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Old 06-29-2001, 10:13 AM   #1
Kachukaa
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Member#: 2527
Join Date: Sep 2000
Location: Richmond, VA
Vehicle:
1997 Legacy 2.5GT
Quicksilver Metallic

Default Piston Slap Question

Posted this is the legacy forum, but I guess I'll should post here too. I have a 97 2.5GT and recently I've been hearing a clicking or tapping noise at all RPM's coming from the engine. I'm worried it's piston slap but I don't know how to tell for sure. Also how can I get the dealer to fix this for me? I asked about the noise and they said it was nothing, but I still suspect that is what it is. I have 100k mile extended warranty so as this is an engine internal they should have to fix it.
Thanks in advance,

Pete
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Old 06-29-2001, 10:17 AM   #2
Grap
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Pete -

I would suspect lifter or valvetrain noise over piston slap. If you are getting interference between the pistons and the valves, you have BIG problems. Your oil pressure might be low or you might just be low on oil. Check those first. As I found out from people on this board, 2.5's are noisy motors even with less than 100k miles on them.

Good luck!

-Brian
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Old 06-29-2001, 10:42 AM   #3
Ken S
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05 Leg GT Ltd. W
Silver

Question Piston slap

Can you describe the noise a little more? Does it go away once your vehicle warms up?

The solid lifter noise is often a lighter "click, clack" noise and should pretty much go away once the engine warms up. Piston slap has a heavier sound, kind of like a muffled metal-on-metal noise. Piston slap is most noticeable when the engine is cold, but it can persist even after the engine warmed up. It's also more noticeable when you lift off the gas and let the rpms drop.

Ken
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Old 06-29-2001, 11:05 AM   #4
Clegg
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Default

Yep, coming from driving a Dodge Stratus, and other smaller 2.4 L Inline 4 engines, the Boxer 2.5L is MUCH noisier ( when you are driving and go past a building you can hear the engine noise reflected back at the car off the wall and you can tell its a loud beyatch
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Old 06-29-2001, 11:11 AM   #5
iBlueVirus
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Really? I always thought my car is so quite, even my friends say so. I guess it's because my baby is still 'young'.
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Old 06-29-2001, 11:20 AM   #6
Grap
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Talking

You must have one of those one-off prototype deals. Mine has made a ton of noise since it had 2K on the clock.

On the original topic, I have been thinking that maybe it could be rod knock? If you lost oil pressure for any real length of time or were low on oil, you could have wiped one of your crank bearings.

When you refer to piston slap are you talking about the pistons slapping the valves or are you saying that it might be the pistons slapping around in the cylinders?

-Brian
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Old 06-29-2001, 11:21 AM   #7
Kachukaa
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Ken,

The noise is a constant clack that does not go away when the engine warms up. This is what led me to believe it was piston slap. I listen for it and the sound is produced from idle all the way to red-line. I guess I'm going to have to go b#tch at the dealer again to look at it again. What is the fix if I have piston slap? What will the dealer do to prevent it happening again?
Thanks

Pete
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Old 06-29-2001, 01:08 PM   #8
Ken S
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Unhappy Piston slap

Sounds like it could be piston slap. The best thing to do is take it to a dealer and have them look at it. If they say it's normal, call SOA, get a case # assigned and keep pushing until they get someone to look at it.

The 97-98 DOHC engines use skirtless pistons. The skirtless design reduces friction but gives up stability resulting in "slap" -- the sound of the piston hitting off the cylinder wall.

Subaru does have a remedy out for piston slap with pistons that have been machined to tighter tolerances. You need to be very vocal about it before they offer that fix to you, however. They'll usually try and tell you that the noise is not going to hurt the engine. I had it on my 98 Forester and it took a visit from the local district technical manager for SOA to approve it.

Try a search on piston slap. There's quite a bit of info on i-club regarding this.

Hope that helps.

Ken
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