New M42 whine - would love some opinions on what it could be

[jsnppp]

Curious what you all think of this whine from my daughter's M42. This is a new sound that appears when it warms up a bit. Changes with RPM, not motion based. Doesn't change with moving the steering wheel. It will go away over time.

I haven't done a heck of a lot of analysis yet. Car starts, runs fine. I checked belts and none are extrememly loose but I'll take a look. When we refreshed the engine <10k miles ago we did water pump. Can't recall if alternator was replaced (I don't think so)..

All thoughts welcome!

[roguetoaster]

Take the belts off, which you can do one at a time if you prefer, and see if it's still there.

It does sound most like a bearing / rotating noise to me. But it could also be an intake leak, so you need to narrow it down first.

[jsnppp]

Cool, thank you - belts first for sure just to rule out stupid easy fixes. Would be great!

I was reading maybe chain tensioner but for whatever reason this doesn't feel like that, especially since it goes away.

It feels bearing-y to me too. My next hope is alternator, but I need to see if I replaced it already. I don't think so.

Appreciate the second set of eyes/ears!

[TobyB]

My 2c on early M42 noises-
make sure it's NOT the timing chain idler.
If it gets bad, it makes a mess of the front case.
I didn't buy one once because it had a 'small oil leak'
out of the case itself.
The person who did ended up rebuilding the engine...

It's easy to cut apart the oil filter to make sure there isn't
anything shiny in there, and it costs $6...

t

[jsnppp]

Thanks Toby - I'm pretty sure that I installed new idler when I did the profile gasket but new doesn't mean much perhaps. It's still possible its chain tensioner too... I'll look at my receipts.

I have yet to actually hear the sound outside of the video. She recorded it for me. It doesn't happen all the time (not sure if thats a clue or not) and it does go away. And it doesn't happen on first start. Engine has to warm up a bit first.

Thats what I understand anyway. She knows what I am going to ask and is getting good at filling in the details.

Jason

[jsnppp]

I've ordered a new AC belt idler and will swap alternator + check belt tension this weekend. Fingers crossed!

Daughter reports driving it today and the sound didn't appear....

[roguetoaster]

Don't overlook the alternator mounting bushings as a source for noise, and a great way to damage an alternator bearing.

[jsnppp]

Definitely will look carefully at it. Possibly tomorrow afternoon.

[jsnppp]

Status update. I tightened the alternator belt and replaced the idler pulley with another used one. Noise has not came back but it's only been a few days. It wasn't happening all the time.

Unfortunately I had ordered the idler pulley for an M44. Non v-belt. Not worth returning. If someone wants it just let me know - price of shipping.

I get the right idler pulley and a new, slightly shorter alternator belt on Thurs.

Noticed a slight weep of oil around a couple of the middle oil pan 10mm bolts while I was down there.

More soon!

[jsnppp]

So far the noise has not come back - this is great news. I haven't installed the new pulley or belt...

Here is the new vs. original pulley side by side.



Original has a worn groove in the pulley (shiny area). It's actually deep enough to have formed a ridge. Bearing feels fine but never know under load.


New lacks the groove...


Fingers crossed thats all it is!