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2003 2.5RS
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Discussion Starter #1 (Edited)
Lately when I go to start up my car, there is a noise that is inside the engine bay that sounds like a fast pace tick, rattle or knock. I'm not sure which "noise term" is the correct one and I'm sure there are plenty of grammar nazis that will correct me or tell me which one it is but I just know that it sounds something along those lines.

But I digress, it seems to only be when the car is cold. Once it warms up it does go away but until it gets about half way on the water temp gauge it makes the noise. It's not super loud, but you can hear it. Also, if you drive before it is fully warmed up, it's only in the lower RPMs that you can hear it, past 2.5k it goes away. It has been consistantly below 30 degrees here in Idaho, most of the time around 5-15.

So what are my likely scenarios? Sticky lifter(s)? Would a higher viscosity oil help (like 10w-30 instead of 5)?

It's an 03 RS w/202k miles and bone stock as far as motor goes. Using castrol syntec and a bosch filter.
 

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2000 2.5RS/C BRP
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A few questions:

Does it sound like a rythmic knock, or a sort of clattering noise?

Is it a crisp sound, as though it's someone knocking on a piece of metal, or a dull sound, like rolling marbles in a tin can?

My first guess is just piston slap. My car does this as well once the temperature hits the teens. Obviously, you can ignore this, just don't hammer on it until warmed.
 

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Discussion Starter #3
A few questions:

Does it sound like a rythmic knock, or a sort of clattering noise?

Is it a crisp sound, as though it's someone knocking on a piece of metal, or a dull sound, like rolling marbles in a tin can?

My first guess is just piston slap. My car does this as well once the temperature hits the teens. Obviously, you can ignore this, just don't hammer on it until warmed.
I'd say it is more rhythmic, it's nothing like a clatter from a pulley or anything.

I would have to go with more dull than crisp however that can change with the temperature discrepancies.

However what does worry me a little, assuming you are correct, is that piston slap doesn't always equate to something that is nothing to worry about, right?
 

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Discussion Starter #4
By the way, sorry if I posted in the wrong thread. Probably should have gone in maintenance.
 

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BRP '01 2.5RS 4EAT coupe
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If it's like a ticking noise that speeds up along with accelerating then every older Subaru I have driven makes that same noise: my RS, my mom's 2001 Outback, and my dad's 96 Outback. I'm 99% certain it's the piston slap thing people talk about. I have even gone so far as to ask the Subaru dealer whether my car sounded normal to them because I thought it seemed loud, and they told me it was completely normal and that will be $50, please. If you go to YouTube and search for Subaru piston slap you can find some engine noise recordings that will probably sound familiar to you.
 

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I'd say it is more rhythmic, it's nothing like a clatter from a pulley or anything.

I would have to go with more dull than crisp however that can change with the temperature discrepancies.

However what does worry me a little, assuming you are correct, is that piston slap doesn't always equate to something that is nothing to worry about, right?
If it's like a ticking noise that speeds up along with accelerating then every older Subaru I have driven makes that same noise: my RS, my mom's 2001 Outback, and my dad's 96 Outback. I'm 99% certain it's the piston slap thing people talk about. I have even gone so far as to ask the Subaru dealer whether my car sounded normal to them because I thought it seemed loud, and they told me it was completely normal and that will be $50, please. If you go to YouTube and search for Subaru piston slap you can find some engine noise recordings that will probably sound familiar to you.
Ticking and piston slap are two VERY different sounds. Piston slap is like there's something inside the crankcase that's getting tossed around (sort of like a off-balance washing machine), whereas the ticking you're talking about is very clear and sharp because it's valvetrain noise. Something about the phase II SOHC heads lends itself to really bad valvetrain noise. I did my valves three times, and it would change but never leave, and then I had our mechanic do it, but even then it was only a change.

OP, you're right, it's not always good that you have piston slap. But as you only notice when the car is very cold, what you're hearing is the larger thermal expansion coefficient of the aluminum pistons vs the steel cylinder walls. Basically, in the very cold, the pistons shrink farther than the cylinder walls do. Once the pistons warm, they fit more tightly. So if you only hear it when it's very cold out, and once the car is warm it's gone, don't worry about it. If it's always there, then you have cause for concern. Our flat engines are more prone to piston slap than traditional I-4s.
 

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Discussion Starter #7
OP, you're right, it's not always good that you have piston slap. But as you only notice when the car is very cold, what you're hearing is the larger thermal expansion coefficient of the aluminum pistons vs the steel cylinder walls. Basically, in the very cold, the pistons shrink farther than the cylinder walls do. Once the pistons warm, they fit more tightly. So if you only hear it when it's very cold out, and once the car is warm it's gone, don't worry about it. If it's always there, then you have cause for concern. Our flat engines are more prone to piston slap than traditional I-4s.
Okay that's comforting. Is there anything I can do to minimize it? Or should I really just relax and not worry about it?
 

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So what are my likely scenarios? Sticky lifter(s)? Would a higher viscosity oil help (like 10w-30 instead of 5)?

It's an 03 RS w/202k miles and bone stock as far as motor goes. Using castrol syntec and a bosch filter.
I've been using this oil since I've own my Impreza as well but in near freezing conditions you may actually want to consider a thinner viscosity like 5W__ or even 0W__. I myself having been using Castrol Edge (new name for Syntec) 5W50 year-round for years and it covers me across the temperature spectrum...

I'm personally not a fan of Bosch anything but if it's been working for you then 'ain't broke, don't fix it'.
 

