How to find a suspension noise when nothing is loose or broken?

I have a 96 Subaru Legacy that the drivers side front suspension is making annoying popping, clattering and banging noises but nothing is loose or broken, and it still drives fine. I have replaced most of the front suspension parts at least once to try to fix it and taken all of it apart to inspect the parts and put it back together and nothing is visibly wrong.  It's a bit concerning because especially driving on a washboard road it sounds and feels like someone under the car beating on the floor with a hammer.  Do I just ignore it because as far as I can tell all the parts that could cause a dangerous failure appear ok? It seems silly to get rid of the car just because it sounds bad but I don't think fixing it is possible because I can't find the problem.

Sorry didn't mean to double post but the site is having issues at the moment.

Swaybar

Motor mounts. 

Poly Bushings

Subframe bushings?

I have tried removing the swaybar for testing purposes and it makes no difference in the noise.  Both motor and transmission mounts are new factory ones with less than 10k miles on them.  It had poly control arm bushings and I took them off and put factory ones on (and new factory ball joints), and again no difference.  Tie rods, steering rack, cv shafts, the joint between the steering column and rack, new struts, and all the hardware for the struts including upper mounts made no difference.  The springs are king springs rather than the factory ones but I have taken them off and made sure they aren't cracked or broken.  It doesn't really have subframe bushings in the front, the rear ones have been replaced a few years ago.

In for ideas. I'm having this issue.

I've got a similar issue on my Jag that is so annoying it has basically stopped me from driving it. Low speed clunk on the driver's side. Replaced everything but the rack. I'm interested to see what your issue ends up being. Good luck.

Wire up some ChassisEARs?

And thinking something like this, but maybe there’s an HF version?

Jack it up and whack the tire with a BFH.  Isolate noise.

My suburban has this problem, and I still haven't been able to find it. 

That said, I've had a couple cars where suspension noises weren't suspension noises. On my silverado, the brake pedal arm/pivot is worn. Bumps will make the pedal bounce in a way that sounds like a failing sway bar link. If I rest a foot on it, no noise. Took me forever to figure out. 

One of my E30s is a late airbag car. There is a big gland nut on the column that allows the column to collapse in a wreck. They're notorious for making a thunking noise when driving that's really hard to recreate stationary. Does the Legacy have something similar? 

The 924 has a plastic spacer in one of the upper column bearings. Mine disintegrated, and while there was no excessive play that I could feel, it rattled on bumpy roads like a bad tie rod and could feel it in my hands. Similar story - whole new front suspension (it was nearly due anyway) but that stupid spacer bushing is what fixed it. 

Hopefully one of these things provides a burst of inspiration. I hate unsolvable clunks and rattles.

The car has very high mileage (546k) and still has the original steering column, so it's entirely possible part of it could be worn.  I can feel the clunk with my left foot on the floor too.  

It doesn't appear to be related to the brakes, because I can lightly press the brake pedal and it still makes the same noise.  It's definitely only related to the driver's side front, because on a washboard road I can line up the driver's side with the toughest part and it sounds like someone beating the floor with a sledgehammer, then put the drivers side in a smooth part and the passenger side in the rough part and it's quiet.

I definitely think I need to look harder at the steering column but it doesn't have any noticable issues otherwise.

How about the steering gearbox?  Either loose, or something worn inside?  Either could make a clunking noise on either bumps or steering, and either could transfer the feeling to the steering column or driver's side floorboards. 

SV reX said:

How about the steering gearbox?  Either loose, or something worn inside?  Either could make a clunking noise on either bumps or steering, and either could transfer the feeling to the steering column or driver's side floorboards. 

I replaced the rack with another used one and it didn't seem to make any difference. It's not that hard to change so I could try another one, it does seem likely, but it's really hard to tell.

Another idea...

Age could be a factor. With 546K worth of use, there are no guarantees that you are working with OEM parts. (Or maybe worse if you are!)
 

It's common (for example) for people to swap Legacy struts with Outback struts to try to lower the car a bit. This can conflict with the wheel or tire (and people don't always think about wheels, tire sizes, and offsets when they make suspension changes). Some Subie wheels have 48mm offset.  Some have 55mm. 
 

You said it was a problem on washboard roads. That means it could be anywhere in the full range of the suspension (including full droop and sitting on the bump stops).  Make sure you look at everything through the ENTIRE range of motion (not just the static condition).

It could be something that wasn't a problem 200K miles ago, but now the springs are a bit more fatigued and the car sits differently than it used to. 

You've done a lot of work to that front end. You didn't really say which parts are new, which are used, or which are "upgraded".

When you replace a part, do you match the part number to the old part that was on the car, or check the specs for the proper part number that SHOULD HAVE been on the car?

Subie owners like to switch parts. 
 

Are you confident you got the stack right when assembling the struts and mounts?  Is the diameter of the springs the same?  Do they seat well in the mounts through the entire range of motion?

Have you owned the car for most of its life, or were the first 400K with various other owners?

Does the clunking change when you turn to the right or the left, or remain constant when going straight or turning?

Did the noises begin after you made a change, or did they develop by themselves over time without any changes to the suspension?

Had the car since 150k, wheels are original, struts are new outback struts from rock auto, springs are king springs that lift the car about an inch (but they were on the car before this was a problem), I swapped the control arms with no change in the noise, but what is currently on there is OEM rear bushings and ball joints (new) and one factory and one aftermarket control arm I took from a turbo Baja because it used the same part number.  The other parts on the struts are new factory parts with the sti upoer mounts.  I think this issue first started a while after putting whiteline camber plates on and it worked for a while with no problem then started making a loud pop when I turned the steering wheel.  That appeared to be the bearings in the camber plates failing because they replaced them under warranty and it was fine for a while then started making noise again.  Axles are remanufactured from the dealer, but I tried a set of different axles (the ones for lifted cars from Rock Auto, which I removed because they are junk, but that was a separate issue).  The engine is a 1998 ej22 phase 1 with solid lifters (it came with the hydraulic lifter version), and the transmission is from a later Forester because it's the only one I could find that wasn't leaking from the case warping and breaking the seal form tightening the drain plug.  Brakes are original except for Carbotech pads and raybestos rotors.

In reply to Tk8398 :

I'd be looking at those camber plates again. 
 

Because of the caster, the pivot angle through the bearing on the camber plates can vary through the range of motion and bind.  You already had a set with bad bearings. Add some wear from 576k miles on other components, and it's possible the bearings didn't last long. 

I think you may have a mis-match in front suspension parts.  As I understand it, you've got...

A 1996 Legacy with:

- New Outback struts,

- King springs with 1" lift (are these overload rally springs?),

- STI upper mounts, and

- Whiteline camber plates.

I think the OB strut body is taller (2.82"), but the stroke is shorter (1.07").  Then there is a 1" lift and stiffer springs. Not sure how the STI upper mounts and the camber plates then play with everything. 
 

Is it possible the combination of the various parts is not allowing free movement through the range of motion and wearing out the bearings in the camber plates prematurely?  
 

Binding bearings in the camber plates would give symptoms like you are describing. 

Don't forget to inspect exhaust for knocking into chassis. I have had exhausts make  weird noise clunks before.   

The camber plates are basically strut mounts with the bearing offset.  I took them off and put the STI ones back on which are basically the same as the stock ones, just stiffer.  Right now the front suspension is stock except for the springs and aftermarket swaybar end links.  The noise is for sure not the swaybar because I completely removed it to see if that was causing an issue and it did not change anything.