I could use a little help diagnosing a problem with my autocross car. It's an e46 330i in D Stock with a swaybar and koni DA's that has been to two events a month for 2 years now. After last month's Evolution weekend, I've developed a large clunk on very hard cornering at the transition to throttle. I honestly can't tell decisively if it's from the front or rear of the car, but I'm suspecting front.

I've lifted the car and looked for obvious problems. I've looked for broken motor mounts or subframe cracks, looseness in the suspension, bad wheel bearings.

There are some other potentially associated mechanical problems. At the same school, I lost an ABS sensor, 1 RA1 and 3 V710's (all corded) and the muffler fell off the hangers. With some help, I put the muffler back on at the site and drove home on the 4 other badly worn but good enough tires. Now, the exhaust piping rattles on the subframe on idle.

If anyone can give some suggestions on where to begin diagnosing this clunk it would be appreciated.

Possibly the one of the swaybars binding under torsion, then popping loose.
Make sure that both top strut nuts are snug to prevent slop in the strut bushing area.

m

^^^ plus you might want to check out the RSM's my .02

Possibly the one of the swaybars binding under torsion, then popping loose.
Make sure that both top strut nuts are snug to prevent slop in the strut bushing area.

m

Thanks for the suggestion mmark. I checked the strut top nuts and they are unchanged since I originally hammered the pins out and added camber. If it's a swaybar binding issue, how can I solve it? Drop the sway and lubricate the bushings? Or is the binding at the end links? Maybe I'll drop the front swaybar off the car and see if I can replicate the noise.

^^^ plus you might want to check out the RSM's my .02

Another good suggestion, is a RSM failure something visible? I visually inspected the mounts and there is no cracking or deflection underneath or around the mount. It looked perfect, but I'll check again tonight.

Check to see if there are any dents in the hood insulation - if there are, you could have a broken motor mount. I killed my stock ones autoxing at bumpy Candlestick park...

Could it be the exhaust hitting the bottom of the car?

Time for new Front Control Arms. I believe those still mount the same way the E36 do. If so, I recently had a similar issue, turned out the Inner Ball joint on one side was quite lose, even though I thought I had checked it.

It started as a light clunk, that I couldn't tell where it was from, then I determined it was from the left front, I could load and unload the front corner, pushing or lifting and make it clunk.

I went through checked Camber Plates, Shock mounting points, swaybar links, etc, turned out to be inner Ball joint nut was lose.

I replaced the arms anyway, they were 1 1/2 years old with 2000+ track miles.

+1 for new control arms and ball joints. I discovered that my rear ball joints had failed a few weeks ago and were making a similar noise at the intial point of being thrown fairly hard into a turn. I had initially replaced the RTAB's that had popped out thinking that it was the cause of the issue.

I had a similar issue on my e36. I had set up an M3 sway and struts and my mechanic told me to do nothing more than to loosen the sway bar and physically move the bearings in the end links. Said they had a tendency to bind. Did just that, retorqued, no more pop or bump from the front end. Try that before you spend money...

I had a similar issue on my e36. I had set up an M3 sway and struts and my mechanic told me to do nothing more than to loosen the sway bar and physically move the bearings in the end links. Said they had a tendency to bind. Did just that, retorqued, no more pop or bump from the front end. Try that before you spend money...

^^^Just so, or add some molybdenum grease between the bar and the two central bushings.

m

Could it be the exhaust hitting the bottom of the car?

Doubt it, typically isnt a "loud chunking" noise...More of an annoying metallic sound.