[Meca21000]

From my experience the knocking noise is from control arm bushings ... could be upper or lower. Since from the photos it looks like you purchased some bushings (with dust caps, no less!) I suggest you replace them. If you bought all four bushings, great. If you bought only two, I don't know if it's better to replace the uppers or lowers first. On my car I had to replace all four in order to completely get rid of the knocking noise.

Good observation :thumbsup:
Yes, this is upper bushing (goes into aluminum arm only).
Upper arms are aluminum, lower are iron.
I've just ordered the remaining bushings (lower and upper), as well as both sway bar bushings. I got a good deal on them, and my friend has press machine, so I though what the heck. We'll see, but I doubt it will change anything. In my opinion, it's something related to springs.

 

[jkowtko]

Well, after 10 years those need replacing anyway.

Now your struts don't look new -- have they been replaced yet?

If you friend has a shop press and not an on-the-car bushing removal tool, then you will need to pull out the control arms to change the bushing.

The lowers come out no problem, but with the uppers the ball joint is trapped by the lower mounting assembly of the strut, requiring you to unbolt the strut from the steering knuckly to make remove to remove the arm. This is a good time to replace struts since you are disturbing the mounting bolts (and the normal recommendation is to replace the bolts each time a strut is replaced)

 

[Meca21000]

Yes, both struts and rear shocks are new. Routes I go can get pretty muddy here, so they get dirty quickly.
He has a shop press.
We know we'll have to pull out the arms, but since struts are new, there's no reason to change them. Maybe something else you can think of ?
Even the strut holders are new, therefore strut bearings too (I think they come with holders in the same package).

 

[jkowtko]

The only issue is that MB recommends replacing the bolts whenever you unbolt the strut assembly from the steering knuckle. Especially that top bolt that you have to torque t o89 ft-lbs and then turn an additional quarter turn ... I don't know if they like that bolt to be torqued only once.

I can't think of anything else. There really isn't too much going on in these suspensions. Each part (control arm bushings, sway bar links, sway bar bushing, top strut mount) seems to have it's own sound associated with it. And the knocking sound goes with the control arm bushings.

Wait .. also check steering rack bushings. If you sense the knock occurs when going over small bumps or backing out of the driveway when wheels are turned, possibly it is a loose rack, or something in the rack. It's a different sound than the knocking while braking. I have this right now. My steering is still pretty tight and straight while driving, but I can hear/feel the looseness when going over a small height change when pulling into a driveway.

 

[Meca21000]

Uh-oh, now I don't know if that was replaced ever.
I'm a bit unsure if I know what you're thinking of - do you have a picture of those bolts that need replacing?

Also, is there supposed to be some kind of dampening rubber underneath or above the springs? Some cars have that, mine doesn't.

 

[jkowtko]

Uh-oh, now I don't know if that was replaced ever. I'm a bit unsure if I know what you're thinking of - do you have a picture of those bolts that need replacing?

The bolts I'm talking about are the three lower mounting bolts for the strut. Two bolt directly into the steering knuckle ... one of those you can see in your pic. The third bolt is the top thru-bolt that has a nut, and the bolt head is usually a hex. Those three bolts must be removed and the strut assembly pushed up a bit in order to remove the upper control arm from the steering knuckle.

Depending on what replacement strut you used, it may have come with a fresh set of bolts. If not, then when you remove the bolts to get the upper control arm out, you might consider replacing them at that time.

Also, is there supposed to be some kind of dampening rubber underneath or above the springs? Some cars have that, mine doesn't.

I had no rubber insulators. The strut bottom plate on my Bilsteins had a metal gulley where you place the end of the spring, and the "hat" on top had something similar. In both cases metal on metal. These springs have so much extension I don't think there will ever be a situation where unloading the suspension could allow the spring to move in its seat. I've heard of broken springs making noise, but not good ones.

 

[Meca21000]

Thanks.
I'm beginning to isolate a few things based on other users experiences (from other forum too).
Some of the things that cause knocking while turning the wheel are:

1. Tighten front wheel bearings (easy & stupid, but creates problems)
2. Steering rack bushings (4 of them, 2 upper, 2 lower)
3. Some cover above driver's feet that can loosen and touch steering rack (don't know yet what this is, I'll have to lift my car and check that out)
4. Your advice, strut bolts - I'll have to check them out too, because I don't know if they're new or tightened correctly.

 

[jkowtko]

Thanks.
Some of the things that cause knocking while turning the wheel are:

4. Your advice, strut bolts - I'll have to check them out too, because I don't know if they're new or tightened correctly.

The bolts are likely not loose or causing the noise ... but definitely check teir tightness just in case. Replacing them is mainly a safety issue (you don't want one of them to snap while you are driving the car).

 

[Meca21000]

Thanks.
I'm beginning to isolate a few things based on other users experiences (from other forum too).
Some of the things that cause knocking while turning the wheel are:

1. Tighten front wheel bearings (easy & stupid, but creates problems)
2. Steering rack bushings (4 of them, 2 upper, 2 lower)
3. Some cover above driver's feet that can loosen and touch steering rack (don't know yet what this is, I'll have to lift my car and check that out)
4. Your advice, strut bolts - I'll have to check them out too, because I don't know if they're new or tightened correctly.

OK, so finally, after a year, the problem is solved...
It was the steering rack bushings:

Besides them, we also changed all control arm bushings and sway bar bushings, the car feels very smooth now, like new!

Thanks everyone for the help, I really appreciate it. :thumbsup:

 

[300DFan]

Glad to hear it's finally fixed and thanks for the update. Oddly, even though I drive on spectacularly bad roads in Quebec I haven't had to replace those yet.

 

[Meca21000]

I guess you can't predict that. Once they're gone, they're gone. I purchased my car when it had 110k miles on it, who knows how previous owner treated it. All I know is that he had 18" wheels on it, maybe that shortened bushings' life too.