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Discussion Starter #9
I've been using this oil since I've own my Impreza as well but in near freezing conditions you may actually want to consider a thinner viscosity like 5W__ or even 0W__. I myself having been using Castrol Edge (new name for Syntec) 5W50 year-round for years and it covers me across the temperature spectrum...

I'm personally not a fan of Bosch anything but if it's been working for you then 'ain't broke, don't fix it'.
I'm already using a 5w-30, not sure I want to go any thinner with this many miles. I usually use a Wix filter but Bosch was on sale.

Would something as silly as an additive like Lucas help?
 

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I'm already using a 5w-30, not sure I want to go any thinner with this many miles. I usually use a Wix filter but Bosch was on sale.

Would something as silly as an additive like Lucas help?
5W should be fine for the cold temps, it's already one step below the 10W that's recommended. You might consider going thicker on the hot side, but that won't affect the cold performance. From what I hear, the Bosch & Subaru OEM filters are the only ones with the "correct" pressure relief.

As for fixing the piston slap, there's really nothing simple you can do. A full engine rebuild would cure it, but you know. Overkill and all that. :lol: Just drive it gently until it's warm, you should be fine.
 

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Discussion Starter #11
5W should be fine for the cold temps, it's already one step below the 10W that's recommended. You might consider going thicker on the hot side, but that won't affect the cold performance. From what I hear, the Bosch & Subaru OEM filters are the only ones with the "correct" pressure relief.

As for fixing the piston slap, there's really nothing simple you can do. A full engine rebuild would cure it, but you know. Overkill and all that. :lol: Just drive it gently until it's warm, you should be fine.
Okay awesome, thank you guys for the help. I'm still getting used to boxer motors and the whole pistons going sideways thing. Remember, some of you guys are the reason I bought an RS over a Lancer.
:banana:
 

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Okay awesome, thank you guys for the help. I'm still getting used to boxer motors and the whole pistons going sideways thing. Remember, some of you guys are the reason I bought an RS over a Lancer.
:banana:
A BASE Lancer? Good choice! Can't even get those with AWD.
 

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I had the same exact noise on my00 impreza obs 2.2l sohc, I thought it was piston slap at first. I put the car up on my lift took a stethoscope and listened around, the block itself was dead quiet on both sides so that minimized piston slap. I poked around some more and found the noise was potent around the timing cover. I took apart the timing covers took all the pulleys off and found that the t-belt tensioner had a small pool of oil sitting on the top indicating that it was loosing oil pressure and was bouncing around with the car running. I also took off every idle pulley and they all made a nice growl noise when spun in my hand. I ran over to autozone bought a timing pulley kit for $200 and the noise is good for good.
 

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I had the same exact noise on my00 impreza obs 2.2l sohc, I thought it was piston slap at first. I put the car up on my lift took a stethoscope and listened around, the block itself was dead quiet on both sides so that minimized piston slap. I poked around some more and found the noise was potent around the timing cover. I took apart the timing covers took all the pulleys off and found that the t-belt tensioner had a small pool of oil sitting on the top indicating that it was loosing oil pressure and was bouncing around with the car running. I also took off every idle pulley and they all made a nice growl noise when spun in my hand. I ran over to autozone bought a timing pulley kit for $200 and the noise is good for good.

Honestly if the OP's noise is actually piston slap (and the symptoms described fit it perfectly), then it was absolutely not the same noise. Piston slap is a dull and hollow thudding sound, not horribly dissimilar from rod knock (but with very different circumstances). A timing-related noise is going to be much sharper and clearer.
 

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Discussion Starter #15
A BASE Lancer? Good choice! Can't even get those with AWD.
No definitely not a base lancer. Those might be one of the ugliest cars ever made aside from the Aztek. I was looking into the Ralli Art versions that have AWD. Can't afford an Evo X yet and the IX and lower don't really suit my fancy. But I have always craved these crazy bug eyes! :projectsti.com:
 

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Discussion Starter #16
I had the same exact noise on my00 impreza obs 2.2l sohc, I thought it was piston slap at first. I put the car up on my lift took a stethoscope and listened around, the block itself was dead quiet on both sides so that minimized piston slap. I poked around some more and found the noise was potent around the timing cover. I took apart the timing covers took all the pulleys off and found that the t-belt tensioner had a small pool of oil sitting on the top indicating that it was loosing oil pressure and was bouncing around with the car running. I also took off every idle pulley and they all made a nice growl noise when spun in my hand. I ran over to autozone bought a timing pulley kit for $200 and the noise is good for good.
Trust me bro, I know what timing noises sound like. It's very easy to differentiate engine internal from external part noises (hence why I posted originally to try and figure out what internals could be making the noise). Definitely not that but thanks for the input anyway.
 

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No definitely not a base lancer. Those might be one of the ugliest cars ever made aside from the Aztek. I was looking into the Ralli Art versions that have AWD. Can't afford an Evo X yet and the IX and lower don't really suit my fancy. But I have always craved these crazy bug eyes! :projectsti.com:
Well, to each their own- I think the bugeye is just about the ugliest Impreza ever, and I'd rather have an EVO 8 or 9 over the X. Nothing wrong with any of them, just personal taste.
 

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Discussion Starter #18
Well, to each their own- I think the bugeye is just about the ugliest Impreza ever, and I'd rather have an EVO 8 or 9 over the X. Nothing wrong with any of them, just personal taste.
Is it because you prefer the 4G63 or is it the looks?
 

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Discussion Starter #20
It's the opposite of the Subaru- I actually prefer the looks of the X, but the 4G63 makes one hell of an argument against them.
So then I should get an X and drop in a Cosworth 4G63? :biglaugh:
 
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