superangrypenguin

Went to the dealer for an unrelated issue and as a result they thoroughly inspected the front suspension and informed me that nothing looked off.

Anyways, I was driving the car hard yesterday - lots of windy roads, and lots of WOT, and one of the things I noticed is that under hard braking and especially when turning the car, that there would often be a cracking/snapping sound. (I can also feel this through the brake pedal too, )

My only guess is that since I have the tires inflated at around 30psi or so in the front, that perhaps it's the rim making contact with the road, through the tire. If you want to scare yourself, turn the steering wheel when the car is parked all the way to the left or right and you'll see...it's freaky how flat the tire looks when you do that.

My only other guess is that it's a suspension related component - but that seems odd because of what I wrote in paragraph 1.

Thoughts?

Thank you

95Sinned420

Never have I ever heard of a rim hitting the road by hard braking, and I've had cars with really low profile tires.
Sounds like suspension related and perhaps even just the ABS pulsating back slightly? Even hitting bumps on low profile tires don't give feedback felt from the pedal, but just the car as a whole.

michail71

Ah, that reminded me. I had a knocking sound once with changes in momentum. Turned out to be something ABS related was loose. Right after they fixed that then I had a wheel speed sensor go bad. I'm not sure if those were related but it was the same wheel.

Funkwagen

Could be a failing CV joint/axle, those make snapping/thumping noises when turning usually

superangrypenguin

Thanks to all for your responses.

QQ: If this is a failing CV joint/axle, would this only occur under hard braking while turning?

I tested my vehicle today in a more controlled manner. If it's a hard fast turn, no problem. If it's aggressive stop in a straight line, no problem. If it's a hard fast turn while slamming on the brakes...problem appears.

michail71

If my memory is correct it sounds similar to what I had. I recall I could feel a knock on the brake pedal.

superangrypenguin

Thanks - the main issue is that the dealership is going to want me to reproduce the sound.

Short of driving like a maniac again I don't think I can. Any suggestions on what they can look for when the car is on a hoist or what I can do to reproduce it?

Thanks!

EDIT


Yeah, it does sound like this! (but only when driving like an insane man who has escaped from prison). Do you think it's just a sign of things to come? (car's under extended factory warranty so I don't care if I can't reproduce it right now)

michail71

They probably won't care if you're driving crazy as long as they get a warranty job out of it. It may just show up on a general inspection.

superangrypenguin

Fair point, but I also don't want to end up at the dealership without the ability to repro

Just for fun yesterday, I went to a school parking lot, and just cranked the steering wheel all the way to the left and drove it as hard as I could without drifting the damn thing - nothing - in either direction.

I also checked the CV boots on both sides, no leaks, no cracks, nothing.

Maybe i'll just wait and see if the issue gets worse and is easier to repro. No downsides in waiting since I still have warranty Thanks for the help tho!

superangrypenguin

Ok so I've repro'd the noise.

The noise can be caused by either doing an emergency swerve when traveling at a decent speed (60km/hr at least), or as per the video. Basically, when the suspension is at its full depression due to body roll, there's often, if not always a popping type of sound. (both left and right) One other example is say I'm racing up a mountain road when I'm doing a hard right/left turn as the vehicle is climbing up the mountain. As you can imagine, this would cause the "other side" of the car, while turning, to be fully compressed due to body roll. If you can imagine a chicane, hard left (pop), then hard right (pop), etc.

In a parking lot, I safely reproduced the sound. The sound can be heard at: clunk @ 3s 18s 36s

What's interesting to note is that the sound only occurs ONCE after the suspension is fully depressed on one side. Eg, hard left turn....then clunk...nothing. Then hard right turn...then clunk....then nothing. Rinse and repeat. My suspicion is that the part in question making this noise only makes this noise when it's fully compressed during one up/down cycle.

tekfoc

could be bad endlinks or bad center stabilizer bar bushings or bad control arm bushings.
you need to go under your car and move things around with a crow bar.

edgalang

After watching the video, my guess is that one of your sway bar end links need to be tightened. This is VERY similar to my previous car (where I replaced the sway bars), and over time, one of the sway bar end link nut that connects directly to the tip of the sway bar got loose and would shift when the bar is flexed.

The reason why I'm convinced is when you take a hard turn, the bar/bolt would adjust to 1 side (making a click/thud, essentially resetting itself), and from here it wouldn't make any more noise unless you shift the weight back in the other direction. Find the loose bolt/nut and tighten it a quarter of a turn (or go ahead and tighten them all since you're down there, just make sure you dont go hulk on it and strip it). You have 1 out of 4 chances to guess the right one...8 if you consider the other side of the endlink rod.

Bottome line, you can relax. The problem isn't as big as you think.

superangrypenguin

Thanks!

And dammit. I have extended warranty. Was hoping they replace thousands and thousands of $ worth of parts

Funkwagen

Definitely sounds more like sway bar links to me. I've gone through two sets of the things in under a year... both times I started getting this noise, but much worse. When I took the worn links out, the ball joints on the links had TONS of play - premature wear.

edgalang

...premature wear on endlinks? Sounds like your car loves running into potholes.

Funkwagen

Occasionally a pothole, but some roads around here are ridiculously rough, and they're getting worse over time

superangrypenguin

Took it to the dealer today and the shop foreman and I went for a drive.

I don't think he was impressed at my driving since I was asked to duplicate the noise.

Oops

But yes, I could duplicate it. Will be interesting to see what they say. If they say it's not covered under warranty and it's normal, I'm raising the issue with MB Canada because that's clearly insane if they say that.

Also drove two other W204 C classes tonight, and they did not demonstrate this same noise.

superangrypenguin

So they found..

Tear in one of the boots, so they're replacing one of the control arms.

Found a TIPS article on hydro mount bushings or something? Apparently the sound is as I describe it so they'll just replace that (not sure what that means).

They didn't find anything obvious.

superangrypenguin

This was what was replaced

Right front strut rod bushing
hydromount
elastomeric cup
hexagon nut
strut rod