DrDoe

04 S430 Airmatic with knocking sounds. The sound is heavy knocking when running over bumps and it comes from the front driver side.
Lemforder Ball joints, Spring control arms, Upper control arms, Lower control arms, Sway bars were replaced but the sounds are the same before and after the changes.
Couple shops spend 1/2 hrs looking at it and both have no ideas. Could the struts caused the heavy knocking sounds? And how to test? Is there something in Xentry that can test the struts? Car raised and lowered perfectly and level correctly.

turbonos7

Have you checked and made sure that the two set screws at the bottom of the strut are tight against the strut seat? If they're loose, that can make a clunking sound when going over bumps.

wallyp

I had a rear strut that did exactly that - internal failure, worked fine, but knocked heavily on every bump.

DrDoe

Yes if you are talking about the ones that's connected to the springs control arms...

DrDoe

Is there anyway to test? Or just go ahead and replace?

wallyp

In my case, the diagnosis was unfortunately easy - the original strut failed, so I installed a new Arnott rebuilt. It knocked. Arnott sent me another one - it didn't knock.

I know of no way to diagnose the problem...

DrDoe

I went ahead and ordered the struts with this info. Thanks!

DrDoe

Well, I ordered driver front strut through AutoZone yesterday and got it today before 10AM. Installed it but unfortunately the sound is still the same. It's coming from the driver front and heavy knocking sound when running over bumps.
What are the chances the replacement strut have the same problem as the original strut?
This car is 135k miles on original strut so I don't mind to have a spare strut but I'm at a loss on how to get rid of the knocking sound.
The only other thing is to install the original driver front strut on passenger side to see if knocking come from both sides.
Any other ideas?

AlexMercedes

It could be the top mounts. I know the abc struts have the top mount issue which cause a similar issue but I'm not sure about airmatic.

DrDoe

Here's the top of airmatic strut. The 3 nuts and bolts connected the strut to the car. Nothing else between the strut and the car. Air connected to the brass fittings in the center. .

DrDoe

Update: I went to an MB specialist shop for diagnostic on the knocks. The guy spent an hour on it and couldn't find the causes so he had me bring it back for more time overnight. His diagnostic: Bad strut in the internal.
I went back to AutoZone and exchanged for another Arnott strut. Installed the 2nd Arnott strut and the knocking is still there.
Returned the $400 Arnott strut to Amazon and just ordered a $125 maXpeedingRODS from Amazon for one more try...

tyl3r

Hi
I had the same problem - almost imposible to find. Turned out the tranverse control arm required replacing, The gaiter where the strut mounts was split (bottom) allowing water to corrode the joint. Its worth a look.
Good luck - tyl3r

DrDoe

Those arms were bad but no changes to the heavy knocking sound after the replacement. I was hoping those control arms were the culprits.

GunDriver

Not sure how the brakes are made on your car but this quote from a w204 thread may help
" Rattle
After completing a a total suspension rebuild and brake replacement on a 2009 c300 I experienced the same rattle you describe. Rattle during low speed bumps, only when accelerating? No rattle when braking?
If so, considering the work you had done, my bet is the mechanic did not install the anti rattle clips on the front calipers when putting the brakes back on. I couldn't figure out for 2 weeks what was causing the rattle. No YouTube videos or forums mentioned the clips, but I figured since they were included in the brake kit they must go somewhere so I was finally able to figure out how they fit. Rattle was gone"

DrDoe

My knocking issue had been resolved. The dealer figured it out finally. It was the wheel hub. So the air struts on this car are still original since 2005 and 135000k miles.