Scary metallic noise from engine
 

Howdy all, recently I went to start up my FR-S for a weekend drive and was greeted with the following terrible metal grinding sound (see video link below). :( Best heard after 0:04 when I'm zoomed up on the throttle body and alternator areas.



https://youtu.be/hjDFo-Zo9M8



This sound appeared out of nowhere, no indications of problems on my last drive, which was only a day or two before this start up. Recently I did replace the serpentine belt, to get to which I had to remove parts of the intake.


The fact that its an inconsistent sound seems to me there must some kind of debris in either the intake or engine proper (maybe valve spring broke?). I'm also not terribly familiar with what engine pinging (i.e. combustion instability) sounds like, perhaps that's this? Cars got ~75,000 miles and is a 2013 FR-S.



I was wondering if anyone else has encountered a similar sound or had ideas as to what it could be. I'm planning to get a borescope into the engine at some point over the holidays as have a look around. Want root out as much as I can before taking it to a shop.



Cheers!

i hear metal debris hitting a wall?

It has a bit of a "ring" tone to it. Not sure it is internal at all. It also is oddly irregular which would not be likely with something internal since there is not a pile of space for parts to randomly bounce around. The engine seems to be running perfectly fine other than the npoise but hard to tell with a short video.

Take the belt off, start it up again. See if the noise changes or goes away.

This is why it is very important to read the WHOLE post! I totally missed the mention of the belt. The inconsistent ringing is completely compatible with a bouncing tensioner.

My reading comprehension is questionable, but it seems the noise may have started after he replaced the belt.

Exactly!

Between replacing the belt and hearing the noise I had taken the car for a couple drives without hearing anything discernable. If I have time tomorrow I will try taking the belt off and seeing the result. Might not be able to get to it till after the holidays.