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Hello! I have a 2004 Honda Civic Si. It's got a issue that's been happening at least a year but maybe two where it rapidly clunks when turning moderarely-hard left at speeds above 20mph. It makes the same exact noise when going over bumps most times... But not always with bumps?
since it's onset I have replaced the front sway bar links and bushings using "high quality" parts(as the sellers would tell me). This has had no effect on the noise. The rear sway bar was removed from the car in its entirety before I bought it and therefore predates the onset of the clunking.
Only other information I have is that my left CV is leaking(according to a friend) and my steering doesn't return to center by itself. If I turn it right or left and let go it stays turned in either direction until I manually turn it back to center. It's done the steering thing ever since I bought it.

It also does this significantly more when there is someone sitting in the passenger seat. I'm assuming the weight does it. If I stop accelerating while Cornering it stops until I accelerate again.
Thanks!

 
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Oh and I wanted to note that the sound seems to be coming from all corners of the car. A different corner every time. This was my initial hearing and 5 or so people also say they hear it come from a different corner of the car every time. However, this may be just a auditory trick.
trick. It also sometimes vibrates the floorboard with each Clunk but that's rare.

 
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Jack the car up and wiggle + pry all the suspension components, give the cv joints a wiggle as well

 
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On both sides I'm assuming? Im not terribly confident id know what to do. Could you give any tips on what suspension component to check and/or how to do it? Or should I rather just check if anything wiggles/moves?

 
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Lots of videos on youtube, or pay a shop

 
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isn't the exhaust banging on suspension?

 
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That was one of the things I thought it could be, but I couldn't get it to Clunk at all while pushing/shoving it in all directions

 
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well, the suspension is in a different position when car on the ground and turning...

 
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I'm not sure about turning, but I did the movement check with the car completely on the ground. Is there something I'm missing?

 
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not sure on the hatch, but on the other models, exhaust curves and passes on top of rear arms.
I have a pretty thick rear antiroll bar, it was clunking against it. (Had to find a fart can that was not that loud to clear suspension, but than my suspension is modified)

so, just replace the rubber hangers and see if improves
cheapo try (painful to install)

 
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Ah gotcha. Well yea it does pass on top of the rear arms. However, I don't have a rear sway bar like I (hopefully) said in the original post. I do have a aftermarket exhaust but iirc it was doing this before I swapped the stock for aftermarket.

If you have any ideas on further testing the exhaust theory I'm very willing to do them, though. I love been told it's not by my mechanic friend, but I still swear it's the exhaust. It only happens when that rear passenger suspension is "loaded" downwards

 
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well, there is the top hats too, the spring could not be fully seated, etc...

but the rubber hangers are the cheapest to try

 
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On that rear passenger suspension you mean?

 
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both sides, when suspension gets lightly loaded (on the inside of corner) it could move more

 
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Hello! Me with the 2004 Civic Si(EP3) Hatchback again. For the past maybe 8 months I've had this rapid clunk.
I'm not sure when or how it started, but it only happens when I turn hard left or very, very hard right while going 25mph or faster. No clunk when turning while stationary. No clunk while wheels are straight except rarely when hitting bumps. Increasing speed doesn't make it clunk faster, but it does make it clunk louder. It does this same clunk twice when I hit a bump occasionally with wheels pointed straight.
Weight(a person) in the passenger seat makes the amount of steering required to create the clunk significantly less. The heaver the person the less the steering needed with a 230lb person needing very little left steering at 40mph to trigger it.

so far I've tried:
Left CV just replaced(was torn).
Rear sway bar removed entirely
Front sway bar links replaced and torqued to spec
Front sway bar bushings replaced
All four struts seem good
All four wheel bearings now good(front right replaced)
Any ideas?

EDIT: looks like I already posted about this issue a month ago here. Not sure how to delete, but this post does contain new information. Up to the mods if it stays. Sorry!

 
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Check balljoints, tie rods, control arm bushings

 
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Just documenting here in case someone in the future finds this: I found the issue. I had my tire change done at Walmart and they installed the large wheel balancer weights in the rear tires. I'm assuming the fact that I have no rear sway bar had a lot to do with it, but yea those were smack against the rear subframe whenever it "swung" towards either rear tire. Popped the weights off and hasn't happened since. 9 months for it to be something so strange... Thanks though guys!

 
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Wow, that is an unexpected cause...
Never would have guessed...

Glad you got it resolved!