Help identifying the issue

Hello,

Sorry for the very long post.

I have a 2004 WRX that has a knocking sound from cold startup.

Unfortunatelly my car is at the dealership for the next month, but before addressing them an inspection i would like to know what you guys think.

However this video is making the exact same sound and the exact same timing of mine, no difference at all: https://www.youtube.com/watch?v=Cpvs7uMtDvE&ab_channel=hooziewhatsit

I don't think it's the rods because:
- Oil pressure are perfect in any condition (highway, cruising, traffic, cold start). It goes a little low when very very hot (90-95C oil)
- Normal oil fluctuation, 1/3 psi max
- No burnt oil, i checked it after 6 months and it's still clear (i use the recommended 5w-30 Mobil 1 Oil)
- Dealership does not find anything in the pan (no flakes) changed 1 year ago
- it's almost 1 year and the sound didn't change a single bit or getting worse (not my daily tho).
- Car is never beaten or raced, always change gears before 2k rpm except made when uphill
- When cranked once, the sounds disappear for the next 1 - 2 hours after the car is shut
- I though it might be a low tensioner, full OEM transimission belt kit was installed last year (main and service belt changed, all the tensioners and pulley changed too).
- I know my AC pulley was done, but before changing the belt it didn't making any sound. Now it's screeching when AC is on.
- i know the guy at the dealership (50 years of experience) where the work has been done didn't use the tool to check the tension of the belt but it went by feeling
- if started without fuel to build oil pressure, the next start does not make any sound.
- when hot or cold, no sounds are recorded almost never
- No hesitations, no heavy smoke.
- it happens also when on heavy load (3-4k RPM) leaving the gas (hot or cold) to hear (me with the head literally in the engine bay) a single very very slight knock, no oil pressure changes tho, but i may suppose that comes from my exhaust heat cover (when closing the passenger door it rattles a bit so it might be loose).

I found the same sound and timing in different cars from diesels to petrol:
- This is on an honda: https://www.youtube.com/watch?v=x6SnC-FvmDc&ab_channel=DrtofuOno (same timing and sound)
- This is on a 2016 nissan xtrail: https://www.youtube.com/shorts/If45HuXU-8g
- This is 2007 (RX 350): https://www.youtube.com/shorts/tDVIR9bmtL4

So what you guys think? It's the rods or not?

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Originally posted on r/AskMechanics — View discussion