Well in the interest of carrying on the conversation(s) about front end knocking, I got a set of those "chassis ears" and attached them all over the place. The problem is (at least with mine) is that each clamp is essentially a microphone, so you might be picking up noise from a rattling part, or from a part that is rattling right next to it. After multiple iterations of positions with the clamps, I felt pretty confident that it was the sway bar links. Replaced them today, still have the clunk/knock. Will have to do another round of "ear" clamping. I was suspicious that it was the rack bushings (based on eyeballing), but just didn't get much noise out of the rack assembly. Might be a strut--seems like the sound is less noticeable when in the raised position.

 

Following up, I saw that one of my rear shocks was leaking, and had the vehicle in the garage, and the mechanic said he thought my knock was coming from the driver side strut. So, I replaced the rear shocks and the entire shock/airbag assemblies in the front. Sure enough, once removed, the driver side front strut had noticeable play between the air spring and the shock (but so far I have been unable to disassemble it to see if it is just a loose nut, or something more nefarious). Anyway, that did the trick. No more knocking.

 

What. The sway bar is a monstrous U-shaped spring. Do you mean the clamps that hold the bushings? Or the little guide clamps that go on the bar? Or the links?

 

That fits with the noise becoming more frequent and higher pitched with the swaybar disconnected. The wheel is more free to deflect without the bar opposing its movement.

Good to know. Thanks for posting the results.

 

I meant sway bar links....

(original post edited for clarity.)

 

I know this post was from some time ago now, but I thought I would add my findings on my W164 ML500.
Before reading this forum, after investigating a knock getting progressively louder, but not occurring when the wheels were off the ground (on a hoist or jack), that the right hand steering rack mounting bush was absolutely stuffed. This occurred over about 5000klm while on a trip to central Australia, all was good for most of the trip, but the long drive home was an absolute fight as it was tracking really really badly. I also noted it was scrubbing tyres, and actually adjusted the ride height on one side a few hundred klm from home so it was running on a different part of the tyre, (tyres were buggered by that stage anyway, I just wanted them to get me home).
Anyway, after a few weeks of messing around looking for issue, I found the culprit last night. It was actually quite obvious with someone else yanking on the steering wheel while I was under car, (engine not running), as you could see the whole rack move back and forward up the right hand mounting bolt. As the car is right hand drive, the pinion is on that side of the rack putting an up/down pressure on that mount as well as a sideways pressure. The amount of movement is substantial, so as a result, I have no doubt that the right hand wheel would be changing the toe in as I drive it. Thus causing the tracking and tyre wear.
So in short, don't just dismiss a front end knock that is hard to find as a suspension issue, take a look at the steering rack mounts while it is on the ground with someone else turning the wheel back and forward.

Note: It also threw a steering angle fault at me about 2000Klm from home, but it wasn't tracking to badly at that stage, so as my cruise control wouldn't work with the fault present on the dash, I plugged my OBDII analyser in and reset it as it wasn't current, only stored. I'm pretty sure it was related, but to date this fault has not come back.
Cheers.

 

Thank you, Brett. That is good information to know about. I appreciate your taking the time to add this to the thread.