Hi everyone,

So - I've had my 1984 300D for about a month now, and since buying it I have noticed a weird, somewhat-unpredictable noise. The noise sounds like a sort of metallic "clunk" but more akin to the kind of "reverberating" "boingggggg" noise you might hear if you hit a large spring with a hammer.

I've heard the noise under the following conditions:

1) Hitting a speed bump a little too fast
2) Going over a speed bump while cornering (again a bit too fast)
3) If the car's weight shifts quickly while cornering
4) Hitting cracks or other obviously small, sudden bumps in the road.

Maybe more importantly, these are the only sorts of circumstances under which I've heard the noise. The car certainly feels like it handles normally - it doesn't pull or make other strange noises.

Actually - it does make one other noise I cannot pinpoint and that is, if I'm on the freeway, I begin to notice an odd, thrumming sort of low hum. The hum is periodic, and the intensity of the hum increases and diminishes over the course of about a second. Like a sort of "whooom....whooom...whoom". I only ever hear this if I'm going over about 90km/h, and It starts to become really apparent to me if I am over about 110km/h. I am not sure this is related to my first noise, but it might not hurt to ask. The noise is a pretty "low-frequency" sounds, so it is difficult for me to tell where it originates. So far, I know I hear it with the tranny in D, and also with the tranny in N (no change in the noise at all between those two)

Anyway, I am thinking maybe the first place for me to start is to check the shock mount, and maybe the bushings. Anything else I should be considering?

Thanks in advance!

holy cow... very weird noise (spring hit by hammer)

I think your car has the plastic sway bar links in the rear that are notorious for breaking and causing a lot of sounds going over bumps. but the spring sound....that sounds like it maybe something else. A loud unpredictible clunking (rythmic to the tire speed) in my case was the CV axle, or half shaft.

Is it coming from the rear?

And have you done a visual inspection of the bottom of your car, like looking at the exhaust and hangers, the flex disc at the rear, the CV boots, etc.

I had a sound that was over bumps that turned out to be the vaccuum pod (egg carton looking thing) in the trunk was loose.

I would recommned first doing a complete visual to see if something jumps out.

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85 300CD Turbo "Das Polluter" 230K sold for $3,000

98 BMW 323is

Hi Spugeddy - thanks for the reply.

Well - my characterization of the sounds might not be the best (or most accurate) description. That's just what it sounds like to my ear. It really is predominantly a "clunk" sound. The clunk sound is certainly _not_ related to the tire speed though, that I can say with certainty.

I plan to get under and do a really thorough visual, but first I need to get some tire with a friend's ramps and creeper.

It is coming from the rear though (I am 99% sure the driver's side rear, too).

I'd like to say I can do a visual and report back soon, but this time of year with the holidays coming up and then the wife and I planning to be out of town, I probably won't get a chance to look at it until the new year. The swaybar links though, hmmm. I will be sure to look at those first!

+1 to swaybar links...check em out first

I forgot to reconnect one of mine after a job and it made similar sounds. Very scary ones at that...

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Yeah, these
https://www.***************/search/product.aspx?sid=ly0s32fzlszx4mv4302q5z55&makeid=800016@Mercedes&modelid=1193576@300CDT%20&year=1984&cid=27@Suspension%20System&gid=7580@Stabilizer/Sway%20Bar%20Link

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83 SD

84 CD

I too would first look at the swaybar links. But those usually make rattling noises. I reaplaced mine and it quieted the rattleing noises, but now I too have a loud boing noise every so often. It's usually when I make a hard turn into a steep driveway, or when the there is lots of uneven ground, going slow around a corner. Keep us posted on what you find.

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Well it sounds like you can rule out the cv axles, flex disc, etc...

If you have a broken sway bar link, it may be clanging around since it would be loose.

That would be a very easy cheap fix....if you are lucky enough.

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85 300CD Turbo "Das Polluter" 230K sold for $3,000

98 BMW 323is

I had a similar sound when I first bought the SD, freaked me out but it was only the exhaust hangers, 2 were gone and the other 2 were about to go.

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1985 300SD