After searching the forum and doing enough self diagnosis, I'm hoping to get your take on a minor issue on my LS430. I understand diagnosing noises via a forum is difficult, but maybe someone had a similar experience with theirs.

I have a 2005 LS430 with 95k miles. It makes a hollow noise/clunk in the passenger rear area.
- It only happens when going over harsh unevenness (road plates, manhole covers, potholes, etc.) at low to mid speeds (20 - 50mph)
- There are no noises when turning, on smooth roads, bumps that aren't as harsh as those listed above, low speeds, or high speeds
- Noise happens whether windows are up or down, so I don't believe it is a door or window alignment issue

This is the maintenance work that has been done to date (all in last 5k miles):
- New Struts (All 4)
- New Upper Control Arms (All 4)
- New Sway Bar Endlinks and Body Bushings (All 4)
- New Door Weatherstrips (All 4)

Here is the other work I've done to diagnose since the maintenance work:
- Checked torque on all suspension parts, and tightened to OEM specs
- Checked underneath for anything else that could be loose (heat shields, rear subframe, trans mount, diff mount, exhaust hangar, etc.). Nothing appeared out of spec

Other things to note:
- When I checked the top strut bolts, I noticed the car doesn't have the OEM shock caps. Do they have any performance impact, or is it purely aesthetic?
- I have not checked the brakes to see if there's any issue with the hardware. From the descriptions I've seen in searching the forum, that seems like a much different/louder noise than what I'm hearing.

What is really throwing me off is the narrow range (both speed and road conditions) in which the problem exists. That makes me believe it isn't a bad strut mount, bad spring, or fault new strut. Any help would be greatly appreciated. Thanks in advance!

 

I would guess it's a defective or improperly installed rear strut mount. Second guess would be faulty rear sway bar end links.

 

Can you have someone drive and you sit in the back and listen? Try moving from the left to right. Might go away with your weight on the right, which would point to the strut mount. Take a pry bar and check again for any play in bushings. Also check that nothing is loose in the trunk, spare tire, jack, etc.

 

Sometimes using a cheap stethoscope can help localise the noise.
It's surprising how useful they can be for things like that.
It does look weird though <LOL>

 

My mechanic inspected the strut mounts when installing the new struts and didn't see anything wrong with either of them. A faulty sway bar end link is possible... they are replacements from Moog, so maybe I'll buy the closeout Raybestos one from RockAuto as cheap insurance/test.

I forgot to mention in my original post that I did remove the spare tools, etc. from the trunk during this process. The spare is still installed, but tight. I'll check all other fittings back there, but don't see any other potential issues inside the trunk.

I haven't sat back there myself for a driving test, but have had weight back there to test... no change in noise. Will try it with a person as well to see if it changes.

Hah that's a great point! While the noise isn't nearly as bad as it was before the suspension work (the original struts and end links were pretty worn out), I'd be willing to have a few moments of awkwardness to solve the problem.

 

My first thought when reading your description is sway links

 

Thanks! I bought the closeout Raybestos right rear end link to test if the Moog replacements are faulty.

If they arrive on Saturday as scheduled, I'll install this weekend and let everyone know the results!

 

What brand of struts were installed? It could be a defective strut, but my money is still on the strut mount. My car makes the same noise under the same circumstances and I know for a fact the strut is blown. It's leaking oil. My '05 had the same noise/issue.

 

They're from Monroe. I did Quickstruts on the front and struts with stock springs on the rear since Quickstruts weren't available.

While it could be the strut mount, my mechanic inspected them and saw no issues/damage that justified replacement. Redoing the passenger side end links is way cheaper and easier than the strut mount.

 

I found a hissing noise in the rear passenger area today. It turned out to be my mother-in-law.

 

Hah luckily I don't have to deal with one of those.

Quick update: swapped the passenger side sway bar end link this weekend and it seems to have fixed the issue!