03 MCS:

I was driving home today, in stop and go traffic with the AC on, and my car was sounding STRANGE. Upon acceleration, a 3-4K rev sounded as if he was at redline: heavy, growly (not necessarily in a good way), loud. So loud, in fact, that the revving sound quickly drowned out the supercharger whine.

I also noticed--and please forgive my lacking powers of mechanical description, here--that the sound seemed as though something was spinning uselessly. Almost as if something was superfluously spinning without tension and in a useless-sounding manner. Not a high pitched whine-y spinning noise, but almost as though the car continued to rev even when I had the clutch in to upshift. Perhaps it would make more sense to say that I did not hear decreasing revs with the clutch engaged for an upshift. Just sounded like something continued to spin/rev.

If it matters to anyone, I've been smelling an intermittant burning smell--relatively infrequently, but too often for me to feel comfortable blaming it on other vehicles. But when I popped the bonnet at the end of the weird-sounding drive, everything under there smelled and looked (superficially) normal.

For as much as I whine about my car, the overwhelming majority of issues with him have been computer-related. This one definitely sounds mechanical in nature and it's kind of freaking me out. I'm not asking for an internet diagnosis (have to take him to the shop to hopefully resolve some of the aformentioned computer glitches, anyway) I was just wondering if anyone had experienced anything similar-sounding.

 

I'll bet the sound goes away immediately when you turn off the AC while you are revving.

Mine is like that also.

I got a call from MINIUSA after i posted about the awful noise, and theye were, shall we say, less than useful?

I asked why they were calling and they said they had seen a posting about my noisy AC while revving.

I asked what they knew about the problem, and they said, "Oh, I've never heard of it"

I asked what to do about it and they said to take it to the dealer.

I asked why they called if they were going to be 100% useless (not really) and they said it was just a "courtesy" call.

Sheesh. It sounded a little like a warning not to post problems, because "They are WATCHING!!!"

 

It could also be a bad bearing in one the pulleys the belt is riding on.

 

Omtoast,

I think Trippy is right. Turn off the AC while you have the revs up, and the sound will stop. This is evidently a very common problem. I have it and had posted a question just a couple of weeks ago asking if a fix had been found.

I did some research (not on NAM or MINI2) and found that another car had a similar problem. It was caused by a harmonic resonance and the solution was to slightly deform a hose by clamping it and hanging a weight off of it. It could be something similar with our MINI's. It seems to do it only on hot days in my car, which makes me wonder if it has something to do with frost forming on a hose.

Any any case, it's a pain. On my commute home, I encounter stop and go traffic, and I often leave the MINI in 1st and let the revs get up to about 3500 before shifting, and the "wahhhhh" growl is very annoying.

 

The sound you hear is the pulsations in the refrigerant lines caused by the compressor. It's not always repeatable, and is most common in hot weather while driving in traffic or side streets. The pressures in the a/c system increase in such conditions, and this makes the 'drone' from the compressor more pronounced. Nothing here is at risk of being damaged, it's just a quirk in the design of the car which has such short runs of refrigerant line between the cabin and the compressor. Longer runs tend to act like mufflers, and actual 'mufflers' are sometimes designed into an a/c system to combat this phenomenon. There is not much room to incorporate typical mufflers in the MINI system (most are the size of 'Red Bull'-style beverage cans).

I've gotten kinda used to the sound.

 

I have the same whine and, as Trippy says, it happens ONLY with the A/C on.

 

Thanks for all the info

I hadn't ever noticed such a noise with the AC before, but then I actually use my AC VERY infrequently. In fact, the only time I've used it extensively was on my road trip and that was all freeway driving.

So... good to know. I've climbed down from the ceiling now, and I promise to stop making silly threats that if my car doesn't shape up, he'll be a Prius before the month is out.

 

Well... haven't had the AC on the past 2 days since the weird droning and I think he sounds fine. I'm tempted to say that he's still mildly droney, but I'm about 98% certain that that's me being paranoid.

Thanks for all the help

 

Boy thats a lot of mods to change your MINI into a Prius

 

^^

I promise to list them mods if I ever install them--just in case anyone esle would like to power upgrade to a hybrid!