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Old 11-18-2005, 03:12 PM   #1
tfisher311
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1997 Legacy GT
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Default Engine rattle, clatter

I hate to do this b/c there are 100 threads about everyone's different engine noises. This is the last abnormal noise left on my car and I'm having trouble self diagnosing it. I really don't want to bring it to the shop until I've done everything I can to figure it out.

I hear a healthy clatter as the engine approaches 3k RPM, it happens running up through the gears and/or at cruise. The frequency is timed with the engine speed and is really timed perfectly with the exhaust pulses. I sounds more internally mechanical than a heat shield or loose part rattling. It only really happens under load (accelerating or climbing a hill) although it doesn't happen 100% of the time. Sometimes when it is happening, I can let off the throttle then reapply power and it will be gone. It doesn't correllate to engine temp at all. It happens hot and cold. My biggest issue with the noise is that I can't get it to happen unless I'm underway so it's hard to get my head under the hood at 35mph.

I've removed all the heat shields as they broke loose. There doesn't appear to be anything loose in the engine compartment that is capable of this noise.

I have some ideas about what this might be based on some research here but the symtoms don't match up with anything that I've read.

Any advice or thoughts would be great. Thanks.
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Old 11-18-2005, 09:14 PM   #2
big_jesus
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what engine? is this your 97 legacy?
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Old 11-21-2005, 10:32 AM   #3
tfisher311
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The engine is the NA 2.5L in a Legacy GT sedan. Stock except for no heat shields.

I took it from Boston to VT this past weekend and it ran great. It pulls great, cruises real smooth, no complaints; until the noise kicks in.

If I cruise at ~62MPH it puts the tach right around 3kRPM, sometimes I hear what could be described as a wrap. I can make it go away by letting off the gas. Then if I add power it's not there, until cruise speed around 60MPH is reached. It simply doesn't happen above 70MPH.

It's clearly in or very close to the engine since it's coming from under the hood and it is perfectly timed with the exhaust pulses. I know it's not valves or pistons since they make noise at cold start and go away when warm. This a much richer almost but not quite metallic wrap/clatter/rattle.

It killing me.
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Old 03-12-2008, 03:25 PM   #4
DC16A2
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Default Me too!

"I hear a healthy clatter as the engine approaches 3k RPM, it happens running up through the gears and/or at cruise. The frequency is timed with the engine speed and is really timed perfectly with the exhaust pulses. I sounds more internally mechanical than a heat shield or loose part rattling. It only really happens under load (accelerating or climbing a hill) although it doesn't happen 100% of the time. Sometimes when it is happening, I can let off the throttle then reapply power and it will be gone. It doesn't correlate to engine temp at all. It happens hot and cold. My biggest issue with the noise is that I can't get it to happen unless I'm underway so it's hard to get my head under the hood at 35mph."

I'm experiencing exactly as you have described, tfisher311, on my 2002 Impreza - Outback Sport. I don't know what our problem is, but it sounds like "valve clatter" from the research I've been doing on the internet. It's driving me nuts too.
-Dave
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Old 03-12-2008, 03:29 PM   #5
subikid
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exhaust leak?
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Old 03-12-2008, 03:33 PM   #6
subiesurfer
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if ure car has 6 stars on the front, expect rattles lol


cant help u out w this one but i know what ure going through, ive had a handful of rattle already on my 06
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Old 03-12-2008, 07:27 PM   #7
subikid
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Quote:
Originally Posted by subiesurfer View Post
if ure car has 6 stars on the front, expect rattles lol
atta way to be encouraging about our cars bud
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Old 03-14-2008, 12:14 PM   #8
DC16A2
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Default Still clattering..

I wonder if it's a failing pump or something inside the engine, or something belt driven, and so "pulses" along with applications of throttle. Going to have a friend sit behind the gas pedal over the weekend while I listen to the engine bay, maybe something needs lubrication.
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Old 03-14-2008, 02:09 PM   #9
yarrgh
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pop the hood and turn it on. stick a screwdriver to your ear and the other end to various parts of the engine. I've had a mysterious rattle for the past 6 months, it's rod knock on mine. happens right at startup then quits after 1 second or so. then comes back at 3K rpms or so. pretty bad after it's warm. the solution? new shortblock....for me anyway.
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Old 03-14-2008, 02:22 PM   #10
mslstixx
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I have been told that a certain amount of valve clatter is normal on Subaru engines; this may be what subiesurfer is referring to. This sounds similar to what my car does and my engine is completely fine (also a SOHC NA 2.5L).

I think is has something to do with spring loaded valves. Maybe the experts here can shed some light on this.
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Old 03-15-2008, 12:00 AM   #11
Tim Sanderson
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Tfisher, Do you know whether your car has hydraulic lash adjusters?

I'd like to see the results of a leakdown test.

Any cel's?
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Old 03-15-2008, 11:11 AM   #12
gtbensley
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Definitely try listening with a screw driver or something like that to the engine. It should give you some sort of idea if something is making noise in it. If its a rattle then it might be something on your exhaust. Mine had a complete crack around one of the welds. It rattled like hell until I figured out what was wrong with it and had a new one put on because it would not hold a new weld.
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Old 04-16-2008, 05:47 PM   #13
DC16A2
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Default Rattling sound fixed.

It was actually a loose heat shield. The guys at North Coast Subaru did a good job.
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Old 04-16-2008, 07:02 PM   #14
RaceFaceXC
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a blown out cat will make some noise... and i think of this because it will be most of the time but not always.
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