Scream at 4900rpm?

Mr Hardware · 13-09-2013, 12:57 PM

Hey All,

So my AU2 has developed a bit of a scream/whine sound at about the 4800-4900rpm mark. It's not there at 4600rpm and its gone again by 5100rpm or so.

So if i'm pulling through first, it's present on the way up and then again briefly on the lop back down to second under WOT, but only in that narrow rev range. I have no idea what it could be, I have not made any changes to the car in several, several thousand kays. It's just a stock AU2 I6 Auto on factory dual fuel.

Any ideas?

anto · 13-09-2013, 01:19 PM

Long shot but maybe fan belts slipping ?

Maka · 13-09-2013, 07:45 PM

If not what anto said, could be one of the pulley /alternator bearings getting dry? Nothing too serious hopefully.

cheers, Maka

Mr Hardware · 13-09-2013, 08:29 PM

Yeah its more of a scream or a whine than belt squeal

But yeah maka i suppose it could be a pulley, hmmm

what would I do to go about fixing that? could i lube something? what and with what?

Maka · 14-09-2013, 08:34 AM

Are the pulleys still stock? Depending on age they might all need changing. Lube (wd40, silicon spray) one pulley at a time, take for a drive, listen if the noise stopped, if so, thats the pulley to replace > once the pulley starts making a noise its on its way out (when new, bearing is prepacked with grease).

You can visually inspect also, give the pulleys a bit of a wriggle & see if theres any slack or movement, that could point to that one making the noise. Leave the tensioner & alternator bearings till last (most expensive) If it turns out its the alternator bearing, it can be replaced if your handy or take it down to a local mechanic for him to do.

Not sure if you can replace the tensioner bearing, might need to replace the whole unit. If you purchase any pulleys, make sure its good quality nothing too cheap (crappy bearings in em).

For piece of mind, check your harmonic balancer also while your there. Good luck with it Mr Hardware!

cheers, Maka

Mr Hardware · 14-09-2013, 09:09 PM

Thanks for the ideas and information Maka. The origins of the pulleys etc are largely unknown, the main idler was replaced with a unit from Coventry about six years ago, the alternator same story, the power steer pump was a reco probably a bitza from an EL a long time ago, the air con compressor was replaced in 09 and the water pump and harmonic balancer have not been touched in my reign of ownership (more than half the car's life!).

Putting all that down on paper it's actually a wonder i've not had problems sooner!
I'll have a stab at a few things and hopefully i'll be able to track it down. Would have been a bit easier if it was at 900rpm not 4900rpm....

Maka · 15-09-2013, 10:26 AM

Its kind of well known that a faulty harmonic balancer will show it self at high rpm, thinking about it last night i believe you need to cross this one of the list first, better to be safe than sorry lol! Check your timing to confirm the HB condition (if timing off either way its stuffed).

cheers, Maka