Subaru motor knocking on heaven's door

2009 Forester 2.5L non-turbo

It rattles on startup and I can hear a faint knocking sound after it warms up.  I've detected very light shavings in the oil so the motor is not long for this world but i think i caught it early.

Anyone had success (or short term success) with thicker oils or magic mixes?  I was thinking a Wal-mart 20-50.  It has a 5-30 in it now. 

I have nothing to lose at this point but i don't want to cook the heads either.

Engines are never around when you need one.  This is a EJ253 I believe.  It still has the single came w/timing belt.

I think Subarus tend to suffer from piston slap when cold.  If it gets better after it warms up, I'd think it's less likely to be rod knock.  Is the metal ferrous?

EJ253.

If you can cut the oil filter open and the media is not full of big sparklies, with extra chunks in the canister, it's probably just piston slap.  Especially if it is near 200k miles.  Subaru engines for whatever reason are extremely sensitive to piston skirt clearance.  The tolerance spec, IIRC, actually prefers a piston larger than the bore, for an interference fit when cold.

Relocate the knock sensor to the bellhousing area (there should be a bare 8x1.25 threaded hole perfect for this) so the computer does not interpret slap as knock and thereby adaptively pull ALL the timing below 2200rpm, and keep on truckin'..

On worn EJ22 engines, they would adaptively pull so much timing that from a stop a worn out Mercedes 300SD would out-drag it, and then at 2200 the ECU would go into a different timing cell and WHAM the engine would wake up.

4 qts 20w50 and a bottle of Lucas did not reverse the sparkly-removal process in the EJ253 of our 2010 Forester. 

In reply to AngryCorvair (Forum Supporter) :

What did you end up doing with yours?  Replace the motor with a used one?  That's what I'm leaning towards but I'm going to drop the pan soon and investigate further.

In reply to fornetti14 :

Couldn't find a warranteed replacement EJ253 under $2k within a couple hours of here, and didn't really feel like berkeleying with an engine swap in my driveway in December, so sold the car to a local Sube dealer tech for $1700.

Define "Rattles on startup".  If it rattles quite sharply for a second or so, and quiets suddenly, when the oil pressure hits, you have a bad rod bearing, and all the Marvel Mystery Oil in the world won't fix it.  If it rattles and gradually lessens over a minute or two, it's shrunken pistons, and will probably run for quite a while.  

My baja had so much piston slap in the winter startups it sounded like a diesel.  For 2 winters.  Drive gently till it warms  up and turn up the radio.  The newer computers don't retard timing as much, so just drive it.  Keep looking for a replacement engine or in the summer when it knocks less sell it.

Streetwiseguy said:

Define "Rattles on startup".  If it rattles quite sharply for a second or so, and quiets suddenly, when the oil pressure hits, you have a bad rod bearing, and all the Marvel Mystery Oil in the world won't fix it.  If it rattles and gradually lessens over a minute or two, it's shrunken pistons, and will probably run for quite a while.  

Collapsed hydraulic lifters also fit that description, but it's more of a high pitched sewing machine noise than a deep rattle. They will not continue to make noise once pumped up.

In reply to Keith Tanner :

EJ253 doesn't use hydraulic lifters like the earlier motors so maybe it needs a valve adjustment but I'd be surprised.

My 07 Legacy (same motor) with 330,000 km (205,000 miles) has lots of piston slap on cold start up but quiets down once warm. I'd recommend taking a long extension and using it like stethoscope, put one end on various parts of the engine while it is running and at operating temp and the other against your ear. You'll be able to dial in where various noises are coming from, mainly you want to see if that knock/tick is coming from the head area (valve adjustment or fuel injectors) or from the centre of the crankcase where it would be rod knock. I did an oil change the other week and did this just for piece of mind as the piston slap isn't super reassuring once winter hits. 

I run Shell Rotella T6 0W-40 in the winter and 5w-40 in the summer in my car after spinning a rod bearing (presumably, didn't spilt the case) on the original motor. I was lucky to pull my current motor out of a pick-n-pull so the cost was low and this enigne has been perfect for me other than the slap.

Given that the noise reported continues after oil pressure arrives, it's unlikely to be lifters anyhow. That was more of a generalization.

With my Subaru engine experience, I'm assuming total carnage inside. But I'm hoping that's not the case.