My '08 MCS w/JCW Tuning kit has begun making an odd sound when the engine is under negative load... aka when "engine braking." The noise does not exist when the engine is accelerating, only when decelerating.

It's a squeaky kind of sound, almost like an amplified sound of a CD or DVD drive reading from a disc. It reminds me of a similar sound I had with an old VW bug which ended up being a squeaky speedometer cable, and of a somewhat different sound the vacuum-driven MPG gauge in my old E46 330 made.

I'm under the impression there are no mechanical spinning cables in this car, though, so I don't think that's the issue. I'm wondering if it's a sign of an upcoming turbo issue (wastegate?) or something similar... but the engine has thrown no codes, no CEL/SES.

My car's out of warranty (66K miles). Any words of wisdom before I take it to the dealer for expensive diagnosis?

TIA!

 

My guess would be that the noise is your clutch pleading for mercy. Engine braking is all well and good, but you're making a single clutch do the work of four brakes that are designed for the purpose, and this could easily be causing excessive wear or damage to the clutch.

Spridget

 

Must say that was my first guess too - and that assumes you are doing a really good rev match as you down shift and not relying on the syncros and the clutch to absorb the engagement cuz if you ain't real good at that, then an even MORE agree.

Heel and toe baby . . .

 

Thanks, but my clutch is fine. There's nothing detrimental done to the clutch by taking your foot off the gas, or simply downshifting. And yes, I heel-and-toe downshift the vast majority of the time.

Dealer's shop foreman took a ride with me, and is convinced it's nothing to worry about, just an interior squeak/rattle triggered by chassis flex, and probably exacerbated by the cold temps.

I find it really annoying, but fear if I start paying them $120/hr. to take stuff apart and find it, I'll just end up with more loose pieces and more noises, and a lot lighter in the wallet. :(

 

No kidding? MINIs are noted for their rigid unibody. Odd he'd say that, I wouldn't have expected any flex at all. Although having said that, I wonder if the sound is coming from your engine mounts as they absorb opposite forces during deceleration.

Whew. I retract what I said earlier. Sounds like you know what you're doing!

Cheers,

Spridget

 

It turns out joe shop foreman was wrong... I pinpointed the squeak. And it's a weird one.

There's a vent hose on the engine that goes from the heads down to the crankcase. The fitting where it attaches to the head cover is a plastic "snap into place" little doohicky. Apparently, it's decided to get vocal. When the engine torques and shifts a little under acceleration, the squeaky fitting shuts up.

For testing only, I used a velcro strap to pull the hose tight... using the large air hose (that leads to the intercooler, I think?) as a support. This limited the motion of the fitting, and the noise went away on a test drive.

I tried all manner of lithium grease, oil, even BMW Gummipflege, to try and lubricate the squeak away from the fitting, but none of those worked. So I either have to just stick with my hack-job velcro repair, or find out from the dealer what it will take to replace that fitting. I suspect the whole hose will have to be replaced, and that they'll charge me an hour of labor as well. :(