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Old 08-26-2021, 07:29 PM   #1
a5m
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Default Rattle at Idle

Been hearing a erratic rattle at idle for the past month or so. Sometimes itís louder than other times, and sometimes barely audible or noticeable. Could hear it in the interior today with windows up.

If I put it in 1st it goes away. Leaning down by either of the front wheels I can hear it and sounds nearby, like underneath the car.

Any ideas what this could be?
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Old 08-26-2021, 07:58 PM   #2
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Exhaust heat shield
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Old 08-26-2021, 08:02 PM   #3
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Rocks in the miffler
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Old 08-26-2021, 08:02 PM   #4
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Broken turbine
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Old 08-26-2021, 08:24 PM   #5
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Have you done anything to the car recently that may have caused the rattle to come up? Can you post a vid of the rattle so we have an idea of what the issue might be? Do you feel it in the clutch pedal? Any additional info might be helpful
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Old 08-26-2021, 08:45 PM   #6
a5m
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Thanks to those trying to help.

Quote:
Originally Posted by snow_bound26 View Post
Exhaust heat shield
This crossed my mind too. But why does it go away when in gear? Will take a look anyway next time Iím under there.

Quote:
Originally Posted by neededatuna View Post
Have you done anything to the car recently that may have caused the rattle to come up? Can you post a vid of the rattle so we have an idea of what the issue might be? Do you feel it in the clutch pedal? Any additional info might be helpful
I wanted to take a vid but of course when I got home it wasnít there anymore. Will try and get one though tomorrow.

Donít feel it in the pedal. Canít think of anything that would contribute to that noise. Did the suspension recently. Maybe something got looser due to firmer ride? I changed all the shifter bushings back in January. Again, it goes away when going into gear so makes me think itís something else.
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Old 08-26-2021, 09:14 PM   #7
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Quote:
Don't feel it in the pedal. Can't think of anything that would contribute to that noise. Did the suspension recently. Maybe something got looser due to firmer ride? I changed all the shifter bushings back in January. Again, it goes away when going into gear so makes me think it's something else.

Not feeling it in the pedal makes me feel like it's not drivetrain related, but that's not a guarantee. Just to be clear, you no longer hear the noise when you engage first gear or as you're driving in first gear? That info alone will make a difference in what we may be able to contribute the noise to be.



If you did suspension work recently, it's possible that has something to do with it. But if can hear the noise at a standstill, it's likely not suspension related.



The more info the better with these types of things. I can't tell you how many customer's come in and say they hear and noise but have no information for us. Like does it happen at idle? Only while doing 55? These types of things make it difficult for even a Technician to accurately diagnose an issue at a dealership. The more info the better. I don't mean to sound harsh, I'm just being blunt. It's even more difficult when you're trying to help someone over the internet without any sort of evidence of the noise. A trained ear can hear a noise and identify what the noise might be. Me, not so much with these cars. I only learn about certain things when it comes up as an issue. For example, when replacing the clutch recently, I didn't know the turbo had to be either removed or lifted out of the way. If this we're a BMW for me, I might be of more help. I was a Technician for almost a decade, and still help certain technicians in our shop when it comes up that they are having issues with diagnosing a vehicle. But with Subaru, I'm fairly new. I diagnose and repair my own WRX but I am by no means experienced with how they operate, specifically compared to other manufacturers. But I will offer as much advice for you as possible while you try to diagnose what the issue may be.
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Old 08-26-2021, 09:28 PM   #8
a5m
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Quote:
Originally Posted by neededatuna View Post
Not feeling it in the pedal makes me feel like it's not drivetrain related, but that's not a guarantee. Just to be clear, you no longer hear the noise when you engage first gear or as you're driving in first gear? That info alone will make a difference in what we may be able to contribute the noise to be.



If you did suspension work recently, it's possible that has something to do with it. But if can hear the noise at a standstill, it's likely not suspension related.



The more info the better with these types of things. I can't tell you how many customer's come in and say they hear and noise but have no information for us. Like does it happen at idle? Only while doing 55? These types of things make it difficult for even a Technician to accurately diagnose an issue at a dealership. The more info the better. I don't mean to sound harsh, I'm just being blunt. It's even more difficult when you're trying to help someone over the internet without any sort of evidence of the noise. A trained ear can hear a noise and identify what the noise might be. Me, not so much. If this we're a BMW for me, I might be of more help. But with Subaru, I'm fairly new. I diagnose and repair my own Subaru but I am by no means experienced with how they operate. But I will offer as much advice for you as possible while you try to diagnose what he issue may be.
Not at all I totally understand where youíre coming from and know youíre only trying to help. I really appreciate that

Yes so as soon as I put it into first the sound goes away, before even releasing the clutch. While driving I donít hear it at all. Sometimes itís loud enough where as Iím approaching the car I can hear it from a meter or so away.

