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mikeshoup

Rattling Maybe Knocking Sound?

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So my EA81T was running just fine today. Drove it for about a total of 15 miles today, came home parked it. Went out about 1.5 hours later, start the car, and this terrible racket is coming from under the hood. Something is rattling, rumbling, I can't figure it out.

 

Its sounds like a rumbling almost at idle. As the throttle is opened, the sound gets quieter until the throttle is closed, then the noise is really loud as the engine decelerates.

 

Its none of the accessories making noise. There's plenty of oil. Depressing the clutch pedal does not change the sound at all.

 

I'm kinda really at a loss here.

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wowzers!!!! that sounds NASTY! Have you checked all belt idlers or tensioners? is there a clutch fan on the motor? Have you removed the accessory drivebelt(s?) to check for shaft play in your alternator, PS pump, or anything else? I know you said "none of the accessories" but seriously.. if the engine isnt running poorly, I cant see that being valvetrain noise or serious crank/rod damage...

 

Can you localize the source of the noise at ALL? try using a piece of tubing in one ear, and block the other ear shut.. fish the tubing around and see if its louder in any areas....

 

It REALLY sounds like a fried fan clutch, or tensioner bearing.. but the bearing theory doesnt hold much water, as it would put a fairly decent load on the engine by seizing... is your engine effected by this "noise?"

 

Are you certain that depressing the clutch pedal is disengaging the clutch? clutch works fine, right?

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I removed the drivebelts, thus why I ruled out the accessories (I should have been a little more clear on that)

 

Clutch action works fine.

 

The noise is pretty loud, so I'm having trouble localizing it.

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My brother hears and believes it to be a turbo bearing, potentially. An idea to look at. The noise doesn't sound to be bad engine mojo.

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I agree but I don't want to get your hopes up. It wouldnt be hard to swap out the turbo to rule it out if you dont have a spare lying around lemme know, you can borrow the one off my coupe for testing if you wish.

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Does kinda sound like the turbo compressor wheel hitting the housing.Less noise w/more RPM suggests this too.IIRC,the compressor inlet is fairly easily removed to check for excessive play.

 

Consider a loose flywheel,suddenly sloppy disty/damaged drive gear and non-disengaging starter too.

 

After hearing it again,it sounds too loud to be the turbo.Sounds more like a foreign object caught between a piston and head.Seems like the noise might be at twice the frequency of the ticking valve.Hope I`m wrong.

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Try using a large screwdriver as a solid stethoscope, or a piece of tubing. Harbor Freight sells mechanic's stethoscopes fairly cheap..

 

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=41966

 

$5.99. This one, you could use both as an air-based stethoscope, for finding vacuum leaks, AND a solid, "touch it to the engine and find your noise" type scope.. I do not own one, but I have used one and I have used improvised "stethoscopes" more times than I can remember.

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Check to make sure nothing got caught in the bell housing and is rattling against the ring gear..had a bud (granted this was a wrx) the metal guard that is bolted to the bottom of the bell housing had bent slightly..so much so that the car was perfectly quiet when it was elevated but when u put it on all four the racket sounded almost exactly like that..bent the bracke straight with a screw driver problem solved..

 

could be the turbo bearings as others suggest, but I'm not hearing the delay I'd expect to hear after the throttle was closed and the engine idled back down, if the turbo had spun up it'd still be spinning down after the engine returned to idle..this sound is tracking engine rpm almost linearly..

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It does almost sound like the inspection plate grabbing on the flywheel. Did you put it back on when you did the 4spd swap?

 

Its not an engine related sound as I've known them. Rod knocks kinda sound like a midget with a ball peen hammer pecking, main knocks sound like a midget with a rubber mallot thumping.

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My loyale was making sounds like that the other week. My driver's side belt tensioner pully bolts were stripping out the threads inside the block. I got the belts tight and it started fine. I shut it off and tried it again and the same noise. The damn thing kept coming loose. I replaced the belts and put helicoils in there and all is well. I never owned a turbo before so i have no idea what a bad one sounds like.

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It can't be anything to do with the timing belt tensioners. (I have no timing belts :lol:)

 

My thought is something in the bell housing may have rattled loose. Like a flywheel bolt, or p-plate bolt. I don't remember anything about an inspection plate, though I'll look and see if that could be it too.

 

Turbo seems unlikely to me, because the noise matches the engine speed. There isn't any lag at all (which I think there would be?).

 

I'm off to Illinois for a week, so I'll tinker with it when I get back.

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Found the source:

 

All but one of the flywheel bolts were loose. I originally tightened 'em all down to specs on torque. My torque must not be all that accurate :(

 

This time, I'm gonna use loc-tite on them.

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