

hello, cheers for replying.

basically my crankshaft pulley had burned down, basically lots of rubber melted off of it, i caught it before the belt had actually broken so pretty certain it did not cause any further damage. anyway i had the car sitting for a while. maybe a year due to bad health, i finally got round to fixing the pulley, installed new one, torque it down, put new belt on, but this is when the issue with the noise has arrived.

here is a link to the video,

please if you can listen closely, i believe you may be able to hear it clearly towards the end of the video
thanks for your help

Ok yes it is going to be hard for us to do this remotely. To me…and from here it seems to be running smoothly but has a sort of “Hollowness” to the sound if that means anything. I think i can hear it.

But again… please tell us the story… i wasnt kidding.

Was this the same sound that made you suspect and replace the main pulley? Why did you do that repair… was the noise different after the repair? Did anything occur after the repair or did it get worse.

How did you remove the main pulley and damper and how did you replace it?

Tell us the entire story… we need it to assist.


Very subtle noise. Sounds like an exhaust resonance to me. Sounds like nothing serious to worry about but the story would help a lot.

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i understand you sir.

loud and clear.

so i was driving down my local shop, when i noticed a smell of like burning rubber, i pulled over and noticed there was bits of rubber hanging of the main pulley, the belt was still intact, but did need replacing. i drove straight home 1 min away, and parked up since.

yes the noise is different. tbh there wasnt any noise when the pulley was broken. just the smell of burning rubber. so the noise is definitely different now since fixing.

i removed the main pulley by putting it into gear 6 and used a breaker to undo it. was a few parts i had to take of the car to get to it thought. eg the fan, and filter and box.

i just had a mot and he did say there is a slight bit of play in the wishbone, and front suspension needs looking at,
could that be the reason for the noise?

im assuming its more engine related but i could be completely wrong.

thats what my dad had said to, so possibly something to do with the exhaust?
the car is running very smoothly, drives perfectly.
no warning lights nothing.

Sure sounds like that. Very subtle, as I said. You might be a bit sensitive at this point. It may have made that noise before, you just never noticed it. You just fixed the car so now you are hearing EVERYthing that might be a problem with the car. Sort of like Lewis Hamilton on the last lap of a race when he’s leading by 2 car lengths… he’s noticing anything and everything that might spoil the win.

I wouldn’t worry about. If there is something failing in the exhaust, you will hear more noise or notice it hanging lower from a broken hanger.


What you might be hearing is the way it is supposed to sound.

If your previous damper had bits of rubber coming out if it… that rubber is what the outer ring weight of the damper floats upon… and if your previous one was so soft and degraded that it was coming apart… you may have become accustomed to how it was NOT supposed to sound and behave.

Everything seemed smooth to me the steering wheel was not vibrating at all and it seemed like no secondary vibes were being transmitted through the vehicle but only you can tell us that for sure…

Now that the main pulley is new and the rubber damper is also new… you just may be hearing your auto tensioner on the serp belt moving around as it was designed to do ( the hollow sound i mentioned)

With the old degraded damper it would put less strain on the tensioner bec the damper was so soft…and now with a new damper the auto tensioner moves a great deal… as its designed to do.

Unless you are feeling vibrations in the wheel or your pedals etc… you are in good shape.

Also… with the engine running open your hood and watch your serp belt and look at the main pulley… if the main pulley is wobbling that is a problem… if it looks like it is standing still while its actually spinning at 800-1000 rpm’s then it is running “true” and there would be nothing to worry about at that point. Rev the engine while you are looking at the main pulley… or have an assistant rev the engine a bit for you. Take a look and report or post that video

That main pulley should look like its standing still while its spinning… no wobbles is what you want…and if that is what you have, you and the engine are in fine shape.

I don’t think it is your belt. If the car has been sitting for a year or so there is a good chance that your oil filter has dried out. If it did than most likely the paper folds of the filter have collapsed. When this happens the noise of the rushing oil within the filter housing is making exactly the sound that your car is making.

After a year of not driving it would be time anyway to change the oil and filter.

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Who suggested the belt was the culprit @kurtwm1 ? The belt is what you need to look at to verify that the main damper pulley is in perfect alignment. One needs to look at the actual damper while its spinning… and also look at the belt as a tell tale of the dampers balance condition.

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hello cheers for the reply,
i shall change the oil filter soon as, along with the oil. thought to be fair 2 days before it broke down a year ago, i changed the oil and filter. so technically its new.but can change anyway.

cheers for replying. im going to show a vid of the whole engine tomorrow

i will upload a video tomorrow of the whole engine, so you can examine the belts and pulleys for me. hopefully we can find the problen together.

thank you for helping

My focus would be on the main damper. Whatever video you provide try to get some video of up underneath so we can get a proper look at that main pulley… while its in motion

It needs to look like its standing still while its spinning at idle and above… no deflection is acceptable…not there.

…and of course from the top down also… so we can view the accessories as well

Basically the view as youre standing with the hood open looking at the engine, the belt and its accessories in motion… and then underneath looking directly at the main damper…

Good luck

Honestly, I don’t hear anything, but having put over a million collective miles on my various small BMWs, I can share the things that generated odd noises from my BMWs:

  1. Worn idler pulley or tensioner pulley bearings.
  2. Worn tensioner assembly.
  3. Loose heat shield on exhaust manifold (rivets got loose. I patched up with high temp JB Weld)
  4. Missing plastic covers beneath the engine
  5. Loose heat shield on frame next to catalytic converter
  6. Failed air injection system check valve in exhaust manifold