I noticed it when getting in and out of the car. Itís definitely somewhere towards the front. When itís making the sound at idle, even the slightest increase in RPM makes it go away (or the exhaust masks it but I donít think so). In the cabin I can hear it coming from what seems somewhere around the center console area. Itís been really hot so have been running the AC and with the windows up I could clearly hear it in the interior today.

I only really started trying to figure out whatís going on today. So I can try and check a few more things to diagnose and double check what Iíve already observed.

Thanks again for the help. I think a video will help narrow it down immensely. Iíll hopefully have that tomorrow.
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Old 08-27-2021, 07:03 AM   #9
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When you're idling in neutral with the clutch pedal released (i.e. not on the floor) the transmission input shaft and layshaft are spinning with the flywheel. When you press the clutch pedal and put it in gear, the clutch disc, input shaft and layshaft stop rotating.

So if the noise disappears at this time it might be coming from the transmission.

Because the gearbox is unloaded it's possible some of the noise you're hearing is normal cumulative gear backlash as the many gears sort of bounce off one another with the engine turning at idle. Having said that, I've never noticed a rattle from mine (though it does make a hell of a racket when slowing down in 2nd gear but it has always done that...) so your sound might be indicative of, say, a problem in the input shaft bearing, layshaft bearing(s) etc.

How's the transmission fluid level?
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Old 08-27-2021, 10:30 AM   #10
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its cancer...just like webmd, theres all the little things then cancer...sorry bro...jk lol, prob heat shield or loose plastic...listen around the car zero in on it to locate
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Old 08-27-2021, 12:04 PM   #11
a5m
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Quote:
Originally Posted by Blackfin View Post
When you're idling in neutral with the clutch pedal released (i.e. not on the floor) the transmission input shaft and layshaft are spinning with the flywheel. When you press the clutch pedal and put it in gear, the clutch disc, input shaft and layshaft stop rotating.

So if the noise disappears at this time it might be coming from the transmission.

Because the gearbox is unloaded it's possible some of the noise you're hearing is normal cumulative gear backlash as the many gears sort of bounce off one another with the engine turning at idle. Having said that, I've never noticed a rattle from mine (though it does make a hell of a racket when slowing down in 2nd gear but it has always done that...) so your sound might be indicative of, say, a problem in the input shaft bearing, layshaft bearing(s) etc.

How's the transmission fluid level?
Thanks for the explanation, that helped a lot. This is what Iím fearing as well. Did as much reading as I could and watched as many YouTube videos I can find that sounded similar and input shaft bearing seems to be the culprit. Either that or a heat shield or something that stops vibrating once the clutch is disengaged as you described.

Checked fluid about a 1000 miles ago after driving a while and sitting for about 10 minutes and the level was right at the ĎFí hole on the gauge.

Quote:
Originally Posted by Jedi03 View Post
its cancer...just like webmd, theres all the little things then cancer...sorry bro...jk lol, prob heat shield or loose plastic...listen around the car zero in on it to locate
Lol yea going to grab some ramps today and get under there and see where itís coming from. Really hoping itís the exhaust or heat shield or something.
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Old 08-27-2021, 03:11 PM   #12
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Just to clarify: The noise doesn't go away when you merely depress the clutch does it? That is, you need to put the transmission in gear and then it goes away?
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Old 08-27-2021, 04:29 PM   #13
a5m
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Quote:
Originally Posted by Blackfin View Post
Just to clarify: The noise doesn't go away when you merely depress the clutch does it? That is, you need to put the transmission in gear and then it goes away?
I couldnít remember exactly from yesterday but I tested again today and the sound goes away once the clutch is depressed all the way without putting it in gear. Pressing it half way or even 3/4 the sound is still present.

Right after this as it was still idling I turned the AC on for 5 minutes and after turning it off I couldnít hear it at all.

It wasnít very loud today so I couldnít get it on video. All you hear is the engine. When decelerating in 2nd, after trying to filter out the racket made by the diff, I thought I could hear it there too as it was approaching 1k.

