Rattle at 2000rpm - Stumped!

[acealfa]

Hi all,

I have an Alfa Mito 1.4 16v (non turbo) I could do with some fresh ears & thoughts as to what this noise might be. It does it around 2000-3000rpm and so far I've inspected or changed the following;

Auxiliary components (air con pump, alternator pulleys)
Cambelt tensioner
Engine mount
Exhaust bracket
Conrod bearing shells

It sounds like it's from the rear of the engine but hard to tell really.

https://www.youtube.com/shorts/5sPwLU93HY8

Thanks

[stevieturbo]

instead of replacing parts.

Does it make the noise with the auxiliary belt removed ? That would verify if you needed to change any of those parts.

It sounds loud in the video...so can anything be felt on any part of the engine ? With a stethoscope, does it seem louder on any part of the engine ?

[DWDarkWheels]

Agreed with StevieTurbo, remove the belt to eliminate a load of ancilliary parts.

Anything external on the engine loose that might vibrate at its resonant frequency?
I had a broken weld on the exhaust heat-shield. The edges rubbing sounded like a dry bearing in the alternator or similar.

[acealfa]

stevieturbo said:

instead of replacing parts.

Does it make the noise with the auxiliary belt removed ? That would verify if you needed to change any of those parts.

It sounds loud in the video...so can anything be felt on any part of the engine ? With a stethoscope, does it seem louder on any part of the engine ?

Sorry I wasn't clear in my post, noise is still there with aux belt removed thus eliminating all ancillaries. Cambelt was due anyway so ruled that out.

I've ordered a stethoscope so if I can get any closer. I'm going to tilt the engine forward off the mounts tomorrow & check bolts for alternator & air con pump.

[stevieturbo]

acealfa said:

Sorry I wasn't clear in my post, noise is still there with aux belt removed thus eliminating all ancillaries. Cambelt was due anyway so ruled that out.

I've ordered a stethoscope so if I can get any closer. I'm going to tilt the engine forward off the mounts tomorrow & check bolts for alternator & air con pump.

if you removed the belt....how can the alternator or aircon pump make any noise ?

And you think the noise is from the opposite end of the engine ?

Does clutch etc feel normal ? Does it affect how it drives ?

[GreenV8S]

What's flying around the pulley in that video? It looks almost like swarf coming from somewhere near that top pulley.

[E-bmw]

GreenV8S said:

What's flying around the pulley in that video? It looks almost like swarf coming from somewhere near that top pulley.

^^^^Wot 'e said.

There is something shedding lumps/sparks there as can clearly be seen in the video.

It is likely that something has moved, possibly due to a collapsed engine/gearbox mount or similar.

You say you have checked/changed them, you need to look closer & I am sure it will be obvious.

[Rockets7]

Whoa. I’d be in that top pulley, that’s ripping something to shreds !

[tapkaJohnD]

Something steel is striking something else, at the critical engine speed, causing the sparks.

This points straight at the harmonic damper on the front of the crankshaft. The rubber ring that bonds the hub to the outer inertia ring has probably broken down.

I don't know Alfa engines, but this is probably a straightforward replacement, if there is access.
John

[stevieturbo]

GreenV8S said:

What's flying around the pulley in that video? It looks almost like swarf coming from somewhere near that top pulley.

I wasn't sure if that was some sort or reflection from the video or something. But something did look odd...but then it seemed to disappear too.

but if he claims the noise is still there with no accessories being driven....perhaps a red herring ?

Although I cannot understand if there is noise with no belt, why he would then want to start unbolting accessories that are belt driven....with no belt lol.

[acealfa]

It's just loose dirt from where I'd cleaned out the scuttle panel area, nothing sinister.

The noise is cambelt end at the back near the bulkhead. I just wanted to check the alternator is bolted properly but access is pretty tight. I'll also try & get a better video hopefully later today.

[stevieturbo]

acealfa said:

It's just loose dirt from where I'd cleaned out the scuttle panel area, nothing sinister.

The noise is cambelt end at the back near the bulkhead. I just wanted to check the alternator is bolted properly but access is pretty tight. I'll also try & get a better video hopefully later today.

Generally the "front" of the engine is regarded as the cam belt area, water pump etc. The rear is the flywheel end.

So you're saying the noise [i]is[i/] at the front of the engine....to the rear of the engine compartment. ie. not the flywheel or gearbox end.

Whoever changed the timing belt tensioner, did they not have a look inside ? Why just the tensioner and not the belt and any other pulleys ? Does it make a difference with those covers off or on ?

[acealfa]

Dropped the engine forward and removed the aircon pump to finally find the cause! Loose bolt on the alternator. Time for a beer 🍺

[stevieturbo]

And it was making noise with no belt attached ? weird.

But well found.