Clunking noise in 300D - PeachParts Mercedes-Benz Forum

#1 08-18-2002, 04:05 AM

Hi All,

I have a clunking noise in my 300D. Judging by ear, the noise seems to originate from between the suspension area to just below the driver floorboard.

The noise generally comes up when I hit bumps in the road, turn left to right, or vice-versa while driving. The noise comes up EVERY time I shut off the ignition.

I have already brought the car to two independent MBZ shops and one suggested I replace the left ball joint which I did, but the clunking noise remained. The other mechanic could not figure out what causes the noise.

So, I decided to post this question to you all to get your feedback as to what is causing this annoying clunking noise.

Any and all help will be greatly appreciated.

Simon

The Warden · #2 08-18-2002, 04:59 AM

Cool, another Peninsula type.

You may take a look at the front sway bar. If the noise comes up every time you kill the engine, you may also want to take a look at the engine mounts and the tranny mounts.

Except for the noise appearing every time you kill the engine, it sounds a lot like a problem I had with a '65 Chevelle a while back; one of the bolts holding the front sway bar to the wheel suspension assembly had broken clean off. Combined with bad springs and bad shocks, the car handled horribly in turns...

Hope that helps a little. Good luck!

Ken300D · #3 08-18-2002, 09:30 AM

If it happens every time you cut the motor off, that helps you in finding the problem if you can get outside the car and have someone else turn the engine off. There are a lot of rubber bushings in the front suspension of these cars - control arms, etc. Hopefully you can first determine which side it is on, and then start shaking things by hand and doing a visual inspection.

With regard to motor/transmission mounts, there are two rubber blocks on each side of the engine, and one rubber block at the back of the transmission. If you're leaking motor oil or transmission fluid it shortens the life of these rubber blocks.

I don't think a bad ball joint will creak/croak when you turn off the engine. Open the hood and watch/listen on each side of the engine. Also consider that a broken air cleaner mount will let the cleaner housing bump against things and make some unbelievably loud noises.

This is something you can find with time invested to track it down - better than a mechanic that spends five minutes and then starts advising you on things that "need" replacing.

Ken300D

MVK · #4 08-18-2002, 09:58 AM

Check the engine mounts and engine shock. Also check for any other metal pipes that might have come loose off of its clamps. eg. AC compressor lines etc. Check the mounting bolts on each of the external componenets like steering pump, compressor, alternator etc. just to make sure nothing is loose and ratttling.

Cluncking upon acceleration, or shutting off engine is typical of a broken engine mount. Ceck the front sway bar and its bushings at the mounting point on the body.

While at it also rule out the broken air filter housing mount. Although this usually gives a terrible vibrating sound.

Good luck keep us informed as to what happens.

MVK

Palangi · #5 08-18-2002, 03:03 PM

I wouldn't be surprised if the air cleaner mounts are broken. (Cheap and easy fix) Worn engine mounts and engine shocks will shorten the life of the air cleaner mounts. In other words, you might have both problems.

#6 08-18-2002, 04:52 PM

Thanks to all who read/posted replies.

These are great suggestions as to the clunking noise. I forgot to mention in my original post that I have already changed both engine mounts a couple of times. Each time I changed the mounts, the clunking noise will disappear but over a short time come back again.

I was thinking maybe I should change the transmission mount as I am sure it is original and has never been changed.

A couple of you suggested the noise might be due to a broken air filter housing mount or the front sway bar. The housing mount is fine. I was thinking it could be the front sway bar. I'd like to check this out. Where is the front sway bar located?

Also, have any of you had this clunking noise happen when you shut off the ignition and what you did to fix the problem.

Thanks to all.

Have a pleasant day!

MVK · #7 08-18-2002, 08:26 PM

Hi Simon:
The front sway bar runs parallel to the fire wall connecting the upper control arm on each side.
Look for the upper control arm and in the middle of this upper control arm is the place where sway bars are connected. Trace it down futher towards the fire call and you will see the point of attachment for the sway bar to the body using a rubber mount. Check the condition of that rubber mount. Also move the sway bar using your hand it shoud not be loose.

MVK

RAYMOND485 · #8 11-14-2007, 12:43 PM

1984 300d Turbo 145k
One Of The Three Bolts On The FRONT Lower Rear Guide Rod 13 Mm Bolts Was Not Torque, Now Ok, No More Clunking Over Small Road Bumps Slow Speed Over Yellow Lane Markers

Thunderballs · #9 11-16-2007, 09:49 AM

Not to oversimplify, but my 85 300SD was acting as you described.
I found the exhahst system muffler hanger oring torn on the drivers side. Whe the Ex system was shaken sideways - no noise, when I lifted it vertically slightly it collides with the mount bracket and made the heavy sounding clunking. Takes 10 seconds to check.