My 2005 MCS has developed a rattle around 2k-3k rpm, I'm not sure exactly where it's coming from but it's very obvious, it almost sounds like I'm grinding gears or parts are spinning through gravel or stones. I took a video of it at very low speeds so it can be heard better: https://drive.google.com/file/d/1OH4...ew?usp=sharing

The rattle seems the most obvious when I let off the gas pedal between 2k and 3k rpm, and seems to disappear entirely over 3000. The rattle stays even when the clutch is pushed in, or the transmission is in neutral. I had the harmonic balancer replaced recently and the supercharger rebuilt, the car has 68k miles on it right now. Any ideas as to what the problem is? Should I stop driving it until its fixed? I don't have an immediate need to drive anywhere, given conditions right now. I'd appreciate any help on this, thanks!

 

It's kind of hard to hear the rattling in the video. Does it make it even when the car is not moving and you increase RPM? I would try to pinpoint where the noise is coming from on either side of the engine bay. It could also help to possibly run the car for a few seconds without the drive belt attached (just for a few seconds when the car is cold to avoid overheating) and see if the noise is still there. It could potentially be a few different sources but its difficult to tell without some more investigating.

 

Not picking it up on the video, sorry.
Is there any vibration with the rattle?
So far its independant of RMP's correct so not a rotational rattle comonsurate with throttle application correct ?.

 

Before you throw money at it, check the bushings on the belt tensioner damper (looks like a small black hood lift). It's a common problem with older Minis for the bushings to dry out, fall out and create metal to metal vibration with the two attachment bolts. Take your front right wheel and fender liner off and it's right in front of you. It's a cheap fix ($16) and only takes 30 minutes to install.

 

Sorry, I realize now that google drive compresses the audio a bit and makes it hard to hear. :( Yes, it makes the sound when the engine is not moving, and it's always between 2k-3k rpm. Is there an easy way to remove the drive belt? I don't have too many tools with me right now.

 

No vibration, sorry what's RMP? The rattle is more pronounced when I lift off the gas between 2k-3k rpm.

 

bump

 

Did you ever figure out what was causing your noise? I came across this thread while tying to diagnose my own noise. This sounds very similar.

 

Yes! I replaced the idler pulley and belt tensioner and the sound went away.

 

Thanks. I was kinda hoping it was just going to be loose heat shield! Oh well.

 

Still could be that, or this, as it was in my case once. To me it sounded like bb's rattling in a coffee can:
Price is now up to $20 with inflation but still a bargain compared to the whole tensioner:
https://www.rockauto.com/en/catalog/...r+damper,11663

 

The belt tensioner and idler pulley aren't hard to do at all and not super expensive either. Don't be worried if it ends up being the problem

 

Mine started making this same sound after tightening the belt. I would describe it as a rotational rattle or bearing noise. Mine is only doing it at idle or light load (like backing out of the garage) or moving forward slightly. Any actual load and the noise is gone. Reason I wanted to mention this is because I have an adjustable rod in place of the little shock that is usually on these tensioners. I am thinking this is one of the pulleys bearings that are close to failing and the extra pressure from tightening the belt made this apparent. I will try getting a video of the noise as well.

 

Any update/were you able to get a video? I just replaced my crank pulley with a PRW fluid filled and now notice a noise very low in the rpm range. Can hear a little rattle at like 1k rpm and then is gone by 2k.

 

It may very well be your belt tensioner.
If you can have a look at it when you first start the car when it's cold, (e.g: the engine first idles above 1k - 900 rpms) you may be able to see it "chattering"/hear it making noise.
If not - it might be your idler pulley going bad.
Mine almost sounded like a supercharger whine before it finally detonated...

 

Would swap this out with a factory style dampener listed above and see if that clears up the sound. Mixed reviews / experiences with the adustable rod on this site, would research and proceed with caution in continuing to use one.
+1 and would check all the pulleys with belt removed for binding / bearing noise, excess axial (runout) and radial play, and reverify crankshaft pulley bolt is tightened to the specified torque, 85 ft-lbs / 115 NM.

 

Just my two cents:
1. Check that the tensioner pulley assembly is secured. I once had the long bolt that threads into the SC start backing out and it caused some rattling.
2. Check the tensioner pulley assembly while the car is running. It should look pretty solid. if the pulley is bouncing around that is no bueno. (also a tech tip: if you need one don't buy the cheap ebay special. I purchased one and it was garbage almost immediately. I had to bite the bullet and spend the money so I went with FCP for the lifetime warranty.
2.5. Have you confirmed you have the correct size belt for the tensioner?
3. timing chain tensioner- has it been replaced? If not, it's cheap insurance and easy to replace
4. Because I'm a weirdo, I would also pull the SC. I know you said it was rebuilt recently however, are YOU sure there's enough fluid? Maybe there is too much? Just a thought. It's not hard to do and just good peace of mind - as it's one of the more expensive pieces to replace if it goes bad.

 

I tried getting a video but the noise didn't come through on it as well as I would have liked. However, I did some stethoscoping and I do believe it is from the tensioner idler. Mine does not have excessive movement and it is also worth noting that I have an adjustable rod in place of the little shock.



This was in place when I bought the car and I have not experienced one with the shock installed. If I am not mistaken, I think the small shock is what fails on these and causes catastrophic damage to everything around it, so I should be safe there at least. The potential downside is that I have to tighten the belt quite a bit to prevent slippage under moderate accel with this configuration, which would also put more strain on the pulley bearing. I assume that the standard setup on these tensions the belt under accel in the same conditions.

My plan is to replace this pulley, or the tensioner assembly and check it again.

 

When the tensioner damper on my car failed (twice now) it's the rubber bushings that came apart either from dry rot, oil, fatigue or all the above. In the first instance one of them was completely gone, the other nearly so. I got that 'bb's in a coffee can' sound at idle as the giveaway. Recently I heard other belt-speed related noise at idle and while replacing the belt confirmed the bearings were wearing / worn out on the tensioner pulley and idler pulley (noise, play, and some internal crunch vibration while spinning by hand). Those are both getting replaced this week so the car will be starting with a new damper yet again.