Piston Slap or knocking?

[98Scooby]

I had noticed this when I first got the car, but then it got warm out and I didn't hear it again. Or if the car sits for a while I notice it as well.

So here it is. When I start the car when it's cold out it is rather loud, sounds like knocking, I assume piston slap. The longer it has sat the longer it goes for.

If the car has sat for a long period of time(a week or more) it starts super rough and then the noise last longer.

So my question is any idea what this might be? Is it due to oil draining out of the cylinders or what?

As for the cold, would an engine block heater help alleviate this problem?

I normally wouldn't worry too much, but it sounds horrendous. Especially when it has sat for a while.

[Harvey]

With your year and engine it sure sounds like piston slap. Nothing to be done about that.

[canubaru]

the link below may help. i think it says that rod noise will go away if you unplug the spark plug. but you better read it to be sure.

i would read up on piston slap. nothing is going to correct it short of replacing the pistons. but a different oil more lessen the noise a bit. for some reason i seem to remember a havoline 5w40 being a good choice. but you need to do some reading. i think i read about piston slap and oil on the ''ultimatesubaru.org'' site. try searching ''piston slap oil* '' keep the asterisk but lose the quotes.

Engine Noise Diagnosis 101

[98Scooby]

Thanks for the info. I think it might just be the oil draining, because the more I drive it the better it is. In fact the past two days it hasn't done it at all

[gezundheit]

i've had my 98 legacy wagon now for 5 years.it has 174k and the piston slap is part of it's behavior.she sounds like a diesel when first started but after she warms up she quiets down.i've tried every brand and type of oil to no avail.so,i got used to her infirmity.besides,the fix makes no sense,money wise.

[98Scooby]

Thanks for the info guys. I normally don't feel like its a problem other than when it sits for a week or two. I don't forsee it sitting that long again however so it shouldn't be a big deal.

[teamfalcon]

Is this the sound?

2003 Subaru Outback: Knocking sound - YouTube

[cardoc]

Originally Posted by teamfalcon

Is this the sound?

2003 Subaru Outback: Knocking sound - YouTube

I kept going back to this video with different speakers. My phone makes it sound one way, the laptop speakers sound another and external speaker surround makes it different again. But, the high pitch is lifters, lower tone sounds like a rod bearing. Got Oil?

[SE95]

The low tone sounds like the same noise every 2.5 I've ever heard makes when it is cold. The high tone sounds baaaad.

[98Scooby]

It definitely doesn't sound that bad, haven't noticed it too much lately. Still worrisome, found some metal shavings in the oil on the last oil change...