shock noise??
 

I recently had my front shocks replaced at a local repair shop - not at a MB dealer.

Ever since the shock replacement (with a generic brand), however, the car makes a thump noise from the right front side every time I go over a bump driving at 20 - 40 mph. Any speed below 20+/- or over 40 +/- does not produce the noise. The left side does not make any noise. I went back to the mechanic, who upon detailed inspection, found nothing wrong.

Any leads?

Maybe double check the nuts/ bolts for tightness on that side ?
Normally it is best to tighten the bottom nuts/bolts with the car resting on the ground, rather than on a hoist.;)

Model?

Thanks for the replies. It's 420 SEL that's making the noise.

The mechanic rechecked all the nuts & bolts but still the noise is there. BTW, the mechanic assured me that it's not a safety issue. However, when I go over several consecutive cracks/bumps on the road, the noise bothers me a bit.

Could this thumping noise be related to a rope tightening noise when I turn the wheel while in park?

I appreciate any suggestions.

I suspect your car is put together much the same as mine, and I would have a look at your swaybar and outer bushings. Frequently the swaybar itself wears in the area that constantly slides inside the outer bushing. On smaller bumps at that speed, the bushing play will cause a prominent knocking as the sway bar moves up and down with the suspension. All this assumes you've already ruled out the usual suspects (tie rod ends, ball joints).

I would second the above info. I don't know about your W126 chassis, but on the W124s like mine, front swaybar bushings generally last about 75 k miles. Mine made a "thunk" sound over bumps, esp. with the wheel turned slightly.

Cheap and easy fix.

My dealer misdiagnosed the noise as blown shock tower mounts and estimated $1200 to fix. Instead I learned about the swaybar bushing problem and spend $50. Problem solved.

Thanks benzfan and 400E. I will look into this this weekend.

FWIW, On mine, new bushings would not help as the bar was worn too much. I got some heat shrink tubing (the really heavy, stiff stuff with hot melt glue inside - Canadian Tire item where I'm from). I 'shimmed' the bar with it as a temporary fix some months ago and made sure to use synthetic grease when putting the bushings back on. That was 25,000 km ago. If and when it wears, I plan to do the same thing again until I get up the motivation to put some Eibach bars on. It's still rock solid as a 'temporary' fix.

frontosa:

My 126 does something that sounds like what you're describing.

The thunking/clunking sound sounds like something in the front left suspension is LOOSE. It only occurs when going over a *sharp* type bump, ie, railroad tracks or a bumpy/rocky road....something other than a smooth transition bump like a driveway curb or a smooth speedbump.

Everything has been checked up front except the sway bar bushings. This may be my problem as well.