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Knock source

  • Rod

    Votes: 1 33.3%
  • Timing belt tensioner

    Votes: 0 0.0%
  • Wastegate head shielding

    Votes: 0 0.0%
  • Something else

    Votes: 2 66.7%
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Discussion Starter · #1 ·
Hello folks,

Helping an old high school friend who's experiencing some major health issues put his 2005 STI up for sale. I obviously want to help him maximize the amount he gets for the car so I've been helping him prepare it after it has been sitting for about a year.

My friend told me he parked the car when it started making a sound but wasn't sure what it was and didn't have time to look at it because his health was just starting to fail at that time. I thought it might be a sticky lifter or something similar because it wasn't being driven much before it was parked.

Checked the oil level (full), battery (dead), and gas (not varnished), and decided to try to start it. I had to jump it off my diesel truck because of the battery, but I was pleased to see it start right up and hold a steady fast idle. No undue sounds to be concerned about at first glance. However when I started to gently rev the motor to warm it this is what I heard, right around 2,500/3,000 RPM. When I move around to the engine, you'll also notice that there was some slight smoke coming from the wastegate area but I think that was just organic debris ie. leaves burning but I could be wrong:



To my ears, this sounds like rod knock, but my second thought was that it could also be a failed timing belt tensioner. I understand that the heat shielding around the wastegate on these cars can also produce a similar sound, so I'd figured I'd let some of the experienced owners in this forum take a shot at helping me diagnose here. I know it's not ideal trying to diagnose knock with my diesel clattering away in the background, but I'll try to get better video this weekend once I've got a new battery in it. In the meantime, I'd appreciate some second and third opinions here. Thanks in advance.
 

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Sounds like rod knock to me.

Get yourself a real extra long screwdriver. Put it to the block behind the alternator on the crankcase and put your ear to the other end. Have someone rev the engine up to duplicate the noise. If you can clearly hear that noise in your ear through the screwdriver then its an internal engine issue. Try this trick on multiple spots of the block and crankcase.
 

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Agreed, sounds like rod knock/spun bearing.

If you feel like simply draining the oil, it might be a bit glittery/metallicy looking.
 
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Discussion Starter · #6 ·
Forgot to mention that I spoke with the owner last night and he shared that he had just changed the oil that day, drove the car about a mile to a convenience store and the engine started making that noise, slightly at first then louder, on that trip.

I saw some other threads where that situation occurred, ie. spun bearings happening right after oil changes so I would say that is more evidence that this is a big end bearing issue.
 

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Y'all need to learn the ways of the Jedi noise evaluation master who uses a 3/8" drive 24" extension as a diagnostic tool. You can set the end on various spots of the engine to better identify the source of the noise. Or any long metal rod set against the tab of your ear and the block/head/tensioner cover.😎
 
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