bobinyelm

2003 C320 Wagon with 88,000mi



This was my vehicle for 8 years and I just sold it to an acquaintance. It's been flawless, but suddenly is making a LOUD creaking sound whenever the right rear suspension is flexed even as little as 1/4", but does it over the full range of suspension travel as well.



The car is an always-garaged pristine-no rust (never driven on winter, seldom in rain or on wet roads, and never on dirt) and one could safely eat off the entire underside of the car and suspension. The bushings are tight w/o cracks in any rubber components. I mention this to suggest that corrosion or damage would be unlikely (though he admits to driving into a shallow ditch right after buying the car and had to get it pulled off a soil berm, but visually I/we can see no damage, and there are no scratches and no dirt present anywhere on the suspension from the encounter).



I put the car on my 2 post service lift and lifting/lowering it a few inches with a foot of solid wood under the rear brake rotor hat (which allows the suspension to compresses/decompresses only the LR suspension) produces an almost deafening creaking sound in both up and down directions (not unlike one would expect to hear in a really low budget **** film of two "active" people in a cheap motel bed). I soaked everything capable of flexing or moving first with silicone spray and then WD40 with no change at all, and a hand placed on the inner end of the lower control arm (near the bushing) can feel the vibration of the creaking, as can a hand placed on the spring. I loosened the bushing center through-bolt and rotated it while injecting oil so flexing the suspension only caused the bushing's center metal bushing toi rotate on the bolt without flexing the rubber portion) and the noise was the same. Prying up on the spring coil using a pry bar against the control arm (near the spring seat) reproduces the abbreviated sound and vibration with no flexing of the suspension itself, reinforcing the idea that it's not likely a bushing. Prying actually flexes the stamped/welded control arm visually (surprising to me) but it appears to be formed of rather thin sheet metal, so I guess some flexing may be normal.



I was wondering if anyone has had such an instance and has an idea. I suppose it could be a not-visible broken spot weld on the lower control arm near the .inner bushing carrier, but if so it's not obvious.



Ideas solicited!



Bob

slammer111

Check the obvious stuff first. Without hearing the sound it could be anybody's guess. Personally I'd look at the strut first, then the control arm and sway bar bushings.

bobinyelm

No vibration at all felt on the rear shock absorber.

The noise is only from the LR side.

No vibration felt at the outer(outboard) control arm bushing (under the hub).

Vibration felt with a hand placed on the inner end of the control arm. Suspected bushing so loosened bushing through-bolt, oiled it so it rotated easily. No difference in the sound/vibration.

Using a pry bar resting on the rear side of the control arm and raising a spring coil 3/8" reproduces the sound (and can be felt in the spring and the inner end of the control arm, even though the
suspension itself is not moving at all (so no movement in any bushing or shock-just the spring).

None of the trailing/upper suspension arms have any feel of the vibration producing the noise.

The noise is loud enough to be heard 50ft from the car if the suspension is flexed even 1/2" by pulling the roof rack down over the LR wheel.

Started suddenly according to the buyer of my car (shortly after an off-road excursion).

No evidence of physical damage due to the ditch it entered-not even a scratch in the paint on any under-car component.

slammer111

Maybe try removing the spring then working the suspension. Is the spring broken at the ends? Also I would check the shock.

bobinyelm

You can "feel" the creaking when it makes the noise, and it cannot be felt at any points but the spring and the inner bushing on the lower link/control arm.

Levering the spring up a bit with the suspension hanging all the way down (on a lift) will reproduce the noise and can be "felt" with a hand on it (bit no crack in the spring is obvious unless it's down in the spring cup), and the noise can be "felt", again with a hand touching) at the inner end of the lower control arm at the bushing. I loosened the inner bushing through-bold and lubed it and left it loose (so the entire bushing could ratate rather than twisting as it's designed to do), and there was no change in noise/feel, so I don't think that's the cause. I think that end just resonates. Nothing felt at the outer end of the control arm at that bushing, or anywhere else, so I am thinking maybe the spring is broken where it cannot be seen down in the cup (I wouldn't think that part would be stressed enough to break it, but...).

Next step is lower the control arm and pull the spring and look at it, which will also isolate the shock for checking, but I seriously don't think it's the shock.

Levering the spring with the suspension hanging causes the noise while NOTHING else in the suspension moves, which rules out most of the joints I'd think.

cgshawaii

Bob, you're well on your way.

I'll note that the creak is probably caused by two parts rubbing together, so by lubricating various joints you're approaching this correctly.

An old trick is to put your thumb over the blunt end of a stout screwdriver, with the blade held firmly against various components which are then moved slightly, to try and zero in on the source of the noise. A simple mechanic's stethoscope, if you will.

bobinyelm

Yes, Did this and the ONLY two places the noise could be sensed/heard was on the spring itself, and at the inner bushing of the lower control arm (that bushing was eliminated by loosening the thru-boit and oiling it, so I suspect it IS the spring which after all SITS in the lower control arm).

I just need to drop the control are, remove the spring and examine it.

Bob

efzauner

look at the base of the spring. This is where it breaks... a 3-4 inch section. It may be hard to see unless you can look into the base of the spring.

bobinyelm

I did my best to look to see this but can't.

But I am convinced enough to just pull it and probably replace both with new Bilstein springs rated for the wagon regardless.

Thanks,
Bob

slammer111

Only 1 way to find out. That creak must've been annoying. Hopefully this fixes the problem. Good luck.

bobinyelm

X10

It went from utterly silent to ear splittingly noisey in one day, so I have no doubt SOMETHING broke.

Wear generated noise tends to start gradually.

Got the flu right now, but I'll report what I find when I get at it..