Irregular cracking noise from engine
 

Does anyone have an idea what those irregular "cracks" coming from?
https://youtu.be/PXql0Lxasjs

Do you know the repair history on the car? What year is your car? Trans type? The audio is difficult to sort out. At the very least, I would suggest you not drive/run it until you sort this out. Pull the oil filter and cut it open and look for shiny bits. If it is your IMS bearing failing, you can't risk any more revs of the engine.

My lord that sounds like a washing machine full of marbles. I would not start it again until I found out what was wrong. On a side note the under side of the car looks really clean.

I would suggest taking off the engine cover behind the seats and removing the belt. Start the car, and if you hear the noise again shut it off immediately and flat bed it to a shop. Other than that, don't run the car. If the noise is gone with the belt off, spin the accessories by hand to find the bad actor. If the noise is internal to the engine and present with the belt off it is possible for it to play out into engine failure if it is not addressed. Best of luck!

I don't have history but engine seemed to be virgin when I bought it. I changed IMS bearing, water pump and serpentine pulleys. Original oil and filter were without particles. Original IMS bearing was in perfect shape. I rebuilt transmission (with some issues). I drive car in this condition for a while. Transmission has some noises but I would expect them to be periodical (due to bent teeth maybe, I hope it would go away after break-in). Also, when clutch is off there is no change. Crackling sounds like some loose metal pieces, very close to what exhaust makes just after engine is turned off. This is Boxster S '02 with 68K miles.

Since you did the work, do you remember if your clutch plate had springs in the frame? I had a clutch spring break and rattle in-between the plate and flywheel. (old Chevy truck) It was drive able, but it made a hell of a racket.

You note that you rebuilt the trans and had some issues. And that it made some noise and bent teeth. None of those thoughts are encouraging.

I have dual mass flywheel (it put brand new) and my clutch disk is solid piece. As for bent teeth, well lesson learned. Still, depressing the clutch (transmission is totally off) changes nothing.

To the OP, did you ever figure out what was causing this noise?

He hasn't been on the board for 5 years...