So here is mine. 01 Legacy. 2.5. 120K.....When I first start the car it's a pretty loud knocking sound. Enough that I have to duck down as I drive by the bus stop because all the kids laugh and point at me. It's mainly at idle and low acceleration. At speed, I can't hear it anymore. Once it's warmed up, it almost completely goes away, but you can still hear it a lil bit. problem is my longest drive is at most 4 miles so it never really get's a chance to warm up...anyway, so what's everyones thoughts? rod knock? main bearing? timing belt tensioner? All 3? Woodpecker in my exhaust manifold perhaps? It's a deepish knock knock that speeds up with engine rpm to a point and then it sort of, well, goes away.....grrrrrrrr the 2.5, 2.2 for the world!

Do a search on piston slap and see if it sounds similar.

So here is mine. 01 Legacy. 2.5. 120K.....When I first start the car it's a pretty loud knocking sound. Enough that I have to duck down as I drive by the bus stop because all the kids laugh and point at me. It's mainly at idle and low acceleration. At speed, I can't hear it anymore. Once it's warmed up, it almost completely goes away, but you can still hear it a lil bit. problem is my longest drive is at most 4 miles so it never really get's a chance to warm up...anyway, so what's everyones thoughts? rod knock? main bearing? timing belt tensioner? All 3? Woodpecker in my exhaust manifold perhaps? It's a deepish knock knock that speeds up with engine rpm to a point and then it sort of, well, goes away.....grrrrrrrr the 2.5, 2.2 for the world!

 

 

Sounds exactly like my '99 Forester. The only cure(piston slap) was a complete rebuild, with slightly larger pistons from Subaru.

I've learned to live with my 99 Forester's slapping when cold. Its oil tests were good and it is quiet when warm. On a very cold day with old oil in it the best description I have heard was a woodpecker.

I had a '98 OB (Phase I - 2.5) that had the piston slap - it had 114K miles. I took it to 3 shops (no dealers) and none could really diagnose it - other than suggest a rebuild. That was about the time I found this site and learned about the issue.

 

If it does go away, then it's likely p-slap. I read where Subaru actually considered this normal.

 

Here's a link:

http://www.butkus.org/subaru/piston_slap/subaru_piston_slap.htm

 

The movie link doesn't work, but looks like it was covered by warranty, which tells me maybe it's NOT normal?

 

Here's a Subaru letter saying it's normal:

http://cs.senecac.on.ca/~selmys/subaru-letter.txt

here's the original link:

http://cs.senecac.on.ca/~selmys/subaru.html

 

 

 

Would different weight oil help? Probably not since it's above the oil?

 

Good luck

Well if it is just piston slap, I can live with that since it isn't a big concern. I'm sure it will run along time as long as I can live with the noise (I wonder if synthetic will quiet it up some since it tends to "stick" more?) It's just the main bearings or rod noise that would concern me since who knows how long it would last like that......diagnosing "noises" isn't always an easy task lol

read this on diagnosing piston slap.

 

http://remanufactured-engines.com/page4.htm

My wife's Forester had a new tensioner fail after two weeks and I have to admit that I thought it was much worse than that. It really sounded like the mechanical world was ending in that motor. The same shop that put it in replaced it free and it's been "quiet" ever since.

A bad tensioner can be very loud...