Volvo C70 2.0d strange engine whine noise

[BertoneP]

Hi,
I have a 2008 Volvo C70 2.0d 136 BHP that now suddenly makes a whining engine noise when accelerating.

The car runs fine otherwise and has lots of power and revs without any hesitation.
The car has 117.000 kms on the odometer and I have not changed the timing belt , waterpump nor tensioners etc. yet.

Have removed the oil cap to rule out PCV suction noise...so no issue there I think. Also tried to check the upper intake plastic piping parts but they seem look fine without any cracks...

Could it be the bearing from the alternator or a tensioner bearing ?

Here is a video on the noise: https://www.youtube.com/embed/gby3FEZbtlI
Any clues ????

Thanks for you help !

[lordbasil]

fan belt slipping/squealing??

[BertoneP]

It's more of a whining noise rather than squeaking noise...

I'm inclined to think it's an alternator bad bearing noise.

[dingov70]

Remove auxillary belt & run engine for a short while , if the whirring still occurs change cam belt & idler / tensioners ASAP and possibly water pump as well .

If the noise has stopped , spin one thing driven by the aux belt at a time feeling for roughness & listening for any noise or movement other than rotation from a bearing

[BertoneP]

Thanks for the tip. But if I run the engine without the aux belt on, will that trigger any fault code on the dash ? And is it safe to do so?

[dingov70]

You can run without an aux belt as it only turns alternator , air con pump & possibly power steering pump , so it will not trigger a malfunction light and YES it is perfectly safe . I do it quite often for just the reason you have enquired , it is a quick & easy method of eliminating potential problem area's

[BertoneP]

Hi again,
I managed to remove the alternator and I have noticed that the round metal pulley driven by the belt is "loose" against the rotor inside the alternator...let me try to explain more: if I turn the pulley by hand fast enough the rotation movement is not transferred to the rotor...in fact I can stop the rotor (holding it with a screwdriver to the metal sheet I guess it is to cool down the altermator) and the pulley rotates freely with the force of my hand while the rotor does not.

So definitively something strange going on....perhaps it is as simple as tightening the pulley to the rotor ????

[dingov70]

That would be my first thing to do definitely , I always tell people to start simple & work logically , before hurling money & parts at the issue .

Well done & good luck

[BertoneP]

Did some more testing and reading..so a correct alternator pulley should slip if rotated counter clockwise and not slip if rotated clockwise....just like mine does...so pulley is ok...however if I rotate the pulley clockwise and suddenly stop, the rotor does 1 or 2 turns (which is normal due to the inertia of the rotor) BUT I can hear a slight grinding bearing noise.

According to a Gates video, this is a sign of a bad alternator....

Conclusion at this point: I think my alternator has some bad bearings that generate the whining noise.

Special tools are needed to loosen the pulley bolt to be able to replace the 2? bearings, so I will just buy a new alternator and a new tensioner (while I'm at it) to see if this fixes the problem. Around 150 EUR for the 2 parts is not that expensive...

Will report back once (hopefully) fixed.

Thanks for your help ! Cheers.

[dingov70]

Sorry for not replying sooner ( been uber busy )

You buy quite cheaply the selection of required tools from Ebay ( about£20 in UK ) & then recover cost of tools by charging others for your time ( he he he )

or this https://www.amazon.co.uk/KKmoon-Alte...FKZ6E2HM1TS43P