Mechanical Diagnostics
BMW ECS Rear Shock Mounts
Client reporting abnormal (thudding) type noise when going over bumps at either low speed or high speed after the installation of a performance sway bar at another shop. Client has had some work done with this shop previously on the following:
- Performance Coilovers
- Performance sway bar
- Complete Bushing Refresh
- Full Performance Brake Job
- Complete Engine Seal / Coolant Hoses Refresh
- Super Sprint Headers & Exhaust System
Overview
The sound initially started in the rear driver side area and has since progressively gotten worse, the client has since taken his car to the initial shop that had the work done to his car multiple times with no luck as to what could be causing that noise. The last visit yielded to the mechanic informing the client that they think the noise could be caused from the sway bar bushing and that they have tightened the sway bar linkage bushings a bit more & that seems to have solved the issue.
Over tightening this bolt actually caused the bushing to compress so much that it prematurely destroyed it.
Since then the client was still facing the same issue with the thud / sound while driving over uneven road surfaces or through speed bumps.
Testing
When we received the vehicle from the client we noted down what work has been done to it recently so that we can narrow down what the cause can be.
We then took it for a through test drive to experience the sound the client is experiencing first hand.
right off the bat, we noticed the loud thud noise when going over the smallest uneven road surfaces and larger thud noises when going over speed bumps. the test drive did not last long before we could head back to inspect the vehicle.
We first inspected for any loose items in the trunk that could be the cause of the issue, as the noise seemed to be prevalent a bit higher up in the car. This led us to finding out the battery was loose even when strapped in (most probably different size battery than original) we used a spacer in between the battery strap and battery to nudge it in (to make sure this was not the cause).
We then checked under the car for any worn bushings that could be the cause of the sound, only to find that most of the bushings have already been replaced except for the lower rear trailing arm bushing, but this could not have been making that noise.
So we then moved onto the suspension bushings, the lower one was new as the client has just installed some KW coilovers, and the upper shock mount was the ECS branded shock mount. We first checked for any side to side movement, but there was none at all. We then checked for any vertical movement and found out that sure enough, lifting the tire while the car was lifted from the ground, led to some slight upward and downward movement in the inner part of the upper shock mount that was not normal at all.
Diagnostics
Next step was to remove the upper shock mount and inspect what could be causing the vertical movement of the mount itself. everything seemed to be torqued to spec, but once removed and inspected the inner monoball seemed to freely move upward and downward by hand.
After disassembling the mount itself and inspecting the innard of the mount, it turns out that the 80A polyurethane isolation bushing has abnormally degraded, to the point where it would break apart when running your fingers through it.
The client has only had this on his car for the last 10,000KM, so this wear on the bushing is most probably a manufacturing defect.
Conclusion
To solve the present issue for the client, We went ahead and installed some stock upper shock mounts to replace the defective ECS Mounts with as a temporary solution, ECS was quick to respond to us with an option to either replace or refund the order amount for the warranty claim.
The Client has request that he is looking at getting a different brand performance upper shock mount over the ECS one for the warranty claim.