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Old 12-17-2012, 10:28 AM   #1
jim662
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Member#: 338593
Join Date: Nov 2012
Location: Richardson, Texas
Vehicle:
1999 Legacy Outback
White

Default Is it rod knock, piston slap or something different?

The video link below is on my 1999 Outback 2.5L DOHC motor that I just got done replacing the main and rod bearings on. The pistons had some slight wearing on the skirts. Motor had 200,000 miles. I replaced the piston rings as well.

the video:

You can hear the noise in the video. It seems to vary with temperature. When dead cold, it sounds like dieseling and it is louder. When warm, you don't hear the noise at RPMs above 1,500. You don't hear it while under load when warm. While it will change with how warm the engine is, the noise is always there. It never completely goes away.

I've changed out the timing belt tensioner and the noise is uneffected. The noise is definitely on the driver's side. I've listened with a mechanic's stethescope and my best guess is that it is either the front driver piston or the valves front valves. It is possible that the waterpump could be the issue as it is right down there in that area and it was stamped as remanufactured.

So, I'm looking for thoughts and suggestions. I really don't want to have to pull the motor again, but you got to do what you got to do. I've not moved spark plug wires around yet and I've not cleaned the MAF. My experience is that a dirty MAF will exhibit knocking while under load, not at idle. Besides, this sounds more like a mechanical issue.
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Old 12-17-2012, 10:53 AM   #2
Charlie-III
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Chapter/Region: Tri-State
Location: 07456, North NJ
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1998 Legacy 2.5GT
Silver Sleeper Wagon

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Was that with a warm engine or cold engine?
Did you get the pistons back in the same cylinders?
Was there a "ridge" at the top of the cylinders? (If there was, did you remove it?)
What HG's did you use?

It dosen't really sound like a rod/main bearing to me. They usually get worse under load though.
Also, usually a rod/bearing going bad will trip a "knock CEL", P0463.
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Old 12-17-2012, 11:07 AM   #3
jim662
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1999 Legacy Outback
White

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The video was with the engine not stone cold, but not warmed up all the way. Maybe a couple of minutes at ilde only.

Pistons went back in the same cylinders, facing the correct direction. There was no ridge at the top of the cylinders. I used the Fel-Pro MLS head gaskets. Rod and main bearings were replaced with new. It is not throwing any codes.
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Old 12-17-2012, 06:52 PM   #4
jim662
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1999 Legacy Outback
White

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I uploaded a video with it running without the valve cover. I sure don't hear the noise. Maybe some under acceleration, but that may be piston slap. It blows out about 1 quart of oil every 15 seconds.


edit: after driving for about 15 miles, the noise is back, but not quite as bad. The only thing I did when I had the valve cover off was to rotate the buckets covering the valve springs. They moved freely. I'm wondering if one has a worn spot.

Last edited by jim662; 12-17-2012 at 09:58 PM.
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Old 12-17-2012, 08:17 PM   #5
Counterfit
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That's a lot of oil. Did you re-hone the cylinder walls? I think after 200k, you would need at least that, if not a rebore to get the cylinder back to round.
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Old 04-28-2013, 09:39 PM   #6
djgoldeneye
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did you find a solution to the knocking sound. i saw on another thread that it could be the "up pipe"?? did you try that?
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Old 04-29-2013, 03:12 AM   #7
Counterfit
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There's no up pipe on OP's car.
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Old 12-07-2013, 01:30 AM   #8
DeviAnt985
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Solution to the knocking sound? I did my valve cover gasket and my spark plug tube seals today and did a valve adjustment. I put them at .008 intake and .010 exhaust at TDC. When I restarted it, It sounds the same as the first video and will stall if I put it in gear.

07 2.5i automatic trans 97k miles
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