Plasticky sounding rattle / ticking from engine

[Pete McCue]

Good afternoon all, my car has always, (in my ownership), had this strange plasticky sounding rattle or tapping/ticking noise from the driver's side of the engine bay. It's not constant and only noticeable at idle. It's definitely not valve clearances as I've had a good listen to those and they all sound sweet as a nut. I wondered if it might be the alternator? Should have run the engine for a bit when I had the aux drive belt off. Any ideas? Cheers.
I did make a short video but don't know how to put it up.

[Carolyn]

It could be a tired chain tensioner.  They are tensioned by oil pressure and, if they are a bit worn, they can fail to tension properly at idle.

If it is the tensioner, it might only happen once the oil is warm and idle oil pressure drops.

Otherwise, as you say, pop the belt off and give it a listen.

[Pete McCue]

It could be a tired chain tensioner.  They are tensioned by oil pressure and, if they are a bit worn, they can fail to tension properly at idle.

If it is the tensioner, it might only happen once the oil is warm and idle oil pressure drops.

Otherwise, as you say, pop the belt off and give it a listen.

Thanks for that. I did wonder about that but it's such a plasticy sort of sound I wasn't sure. The car's only done 43k but I suppose for £40 I could do it anyway couldn't I.

[Pete McCue]

Ok, so fitted a new timing chain tensioner, nice 10 minute job but made no difference. Will hopefully post a video here to see if anyone recognises the noise. I'm not concerned by it, it's just annoying. Not sure why the engine sounds like a tractor! 

[Call the midlife!]

Have you checked your flexis for holes? Sometimes the gas escaping from the weave can make a strange noise like that.
Obviously this is assuming the tensioner sprang out of the clip properly before starting up.

[Pete McCue]

Have you checked your flexis for holes? Sometimes the gas escaping from the weave can make a strange noise like that.
Obviously this is assuming the tensioner sprang out of the clip properly before starting up.

Cheers.
You mean make the engine sound like a tractor or the clicky/tappy noise? The engine sounds fine "in real life".
The tensioner definitely clicked into place.

[Call the midlife!]

Either/or/both... it kind of flaps as the exhaust blows through it.

[Pete McCue]

Had another look at this today as it's a lovely day out there. Exhaust flexys are fine. I'm pretty sure it's coming from the aux belt tensioner assembly so I've ordered a new one to see.

[Pete McCue]

No more clickety-clack! Happy days.
It also means I've got a perfectly good timing chain tensioner if anyone needs one for just the postage?

[Carolyn]

No more clickety-clack! Happy days.
It also means I've got a perfectly good timing chain tensioner if anyone needs one for just the postage?

Hold on to it.  They don't last forever.