Pop sound: W123 - PeachParts Mercedes-Benz Forum

mbzkid · #1 08-14-2006, 01:15 AM

My 300D has developed a popping noise that usually occurs when coming to a stop and when accelerating from a stop. It can be felt through the floor board and slightly though the brake pedal, not the steering. The popping is worse when the car has been run for a long time, especially highway driving. This is one of the reasons that I suspect the wheel bearings. I can also hear a high pitched click, but very rarely. Its a sharp click which I can hear from the front right and sometimes near the drivers seat, which iss probably coming from the front left.

The popping sound would be equivilant to someone smacking the coil spring with a mallet.

When coming to a stop, the sound will start at appox. 15 MPH and pop 1-6 times as the car comes to a stop. As the car accelarates from that stop, and the suspension unloads, it will pop another three or so times. Other times, the pop will occur almost constantly when coming off the highway. It will pop/rumble as the car travels down a fairly smooth road, but only after a highway run. Eventually (as the car cools down?) the sound will only occur when braking/ accelarating.

I checked the left front bearing and as I tightened the bearing, I was unable to detect a difference in effort when turning the hub. The hub made a sort of rumbling noise as I turned it, yet when I drive the car, I am unable to hear any of the typical bearing noise that would be associated with a worn bearing. I don't hear any bearing noise as the car turns, or when weight is shifted to the front.

A shop that is known for doing front-end work, inspected the suspension and claimed the suspension was "tight." We were told it was the shock, and the shop has never seen anything like this before. I installed two new Bilstein shocks and the noise was gone for 15 or so miles. Then it slowly came back.

Needless to say, I'm a bit concerned about driving the car, and would like to hear your input.