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2004 Outback LL Bean H6 3.0 Silver 175K
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Discussion Starter #1
I took another look at my engine pistons as it has been sitting for a while waiting to be swapped in, and this is what they looked like. I can't tell if this is regular carbon buildup from the last time the engine was in a car or if this is the dreaded pitting which will have me looking for a new ez30d


 

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2017 OutBack Premier, 2019 Forester Ltd, 2016 370z Rdstr
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722 Posts
samxerxesn,

Its easy enough to tell if you rotate each piston to top dead center and the scrape the piston top clean with chisel-like tool to remove the carbon and see the piston face. Be careful not to score the piston face or the cylinder bore lip. Then judge for yourself.
 

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2005 OBXT Limited, VF37, STI intake, 5MT
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1,571 Posts
The edges of the piston look like it's been rounded and worn away. Looks like a combination of detonation and potentially debris in the cylinder(s).

I would do a "hillbilly" leak-down and see if there's air leaking in those cylinders.

"hillbilly" leak-down test is a compressed air line to the spark plug hole while the piston is at TDC and listening for excessive air movement. No gauges, but it helps tell you if you've got a burned valve or cracked ringland.
 

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Looks like a lot of detonation at the quench area. Typically happens when you get a lot of carbon build-up on the piston.

You can compression test it, but at a minimum you need to run a can of seafoam through the engine, or even better yet ... setup a very crude water mister and let it run for a bit while you drive down the highway.

Personally, I'd rebuild the motor or get a used replacement.
 
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