Mystery problem fixed itself. I am amaze!

I have a '98 e36 M3 built into a done-the-right-way mostly track car. I used it a lot for a few years but when I went wheel-to-wheel racing about 5 years ago I essentially stopped driving it. Recently I redid the interior, tidied it up and recommissioned it as a street car. It's great - makes lots of power, sounds fantastic, handles amazing. The inside looks and smells like new. It's a great car and it's stopped me from obsessively shopping for a Cayman S.

But for one thing.

It's had a suspension clunk. Or rather, KLUNK!. The suspension is AST4100 coilovers w/ Vorshlag camber plates/upper mounts. 550#F/625#R springs. All new bushings everywhere maybe 60 hours ago, every weld-in reinforcement possible. All the diff and trans bushings, giubo and center bearing same time. All the sway bar mounts and ends are perfect.

Straight line over a small speed bump, maybe a little clunk. hit a little ripple with one side but not the other? big clunk you can feel clearly. #1 suspect was loose top nuts or bad spherical bearing. Checked and torqued. All good. Tried removing a swaybar end link to take the sway bars out of the equation. No difference. Put a wrench on everything under the car. All tight. Try every damping adjustment. No change. I'd bought 4 new spherical bearings on the basis that the clunk could be felt both on compression and rebound but had yet to install them.

A couple days ago, I drive down my street which is a post-apocolyptic paving scape of ruts, heaves, patches and potholes.

No clunk. Silent compliance. I deliberately look for things I went out of my way to avoid prior; nothing.

Nothing ever really fixes itself. Religiously following this edict is a big part of why my race program has had zero DNFs. A symptom indicates a condition that must be remedied before continuing.

But I tried everything to pin this down, and I'm old and experienced and know this stuff cold. It was a bad interface between the damper and chassis, and there's exactly 8 places where it can be, and it can't "just get better".

Anyone else ever experience anything like this?

I drive a VW, Of course I encounter this on a daily basis. I got out of my car a few days ago, LEFT side parking lights stayed on.... well alright. start it drive around the block, never happened since! I love Euro cars

I wish my clunks on my Miata would fix themselves like that.

my e36 with AST4100's, vorshlag camber plates, and stiff springs like yours (might have even been stiffer by a bit) had a similar symptom.

I never figured it out, but I always thought it was something unrelated to the suspension loose and clunking. I did have a gutted car, so there were lots of buzzes and rattles in the interior. For example, maybe the hood hinge was loose or something and allowed the hood to bang down and up on a bigger bump. It couldn't have been a small part though, based on the noise. I was not nearly as thorough as you about the rest of the bushings though, so I might've had a wear problem somewhere else too.

If something was loose and rattling, maybe you dislodged it? (or stuck it tight?)

Problems that go away by themselves usually come back by themselves. Just saying. I have a mystery clunk in the right rear of the Manic Miata that never seems to be in remission very long.

Maybe an internal damper valve in a shock was stuck open, and finally decided to work right?

recently had a noise... not so much a clunk as a tadump. Looked everywhere. Then one day I was looking for the umpteenth time and while using my hand (soft fleshy part when you make a fist) I missed the lower control arm, and "bumped" the fuel and brake lines. they shifted... and I haven't heard the tadump since...

try other things under there besides the mounting points.........

Your battery landed crooked and jammed itself from clunking anymore! HooraY!

I bought a used car that had a mystery clunk. Turned out the rear brake caliper only had one of the two bolts it needed to stay attached to the pad carrier. It would randomly "fix" itself, as it wouldn't bounce loose during braking pressure. Never thought to look at the brakes for the source of the noise. Then did a brake service and noticed it.

how's your exhaust hung?

In reply to HappyAndy:

That's what I was thinking.

New factory hangers on the (Corsa, twin can) exhaust, all the way back. It can't hit anything. Battery is new and clamped down.

When it was doing it you'd feel a definite impact both when the suspension compressed and rebounded. The only things I know that do that are shock/strut mounts and swaybar mounts/end links.

Motor & transmission mounts look good? Any loose/heavy objects in the trunk?

motomoron wrote: New factory hangers on the (Corsa, twin can) exhaust, all the way back. It can't hit anything. Battery is new and clamped down. When it was doing it you'd feel a definite impact both when the suspension compressed and rebounded. The only things I know that do that are shock/strut mounts and swaybar mounts/end links.

check your front diff mount - the bolts have a tendency to shear off on the E36 when the rest of the driveline gets stiffened up and beat on at the track.

Giant Purple Snorklewacker wrote:

motomoron wrote: New factory hangers on the (Corsa, twin can) exhaust, all the way back. It can't hit anything. Battery is new and clamped down. When it was doing it you'd feel a definite impact both when the suspension compressed and rebounded. The only things I know that do that are shock/strut mounts and swaybar mounts/end links.

check your front diff mount - the bolts have a tendency to shear off on the E36 when the rest of the driveline gets stiffened up and beat on at the track.

BTDT. Faced the diff case flat and helicoiled it, new AKG front bushing and grade 10.9 bolt installed w/ red loctite, Rogue cover w/ new OEM BMW bushings.

Faced

Helicoiled (On purpose. Not Keen or Time serted)

W/ new bushing

Going back together

What ever was clunking fell off.

Or, or, or- rear shock mount finally tore all the way out? Debbie downer here, I hope not.

Dang. I have a clunk but I know what it is. I'm just poor (it's the Lca bushings, and I'm fixing it this winter)

I had a WRX that had a bad clunk in the rear. It never fixed itself, but it took me a year to find it. The threads on the shoulder bolts passing through the IPD rear sway bar had stretched, causing them to be sloppy even when they felt tight. I replaced them with Grade 8 bolts and the noise went away. The new bolts would only last a year, but at least it was an easy fix when the noise came back.

My e30 did that for a few weeks.turned out it was the jack In the trunk.it was just loose enough to clunk.

In reply to tjbell:

Park your car, leave the driver's side window down, get out and look at all the lights. Then reach in and push the turn signal stalk down and look again. Then try it up.