Rear knocking sound

[Guest iactac]

I've noticed a knocking / juddering noise when pulling off in my W204 recently. It seems to be coming from a rear wheel (right side). You have to off your radio to be able to listen to it or get someone to sit behind.

The sound is more distinct when when pulling off and at low speed. It all disappears when you speed up (eg driving in expressway). Of course, I removed all the items in my boot yesterday night and drived up and down the street - the noise is there.

Anyone have the same problem and how to get this resolved. I hope it is not something more serious with the suspension/bearing....btw, my W204 is only 9 months old.....

[Guest johnphua]

iactac wrote:

I've noticed a knocking / juddering noise when pulling off in my W204 recently. It seems to be coming from a rear wheel (right side). You have to off your radio to be able to listen to it or get someone to sit behind.

The sound is more distinct when when pulling off and at low speed. It all disappears when you speed up (eg driving in expressway). Of course, I removed all the items in my boot yesterday night and drived up and down the street - the noise is there.

Anyone have the same problem and how to get this resolved. I hope it is not something more serious with the suspension/bearing....btw, my W204 is only 9 months old.....

I had this problem before when my w204 6 month old. I also removed everything from my boot and apply oil to all the joints but unable to solve. I brought my car to mbm and the Ah yong really good and managed to identify the cause...... it was caused by the rear windsceen. He spray some oil to the joint at the rear windscreen and the sound gone until now my car already 17 months.

[Guest iactac]

Thanks....hard to think the problem is due to windscreen as the noise came from the boot....It sounded that something is loose and kept rolling up and down in the boot (or the chassis).

My W204 is from C&C; so not sure whether the folks there are able to identify the issue. If it is not something I should worry about, I can live with it as the noise really is noticeable at low speed and when the car is very quite. Anyhow, will call C&C later.

[Guest Terence333]

I had this strange noise problem also when my w204 was new.The sound seemed to come from the back, during service they tightened all joints at the undercarriage but still got noise.Later with another experienced service advisor, he explained that it's the purge valve & canister problem at the front engine compartment;they added some rubber padding, it's now resolved.

[Guest JGoh]

Sounds like different rears get knocked differently???

(sorry, couldn't resist...)

[Guest iactac]

Well, did not call C&C as I guessed they will tell you to send the car down for inspection....not free until end of dec; so dont bother to call now (unless the noise persists and getting worst).

Anyhow, I tried to relate the problem is due to the rear windscreen as described by Johnphua. So, I tried to wind up and down the windscreen a few times, clicked the window button a few times to ensure it is fully secured. Interestingly, the noise kind of disappeared by itself for a while. When it came back, it was not that loud and I tried the same method, it disappeared again. Don't know what is really wrong and will continue to monitor. In anycase, thanks to you John - at least it has kind of remove the unpleasant noise I am experiencing to-date....

One thing I noticed is the noise is not present when you are driving at high speed. I have tried that for 2 days. I off the radio while driving at high speed (above 60/80/100) - conclusion: No knocking sound!!