126K miles now. Is there any particular mileage at which it would be
advisable to replace the struts? I'm not aware of any significant
problems, but any deterioration would have been very gradual and
probably not noticeable. Any way of testing?
I have replaced the two front struts and one rear strut on my '00 300m.
It has about 112k miles on it.
The rear strut was replaced because back in Dec. 2011 or Jan 2012 (I
forget exactly when) I hadn't yet put my snow tires on the back wheels,
and going down a slight hill with a slight bend I spun around and the
rear tire hit the curb flat-on and bent the rim (chrome Razor-Star
factory original) and bent the rear spindle down about 5 degrees. The
outer surface of the rim was deeply cracked for a few inches, but the
rim and tire remained air-tight. After the impact, that wheel continued
to turn true (no wobble) but the wheel/tire was riding on an angle
relative to true verticle (by about an inch at the top of the tire). I
continued to drive the car like that for almost a year (only
short-distance, inner city driving - nothing faster than 50 mph) until I
fixed it. It turns out that the bearing race had cracked, but the
cracked piece stayed put. I bought a new bearing, knuckle (with axle),
and quick strut. But I suspect that there was something wrong with that
strut before the impact.
To answer your question more directly...
One of my front struts failed some-what catastrophically this past Dec
24 - the day before a 100 mile highway drive to visit relatives. The
lower plate that the spring rides on had become detached from the
strut-tube due to rust, and the spring forced the plate into contact
with the steering arm and torsion-link arm located about 1 inch down the
tube. Those arms are very strong and prevented the plate from
contacting the tire (just barely). I bought a Monroe quick-strut that
day, and by 10 pm Dec 24 I had the new strut mounted and ready for the
drive the next morning.
About 2 months ago I replaced the other front strut because I noticed
that about half of the weld holding the lower plate to the strut tube
was basically gone - again due to rust.
So here's a picture of what a new strut looks like:
The lower spring-seat is the round plate under the spring. It is welded
to the strut tube. That weld is what will rust away. It will be easier
to see that weld if you jack up the front of the car and slide the
corrogated protector tube up to get a clear view of the weld.
My 300m has some surface rust along the bottom edge of some of the
doors, but otherwise I wouldn't have thought that there could be any
place on or under the car that would be suffering rust dammage to that
extent that I saw on those struts.
I've already replaced the front sway-bar links once a few years ago, and
the front sway bar bushings. During all this work I replaced the front
sway-bar bushings a second time - and found the new set to be too loose
so I had to modify them to fit better. I also replaced the rear sway
Since I still have a noticable knock in the front end, I'm going to
replace the lower control arms next, and the front tension-bar to frame
bushings while I'm at it.
At some point this year I'm also going to replace the front wheel
bearings, but those axle nuts are going to be a bitch to take off...