Hi,

Recently (past month-ish) my R53 squeals like a pig around 5k rpm (give or take) but only under load (basically flooring it).

When it first happened, I assumed it was the belt, and had that changed. Nope, still happening.

So I'm looking for opinions. It really sounds like the belt, but the belt does not show signs of slipping. Also, if I just rev it up (not under load, so, revving while stopped) she revs all the way to redline with no squeal.

Some information that may be helpful. Car has 15% alta pulley (not sure which version EDIT: This is the Alta V2), alta tension stop, GSR intercooler, miltek exhaust, has a tune.. not sure which as it was done by PO, and close to 80k miles.

I feel like I'm barking up the wrong tree, but could it be the clutch?

Thanks for the help.

-JM

 

Generally speaking if it was the Clutch...I would expect the clutch to slip under load (when it is squealing) easy test, find a hill, floor it feel the car accelerate and when the squealing starts does it feel like the clutch is slipping.

If it were the Belt, ...you changed the belt so it the old one been glazed and squealing the new one would have ending the issue.

Then there is the wonderful Crank Pulley With Dampener, when it starts to go, it may be shot, but still functioning well for the most part, but under load it slips and squeals like you described...(my money is on this is your cause)

So the next possibility is Hydraulic Belt Tensioner... when the bearing starts to go out it can cause some squealing...

...and the one we only whisper in fear that it is true... Supercharger... but I would bet dollar to donuts it is the Crank Pulley With Dampener.

Best of luck.

Motor on!

 

check the alta pulley . the bolts come loose and they pulley walks off or spins. You should be able to get an allen wrench on it without jacking the engine up.

 

WHICH belt are you using....
Just the fact it is new does not guarantee it fits right....
The squeeling at 5k+ under load seems consistent with belt noise...too long or misalignmented...
DO check the pulley is tight...if it is loose and the bolts not locktighted, it could destroy the shaft pretty fast....still have the OEM damper...a aftermarket damper installed wrong could slip...destroying the end if the crankshaft..similar noise...

 

If the crank pulley is slipping you'll throw a code and go into limp.

Verify your belt length. Should be 535 or 532. On the belt tensioner, how many holes can you see on the gauge.

Does it only do it at 5k? Does it stop after that or do you shift at 5k? What if you ease it up to 6k then hammer it, does it squeal?

Do you feel any difference in the power when it starts making noise?

 

Dropped the car off with my trusted MINI/BMW mechanic (not stealership, just trusted mechanic). He had the car for a day, and was able to reproduce the sound.

he says:
it does NOT sound like a belt
There is NO EVIDENCE of slipping
The tensioners and dampers Appear healthy and functional

It DOES sound like it may be coming from the by pass valve. The valve is set for a certain amount of boost, and with the reduced pulley, and my driving, this could make sense.

So, NAM... thoughts? Time to up the by-pass valve?

 

It would take a mechanic 10 seconds to zip tie the valve open or shut to test his theroy....
Surprising he did not...

 

ZippyNH,

Thanks... I'll give this a shot!

-JM

 

Also, I took a video of it (just for the sound, mind you, as the video is just of the tach), if anyone wants to hear.

Listening to the video, it's clearly NOT the belt, but more a whoosh of air, like a big turbo... which is weird (R53, definitely not turbo).

 

wonder if your intercooler boots are leaking or cracked....they are rubber....and after about 5-8 years....they DO crack....bet the air diverter might be deflecting the sound....

 

Boots are definitely a possibility, I can take a look there after I close the BPV.

No stock diverter though, PO installed a giant GSR intercooler.

 

Both of my 05 MCS's do this under load. I believe it's the BPV. Is it normal or should I replace the valve?

 

Did you ever find out what specifically was causing this issue? I have almost the exact thing occurring, trying to diagnose now. thanks.