Apparently, reman MINI alternators do not exist. Even though RockAuto lists then from three different remanufacturers (AC Delco, Denso, Remy), when they tried to place orders with all three remans, all three said "oops, we don't have any and don't know when we will have any". So back to square one.
That said, I'm having second thoughts about the alternator diagnosis. Why? Because the car only exhibits the behavior when I shift out of park into D or R. That should make no difference to the alternator while still sitting still at idle... but I can turn the vibration on and off at will, simply by moving the shifter. But when I check under the hood with it vibrating, the tensioner is definitely bouncing some, and the noise seems to be emanating from there, even checked with a stethoscope.
It is possible that you have multiple contributing factors. I would still suggest to go to the auto parts store to feel a new alternator so you can determine if yours is abby normal. If it is then you still need to remedy that issue anyway.
It is often difficult to identify issue #2, until issue #1 is resolved.
think of it as a tuning fork. When it's hit near the "natural" frequency, it's amplitude is very high. When hit at a frequncy far from what it likes to ring at, it won't bounce much.
Hmm, that's a tough one. So the vibration only occurs when the driveline is loaded, and it's shaking the engine hard enough to oscillate the tensioner. Check your lower engine mount for tears? Maybe a bent axle? No, the axle's not rotating. Hmm, weird.
Just had the lower mount out this weekend... looks fine.
Yep, only when the driveline is loaded a little, but at low load and low speed. Does it through a range of several hundred RPM (900-1800ish), so it's not like it's doing it at one very specific engine speed. Once I get above "driveway" speed and RPMs, it stops vibrating. Shift into park, stops vibrating. Haven't tried neutral, but will.
Nothing that I can think of changed to coincide with the appearance of the vibration. I changed tranny fluid a couple of weeks before this started. Crank pulley (ATI) has been on for several months. TSW engine mount for a couple of months.
I'm not convinced that there's not an issue with the alternator bearings... but it just seems really weird to me that the symptom is completely dependent on transmission engagement. I suppose that changes drivetrain harmonics a bit as Dr. O suggests and that could be the difference...
Solid advice - my original R53 had the same symptom post tensioner install (and new pulley). Three free tensioners later from the dealer, they opted to try the idler pulley and all was well...
Interesting. I'll try an idler if I can't find another culprit.
For now, seems improved. I installed 17% pulley, brand new tensioner assembly and shorter belt on Saturday. Have only driven it once since... doesn't seem to have the mega vibration like it did - so far.
I also checked all accessories. EVERYTHING was nice and smooth... including my alternator... weird... definitely was not smooth a week or so earlier.
Slightly related topic... for some reason, my car doesn't obey the laws of belt length physics. Everyone seems to say that NAPA 060535 should be plenty short / tight with a 15% pulley and standard size crank pulley. Well, on my car, a new 060535 belt will only show about half a hole in the tensioner. I've confirmed this with multiple belt swaps and tensioners.
But a 060532 is the ticket for me (now with 17%). It's about 8mm shorter and that makes it tight to install, but leaves a whole hole visible when on.
Most folks seem to coach that to ensure no belt slipping, etc. you want to be able to see at least half a hole visible on the tab sticking out through the top of the tensioner. Ideally an entire hole. By the time a 060535 belt gets stretched in a bit, I'm at almost none of the last hole visible.
Is the geometry slightly different for an automatic? Maybe MINI uses the same belt for manuals and automatics and takes up the slack with the tensioner. Weird how the alternator goes from bad to good, too.
This is almost funny - I had similar belt misery amongst diagnosing the idler pulley. I *think* I wound up using the JCW belt from the dealer with my m7 16% reduction, been a while since I dealt with that and I could be mistaken. The NAPA was too short/tight in my setup to jive.
But I'd work on the other trouble more to ensure it doesn't fubar everything and leave you stranded... Like mine did. :crazy:
Noting the tensioner was replaced not too long ago, it probably drops a bit on the suspect list me thinks... Although the PowerFlex rebuild bushings are another great investment.
Here's how mine went down:
Had the m7 16% pulley installed when the accessory belt shredded, just convenient timing kinda' thing. Tensioner replaced under warranty at that time too as it was hosed. Installed NAPA belt recommended for 15% reduction pulley.
Immediately picked up a chatter/rattle on start, especially when cool/cold out. Watched the tensioner bump around a bit, but not wildly so. Noise dissipated after running for a bit.
Noting the action of the tensioner, dealership replaced it thinking maybe the new unit was defective. Same end result.
Changed to tighter belt (recommended NAPA for 17% reduction pulley), thinking maybe the 15% one had too much slack. Good at first. No noise. Then as a few weeks passed, the noise came back.
Acting on a whim after reviewing the shop manual one more time for suspects, I suggested replacing the idler pulley as it was a cheap part and just about the only strong possibility left. Plus when we put ears on the motor, nothing else really seemed to produce the noise (alternator, water pump, etc). Just tensioner chatter.
So, we popped the idler out and found it was hosed via too much wear on the inside allowing movement (felt smooth on hand actuation though). New one installed - all good.
Our theory/summary in the end was the tensioner definitely failed. Idler was on its way, but the subsequent changes to the belts with the new tensioner & SC reduction pulley provided initial tension to smooth over the worn idler movement and make the tensioner move better/smoother/quieter. Then as the belt stretched out a bit, the extra movement would allow the idler to move around and again allow the tensioner movement/noise. The noise on a cold vs. warm start was attributed to simply temperature change effecting the swelling of the belt. Ditto for running, once the belt was up to temp and the idler kinda' got its groove on, then the tensioner would move a little bit but everything seemed pretty decent.
For the record, alternator failures on the MINI are rare according to the mechs here. Not impossible, but almost unheard of...
Obviously your situation may be totally different, but thought I'd detail mine just to add fuel for thought.
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