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Old 10-05-2012, 01:30 AM   #1
pet3r
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Default Weird knocking sound

Car: 2008 STi, built block (CP pistons), every other bolt on imagineable

So, my car has driven perfectly the last 3k miles. I started hearing this knocking sound on Monday. Only driven it maybe 40 miles since then, but, it seems to be getting louder now. Car drives normal, acceleration is fine, idles perfectly.

However, tonight I pulled up to a light and the car died. I got a jump start, it started up and I was able to get to the next auto store and get a new battery. I put the new battery in and it couldn't start the car. Tow truck shows up, he jumps the car again. It'll run, but after a few seconds it'll die for no reason.

The knock is apparent after I let off the gas, usually only between 2200-4000rpm. Higher RPM I don't hear it. But, it's a loud sound, very obvious. If you let it idle, and lightly bring the RPMs up you'll hear it like in the video below.

I have a bad feeling about this one...but would love any thoughts on what it could be. The car was towed to a shop, and I forgot to check the oil before I dropped it off. I haven't had any oil consumption problems with the car, and it has been maybe 2000 miles since the last oil change, if that.

Video here: http://s1052.beta.photobucket.com/us...39a15.mp4.html
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Last edited by pet3r; 10-05-2012 at 01:52 AM.
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Old 10-05-2012, 04:26 AM   #2
Onnimanni
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Sounds like a bad rod knock
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Old 10-05-2012, 06:05 AM   #3
k04sti
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Either ur block wasn't built correctly or u had a poor tune u need to take it up with them. Post up your dyno sheet so we can see how it was running and if that looks fine then u got screwed on ur block. Sounds like rod knock
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Old 10-05-2012, 08:55 AM   #4
Leafy
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Sound like you need to go to your engine builder. I hope you have a 2nd car, because that baby is toast.
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Old 10-05-2012, 12:13 PM   #5
pet3r
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Gulp. Bought the car from someone else, the engine was rebuilt in 2010 by RAW Performance. Yep. Read about that guy. Don't think I'm gonna get anywhere with that.
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Old 10-05-2012, 02:30 PM   #6
MaddMax
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Rod knock
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Old 10-05-2012, 03:20 PM   #7
pet3r
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Yep. Rod knock combined with a blown main bearing. Oil starvation. I burned 3.5 quarts in just over 1000 miles. Lots of debris in the filter. Engine is toast
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Old 10-05-2012, 03:34 PM   #8
MaddMax
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Quote:
Originally Posted by pet3r View Post
Yep. Rod knock combined with a blown main bearing. Oil starvation. I burned 3.5 quarts in just over 1000 miles. Lots of debris in the filter. Engine is toast
Unfortunate. Was the car raced hard, over-revved, pushing significant power, or some other event that may have toasted the bearing? Luckily, the short blocks are relatively cheap and hopefully the pistons are salavagble.
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Old 10-05-2012, 04:39 PM   #9
UK-Wagon
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The engine shut off because the bearing was trying to seize at first. Jump staring it added more amperage than usual to the starter and thus it turned over. So essentially you made it worse but it was already damaged and the inevitable was coming.

A poorly built engine wont last 3k miles. So what ever happened was likely due to driving error or wrong oil of some sort, maybe the combo of both. Hard to say and likely wont ever know.
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Old 10-05-2012, 11:01 PM   #10
Baja_Gernaut
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I'll bet you never knew that car was burning oil and you ran it dry. If that engine lasted 2k then it was surviving but I really have a feeling you fell asleep on the wheel on checking oil consumption in a turbo charged vehicle. I also bet your heavy foot did not help the cause. Anyway, stick with a stock engine if you want to enjoy a good subaru. That's my .02. Sorry to hear that you have this heartache.
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Old 10-06-2012, 12:44 AM   #11
pet3r
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Sorry if I miscommunicated when the engine was built...it has over 18k on it, not 2k.
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Old 10-06-2012, 01:37 AM   #12
UK-Wagon
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Well, thats definitely operator error at that point....
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Old 10-06-2012, 11:07 AM   #13
meebs
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For the statistically minded... what brand and weight of oil did you use post rebuild?
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