Iím with my parents and itís hot as balls so will pick up on this tomorrow. Thanks again for the help.
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Old 08-27-2021, 09:20 PM   #14
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Quote:
Originally Posted by a5m View Post
I couldnít remember exactly from yesterday but I tested again today and the sound goes away once the clutch is depressed all the way without putting it in gear. Pressing it half way or even 3/4 the sound is still present.
So two other possibilities that came to mind re the clutch were:

- the release ("throwout") bearing possibly rattling with the clutch pedal released (so the bearing unloaded), and

- the crankshaft thrust bearing in the engine. It bears the full force of the springs behind the clutch cover that force the pressure plate to sandwich the disc. If it's worn the crank could be "walking" back and forth due to the excessive clearance.
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Old 08-27-2021, 09:52 PM   #15
a5m
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Quote:
Originally Posted by Blackfin View Post
So two other possibilities that came to mind re the clutch were:

- the release ("throwout") bearing possibly rattling with the clutch pedal released (so the bearing unloaded), and

- the crankshaft thrust bearing in the engine. It bears the full force of the springs behind the clutch cover that force the pressure plate to sandwich the disc. If it's worn the crank could be "walking" back and forth due to the excessive clearance.
Man this is getting worse and worse. Thank you so much though for helping diagnosis.

All the videos I watched of TOB nose sounded more of like a whine or hum. Not saying itís not possible. Saw a ghetto spring trick to sort that out which Iíd be happy to live with if it works.

What are the chances I get under there and itís just a loose heat shield or something? Would the above cause the sound to be intermittent and varying in intensity/presence? I gotta get a video first and narrow down the source.
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Old 08-28-2021, 03:40 PM   #16
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Quote:
Originally Posted by a5m View Post
What are the chances I get under there and itís just a loose heat shield or something? Would the above cause the sound to be intermittent and varying in intensity/presence? I gotta get a video first and narrow down the source.
Definitely check the low-hanging fruit first before opening anything up.

Buy a mechanics stethoscope if you can't locate a simple rattling heatshield to try to locate the exact position of the noise.
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Old 08-29-2021, 02:50 PM   #17
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Quote:
Originally Posted by Blackfin View Post
Definitely check the low-hanging fruit first before opening anything up.

Buy a mechanics stethoscope if you can't locate a simple rattling heatshield to try to locate the exact position of the noise.
Thanks good idea. Got the ramps yesterday (didnít need them, just wanted them) but worked late and it got dark already. Itís raining all day today. So tomorrow hopefully.

May also check my fuel pressures. Iíve read some of the fuel components can tick and be loud. But thatís for another issue Iíve been chasing.
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Old 08-29-2021, 05:23 PM   #18
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Second checking heat shield above cat etc
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Old 08-29-2021, 09:57 PM   #19
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+1 for exhaust heat shield
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Old 08-30-2021, 09:55 PM   #20
a5m
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Quote:
Originally Posted by mluedemann View Post
Second checking heat shield above cat etc
Quote:
Originally Posted by atliensubie View Post
+1 for exhaust heat shield
Thanks for the suggestions fellas.

So got under there today. Car wasnít in the mood to make the sound today I guess. Couldnít hear anything. Tapped on all the heatshields and anything else I could think of. Nothing. Only thing was the spring bolt on the exhaust where it mates to the downpipe. When I installed the catback one of those bolts was at an angle and resting against the piping. If I tried moving it itíd Ďflickí and make a ding, but not the same as what I was hearing. Maybe itís moving more subtly due to engine vibrations and the metal expanding due to heat under driving conditions? As it cools and contracts the sound goes away?

Also checked fluids today and the trans was 1-2mm below the ĎFí hole. Iíll add the little bit I had left over and see if that changes anything. Hope the correct way to check fluid is when warm, or else I may have been doing damage running it low :/
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Old 09-06-2021, 01:02 AM   #21
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Throw out bearing

Not a permanent fix,
But
There are some adjustment screws on clutch pedal
Under the dash, where pedals are located
I did the same until I saved enough $ for a clutch assembly
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Old 09-08-2021, 01:07 PM   #22
a5m
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Quote:
Originally Posted by AliBenn View Post
Throw out bearing

Not a permanent fix,
But
There are some adjustment screws on clutch pedal
Under the dash, where pedals are located
I did the same until I saved enough $ for a clutch assembly
Thanks. Thatís what the consensus seems to be. Iíll try some of those fixes and see if it goes away until I eventually replace the clutch.
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