I have a 1977 240D with 457, 900 miles on it. I am the original owner. I have replaced the front and rear springs; the front
(L & R) upper control arms (and ball joints) and lower ball joints.
The shocks are Bilstein (3 years old). Whenever I go over a speed bump or a road bump, I feel and hear a loud banging noise from the front suspension. I have had my mechanic check all underside parts for wear and loosenees. No luck ! Anyone got any ideas on how to get a "smoother" ride out of my 240D ??

My 74 240D had a mysterious knock in the front when I would hit a bump, or even turn into a parking lot. The problem was that the sub-frame mounts were fatigued. These are rubber shock mounts that cushion the suspension frame to the chassis and are easily overlooked. I suspect you are having the same problem.

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02 S500
92 500SL
92 400E (Sold)
87 300E (Sold)
83 300D Turbo (Sold)
75 300D (Sold)
74 240D (Sold after 20 years)

Will it make the noise if you push and pull un and down on the car by hand?
Maybe the strut is loose? They are pressurized and will try to extend with quite a bit of force so they will appear tight. If it is loose you will be able to see it by cycling the suspension up and down faster than the strut can move on it's own.

Hi Chevota,

No there is no noise when I push up and down on the body. The shocks seem to be working fine. Down one motion; up 1/2 motion .....Lovedabch

Well, I don't want you to hurt youself or your car, but when I'm looking for noises like that I usually have to get a little physical with the car. Since it only makes a noise on speed bumps etc, you'll probably need to be that hard on it. I usually push down with one hand and pull up on the fender well (or corner of bumper) with the other. To get an idea how hard; sometimes the car will bottom out on the down stroke and catch some air on the up stroke. An easier, but not usually very effective method would be to jack the car up and down slowly, listen for noise and watch for movement. Make sure the battery and radiator are secure, and it wouldn't hurt to check the motor mounts as well.

Thanks Chevota,

I'll look into your recommendation more closely (aggressively) ....Lovedabch

A couple of years ago I too had a pounding suspension noise. Like you, whenever I went over a speed bump or road bump I got a loud banging from the front suspension. When I also heard a grounding type sound when cornering fast, it was time to fix it.

So with 50K mi I replaced the first suspect, shot front shocks. Didn't fix it.

My front right wheel bearing had about 1/8 inch play so I replaced it. Didn't fix the pounding.

I replaced the ball joints and steering damper since they were worn. Didn't work but at this point the suspension is riding nice.

Finally, I found that the sound deadening material that lines the transmission shaft, on the underside of the car, was sagging and hitting the flex disc on the drive shaft. Since this sound deadening material goes up to the front fire wall and has parts made of metal, any sound seemed to come from the front of thr car and seemed worse than it really was. I ripped some of it out, near the flex disc at the transmission, and problem fixed.


On the line of Mercedes reliability/durability:
How is it that original Bilstein shocks can go out at 50K miles under nonabusive driving but the replacents have a lifetime warranty?

Good luck with your ills..........

PPatterson: Are you sure the original was Bilstein? I've never seen one wore out. I heard about a seal leaking on a shock once. If so, I'd like to hear exactly what wore out.

I always assumed Bilsteins were original equipment. There is no mention of this in the owners manual. The old and new shocks appeared to be the same when I replaced them. Perhaps this is one of MB's cost saving measures, use cheaper initial parts. There was no sign of damage on the old shocks, they just got soft.

Inspect the engine and tranny mounts good too.

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Jim

PPatterson:
Yup, I assumed all MB had Bilstein until I got this ML320 a month. I could feel the front topping out hard if I caught a little air, and I though there's no way a Bilstein w/ 70K could do that! I loooked and there is some off-brand twin-tube shock in there. Looks factory, but who knows.

I believe the clunk you describe is caused by front sway bar bushings rubber flattening out. - at least on the 123,126 style bodies they do.
Do a search - quite a bit has been written on this issue.

Hello Fellow Mercedes 240D & 300D Enthusiasts ! Well, I have replaced most of the front end parts and after all said and done; the most significan difference was noticed when I lowred the tire pressure from 35 psi to 29 psi. My ride have improved consideralbly. I may sacrifice some tire wear; but most of my driving in highway driving. Right now I am getting close to 33 MPG on my 300D (non-turbo) I appreciate all of your assistance and feed back. Safe benzing to you all !! Lovedabch in Virginia Beach, Virginia

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Lovedabch in Virginia Beach !!