Rear Suspension - Pops or Snaps on Dips and Bumps

GROUP 33
Rear Axle

Bulletin Number
33 02 99

Woodcliff Lake, NJ
April 1999
Product Engineering

SUBJECT:
Popping or Snapping Noise from Rear of Car

MODEL:
E46

Situation:
Some E46s produced prior to 7/98 may experience a complaint of a popping or snapping noise when driving over dips or hard cornering.

Cause:
When the rear suspension compresses the coil spring can stick to the rubber upper mount, and when the suspension extends the spring and mount separate rapidly, causing a popping noise that is amplified by the body.

Note:
It is possible to misdiagnose the cause of the noise as a loose fuel tank. The fuel tank can have as much as 5-7 mm of vertical movement at room temperature when it is not full. The tank will expand to remove this play when filled and the operating temperature is high.

Correction:
In case of customer complaint, the rear spring mounts can be coated with talcum powder, which will prevent the coil from sticking to the mount.

The mounts used in production beginning with 7/98 production have been coated to prevent sticking.

Procedure:
Raise the car on a lift so that the rear wheels hang free. Clean the upper coils and mounts of the rear springs with a dry shop rag. Do not use any spray cleaners or solvents on the mount.





Apply a liberal coating of talcum powder (baby powder) to the mount (1) and the spring in the contact area. Use a soft paintbrush to cover as much of the contact area as possible.

Any powder that falls on the lower mount can also be spread around the contact area with the brush.





Warranty Information:
Covered under the terms of the BMW New Car Limited Warranty.