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Old 12-11-2012, 05:19 PM   #1
rickr01
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Default How to Tell Piston slap from Lifter Noise

So I've got a 2007 Impreza with 111000 well maintained miles on the clock. Its a 2.5 and I've run Mobil 1 5W-30 since new changed every 5k miles. Had new head gaskets timing belt and pullies and water pump installed around 85k miles.

Its kept in a heated garage at night. When starting the car cold if its in the garage or its in the summer, the engine is as quiet as a church mouse. However, when I start it after its been outside when the temps are below freezing, its quiet until I start to drive and you here what I assumed were just tappets clacking. Kind of a dull clack at higher rpms that increases with engine speed. It seems most pronounced in lower gears and slightly higher RPMs. In higher gears at lower RPMs its not really as noticable. It doesn't go away until the car has been driven for quite a few miles and is thoroughly heated up. Even when the car has been driven for 5 miles or so and the temp gauge shows fully warm, it still has that dull sounding tap when accelerating until it is completely warm and has been run a while. Again it doesn't do it if it is a cold start after being in the heated garage or in the summer time. I have two friends with two different opinions. One says he thinks its piston slap? I would have thought piston slap would be at any cold start, warmer or colder? The other said all older Subies have this lifter noise when cold. What are your thoughts? Any good mechanics care to give me some way to tell? Thanks
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Old 12-11-2012, 06:36 PM   #2
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Typically, piston slap goes away after the engine warms up due to heat expansion.

I may be mistaken, but you shouldn't have hydro lifters in your car being an 07, so you shouldn't have any lifter noise unless your valves are out of spec.
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Old 12-11-2012, 06:53 PM   #3
Counterfit
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It's sounds like you're giving a perfect description of piston slap.
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Old 12-11-2012, 07:42 PM   #4
rickr01
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Quote:
Originally Posted by Counterfit View Post
It's sounds like you're giving a perfect description of piston slap.

If its piston slap shouldn't I experience it whenever the car has sat over night then warm or cold outside? Is piston slap a sign that the engines on its way out?
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Old 12-11-2012, 07:45 PM   #5
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Subie motors in general can be a little noisy after the first 100k. It is usually related to the valvetrain in my experience. If you've never had your valves adjusted it is overdue at this point.

I don't think piston slap is all that common on stock pistons since they aren't forged and do not do a great deal of expansion.

Another option might be your timing belt tensioner especially if it was not replaced when the timing belt got done.

Hope you figure it out
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Old 12-11-2012, 07:52 PM   #6
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A little bit of piston slap is pretty normal on a stock motor on really cold starts. Just take it easy until it goes away.
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Old 12-11-2012, 09:02 PM   #7
cal_look_zero
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Quote:
Originally Posted by Counterfit View Post
A little bit of piston slap is pretty normal on a stock motor on really cold starts. Just take it easy until it goes away.
This. I only get slap below 30*F. And yes, stock pistons do it a lot, especially post 96 when Subaru shortened the piston skirts to lower rotating mass.
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Old 12-11-2012, 10:23 PM   #8
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Reciprocating. If your pistons rotate, you have a wrist pin issue.
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Old 12-12-2012, 01:07 AM   #9
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Glad someone else caught that.
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Old 12-12-2012, 06:51 AM   #10
rickr01
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Thanks Everyone! When I left my garage this morning, quiet as a church mouse. Last night in the cold before leaving for home let her idle for 5 minutes to warm up....no issues no noise!

Since it is more of a ticking and the ticking increases right along with RPM, I'm going to assume normal 100,000 mile lifter noise. It sounds very similar to the old fashioned non hydraulic solid lifters when the engine was cold.

Someone here said I am over due for a lifter adjustment? This is an 07. Doesn't it have Hydraulic lifters? Do they still require periodic adjustment in an 07 2.5 motor? Thanks Again for all the advice.
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Old 12-12-2012, 07:07 AM   #11
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I saw this clip a few months ago, should explain what's going on with your pistons
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Old 12-12-2012, 08:37 AM   #12
rickr01
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Quote:
Originally Posted by alt14 View Post
Subaru Piston and Rings - YouTube

I saw this clip a few months ago, should explain what's going on with your pistons
That was great information. Thank You very much!
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Old 12-12-2012, 06:20 PM   #13
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Not a problem, it made me feel a little better about it haha
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Old 12-15-2012, 07:37 PM   #14
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I can sleep a little more soundly at night now
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Old 12-18-2012, 12:31 PM   #15
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I was told my 07 impreza had "normal" noise for a subaru. All the valves were about 2x spec. The car gained power, fuel economy and hushed up A LOT. They are manually adjustable lifters. You have them too.

That said it still has light piston slap cold and eats oil, 75k miles.
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Old 12-18-2012, 02:54 PM   #16
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Quote:
Originally Posted by alt14 View Post
Subaru Piston and Rings - YouTube

I saw this clip a few months ago, should explain what's going on with your pistons
Thanks for posting that, help me understand a lot more with whats going on with my wifes car.
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