High pitched squeal

[hopgop1]

Took my 182 for a quick drive this afternoon, when I got back and left the car running and got out to shut the gate I noticed a high pitched squealing noise from the engine bay. It seems to change with revs and gets a bit quieter at higher revs, but hard to tell with the noise of the engine. I'm fairly certain it's something on the aux belt line. Is there any easy way of narrowing it down? It doesn't go away if I turn the air con off.
Car had a full genuine aux belt kit fitted at AW Motorworks with it's cam belt in June 2020 and the car has only done roughly 16k miles since so I'm leaning toward it not being the tensioner and the belt doesn't look damaged from what I can see, I do know they need changing every 3 years though so I'm not far off that.

Is there anything easy I can do to narrow it down? Or has anyone had a similar noise before and fixed it? Car is on 141k miles now so I'd be leaning toward something that isn't changed at a belt service if there's anything obvious, an idler pulley or something?

Will attach a video of the noise below.

Any advice appreciated, cheers.

 

[hopgop1]

 

[JamesBryan]

Sounds like the alternator whining it's tits off 🤔

 

[hopgop1]

Sounds like the alternator whining it's tits off 🤔

That's a positive, well better than the water pump or something anyway. It did have a new alternator at some point I'm sure it's in the history, but I think it's a bosch unit. Car will end up at my mechanics anyway, but any recommendations on good replacement alternators? I'll do some research in prep.

 

[JamesBryan]

That's a positive, well better than the water pump or something anyway. It did have a new alternator at some point I'm sure it's in the history, but I think it's a bosch unit. Car will end up at my mechanics anyway, but any recommendations on good replacement alternators? I'll do some research in prep.

Only my initial thoughts, as it got louder as soon as you got close to the alternator.

If it does turn out to be that then a Valeo one is what you want.

 

[hopgop1]

Only my initial thoughts, as it got louder as soon as you got close to the alternator.

If it does turn out to be that then a Valeo one is what you want.

Cheers, will get it booked in next week, hopefully that's it.

 

[hopgop1]

To add to the mystery, only happens when the car is warm, e.g. 10-20 min drive. Car has gone to my mechanic today to be diagnosed, hopefully this week. Any further guesses?

 

[hopgop1]

Mechanic has sorted it apparently, will collect after work. The cause was a strange one, apparently the bolts for the plastic engine cover are slightly too long, opening up the manifold slightly and causing an air leak. I’ve not had that cover off for ages so God knows why it decided to happen now and only when hot. I bought new bolts on eBay I think when I changed the engine cover a while ago, so beware! Glad it was a cheap fix though and will be happy to have the car back.

 

[JamesBryan]

Mechanic has sorted it apparently, will collect after work. The cause was a strange one, apparently the bolts for the plastic engine cover are slightly too long, opening up the manifold slightly and causing an air leak. I’ve not had that cover off for ages so God knows why it decided to happen now and only when hot. I bought new bolts on eBay I think when I changed the engine cover a while ago, so beware! Glad it was a cheap fix though and will be happy to have the car back.

That's mad 😂

 

[hopgop1]

That's mad 😂

I almost don’t believe it myself! Will see when I pick it up, but it’s my mechanic who I trust very much and looks after all our family’s cars and has for years, so I doubt he’s wrong.
I’m sure I’ve got the old bolts about so I’ll compare them.

 

[SharpyClio]

Haha. Very honest as well. Good to know it was easy. Could the bolts have stretched slightly making them a shade too long?

 

[hopgop1]

Haha. Very honest as well. Good to know it was easy. Could the bolts have stretched slightly making them a shade too long?

That’s my theory, my fault for using shiny eBay replacements instead of the crusty originals haha. Car is no longer making a horrid noise confirmed after driving it back home this evening.

 

[SharpyClio]

That’s my theory, my fault for using shiny eBay replacements instead of the crusty originals haha. Car is no longer making a horrid noise confirmed after driving it back home this evening.

Been there done that had my brake caliper fall off (my push bike) because of the same thing shiny shiny = snappy snappy 🤣