When I take hard left turns, pretty much only when turning 90 degrees
onto a new street, I hear this "kwuk kwuk kwuk" in the back, kind of
like plastic bottles rolling around in the back of my car. If I'm going
faster, I tried through an intersection at 40mph or so the other day,
and the sound was similar but the pitch of each noise and the frequency
at which they occurred was higher (almost like a squeaking at that
point). I've driven the car maybe four or five times since it started
happening, hoping to get a chance to look underneath the car.
It /seems/ to be coming from the back right wheel, so I rolled that side
up onto a wheel ramp (to emulate a left turn) but couldn't see anything
that might be making contact with anything else. I took the wheel off,
and while there was a spot on the rim that looked like it /could/ be
rubbing somewhere (because it wasn't as dirty as the rest of the wheel),
but I couldn't find anything that it might be rubbing on. With the car
in neutral and the parking brake off, pulling on the wheel didn't
indicate to me that anything was loose, and it certainly didn't bind or
rub anywhere other than what I was getting from the brake pads.
So my initial thoughts were that maybe I needed to tear apart the wheel
bearings and grease them up, although looking at Performance Products'
online schematics makes it look like the bearings are possibly all
sealed and maintenance-free. So new bearings then? Looking at the CD
manual that I have, it looks like more of a job than I want to deal
with, not to mention I haven't got any sufficient pullers or any of that
jazz. I'd like to avoid the shop though, if I can; there's one local
not-dealer Mercedes shop, they seem to do good work, but they don't
entirely fill me with confidence.
I drove it today again, to get some planting soil, and the "hard" left
turns were accompanied by a sound more like an empty plastic bottle
rapping on the axle. Thinking more about it, I realized I forgot a
possibly-key bit of the puzzle in my last post.
A few weeks ago I replaced the oil in my hydropneumatic suspension.
Unfortunately, the manual seems to be missing a page, but I opened the
bleed screw, let everything drain out, then started the motor and let
even more drain out ('til the reservoir was barely empty), filled the
reservoir with clean and let it run, pumping out old oil 'til it was
clear. Then I ran the "go down" operation into another bucket (instead
of back into the reservoir) so I've got crystal-clear oil running
through the system's veins.
Anyway, realizing that this might be the "cause", I'm wondering, is
there a specific bleed operation I should do on this system? Just now,
I put the car up on wheel ramps and released the level controller from
the sway bar and operated the car for a couple of up-down cycles. It
goes up and down pretty fast, but when I let it down I hear a distinct
hissing like there's air going through the lines rather than oil.
However, given the design of the system, I was guessing (hoping) it
would be self-bleeding so I wouldn't really need to mess around with it
anymore. Operating this system by hand, it kind of sticks; it's not as
smooth as I'd like it to be, but I'm not excited about putting down $350
for a new level controller/distributor unit.
Anyway, I didn't get that same knocking sound when operating the system
by hand but it did definitely "clunk" (although not as loud as what I'm
complaining about) when changing the level controller from "raise" to
Any ideas? I'm thinking about taking this job to the dealer, at least
for diagnosis, but not sure how many of their mechanics have been there
for 20+ years and know anything about this system. ;)
Yeah the sound started a few days after I did the bleeding.
Sick of it, and not being able to see anything obvious with the car up
on a jack or wheel ramps, I went by the dealer. Oh yes, I guess I
didn't notice the sway bar just hanging there on the left side (I was
convinced it was on the right, so that's where I focused my attention).
So the coincidence is that I did the oil in the hydropneumatic system
and a few days later break (???) the sway bar connection on one wheel.
So it's all sorted now, and for $300 the dealer threw a full-car detail
on top of all new sway bar bushings, so I'd say it was money well spent.
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