Hi, folks. R53 MC40 here. I have an intermittent high-pitched squeak upon start up that goes away after a minute or two of driving. I pulled the passenger-side wheel liner and jacked the car up with the wheels removed. Then I used a mechanic's stethoscope to isolate the squeak. Idler pulley, A/C compressor and crank pulley seem normal. It sounds as though it's coming from the supercharger because when placing the stethoscope tip near the pulley there appears to be more noise than I would think normal. I removed and serviced the S/C and replaced the oil at 125,000 miles (no noise at that time). I'm now at 145,000 miles with said occasional squeak at startup. What I don't understand is why the squeak would be intermittent and then disappear after a minute or two of driving if an S/C bearing was actually bad. I would think the squeak would be continuous. Has anyone else run into a similar issue? If so, other than an S/C rebuild did you find a solution? Thanks.

 

One additional note: After pulling the belt, none of the pulleys make noise when manually turning/pulling them. The S/C pulley when turned does emit a faint engaged gear sound but that would seem to me to be normal.

 

One additional finding: After removing the belt none of the pulleys make noise when manually manipulated save the S/C pulley that makes a faint gear noise that I assume would be normal. No squeaks.

 

I don't know if you ever resolved this, but check out this possibly-relevant bit from the Timing Chain Tensioner part description on Detroit Tuned:

​​​​​​https://www.detroittuned.com/mini-co...ain-tensioner/

​​​​​​​That part of the description was what made me decide not to go that route with the noise my Mini is making. I had my timing chain replaced by a shop when they installed my "new" supercharger and I sincerely hope they did the tensioner too, since they usually come in a kit. But either way, my noise persists and isn't just at startup like you're describing.

Not sure if that's helpful or if you already figured it out. If you did, please update me. Thanks!

 

When you remove the belt, there's no tension on any of the pulleys; they tend to go silent when you remove the tension. Check the pulleys for axial and radial play and rough feel when rotating. With the amount of miles you have on the engine, it may be time for a refresh anyway. You should probably measure the belt tension to make sure the tensioner is servicable.