In this brief article we are going to discuss the suspension issues that occur in the BMW Z4, what causes these failures and some troubleshooting tips.
The Top 5 Most Common problems with BMW Z4 Suspension are:
- Rear Shock Absorber Failure
- Rear Squeaking Noise
- Steering wheel shake at low RPM
- Knock Sound while Steering
- Front ‘Clunk’ Noise
BMW Z4 Suspension
The BMW Z4 is the third model in succession within the BMW Z Series. The Z4 is the successor to the outgoing Z3 and is based on the E85/E86 platform.
The Z4 front suspension is carried over from the E30 3-series models. It is a MacPherson Strut suspension with an Anti-Roll Bar.
The “Z-link” rear suspension is common with the E46 (3 series) cars. This arrangement has a large semi-trailing arm, an upper link and a lower link per side.
Troubleshooting problems with BMW Z4 Suspension
Rear Shock absorber Failure
- Poor handling especially during slightly fast cornering
- Rear end feels less stable
- Knocking and Squeaking noises
- Bouncy rear end going over bumps
- Rear wheels feel ‘floaty’ going over rough patches
Troubleshooting Rear Shock absorber Failure
- Handling problems usually point to a problem in lateral grip. Now this could be either the tires or the Rear Shocks.
- It seems that the inside wheel was not planted enough on the tarmac to get lateral grip.
- Going over rough surfaces, the damper’s job is to keep the tires planted on the road surface. The ‘Floaty’ feeling is clearly due to a lack of Damping at the outside corner while cornering.
- Squeaks and Knocks are also typical symptoms of Shock Absorber failure
- Once the Tire is ruled out as a potential cause, then the only remaining Root Cause is the Rear Shock absorber. Weak/Leaking Shock Absorbers can cause lateral grip problems.
- Check the condition of the shock absorbers’ upper and lower mounts
- Also check for oil leakage stains on the shock tube
- Even if there are no oil stains, the shock could have simply worn out over the miles. Typically the shocks would last around 40K miles depending on usage. It is recommended to replace at 50K miles, when you would most likely see deterioration in performance
- While replacing the shock, make sure to replace the rubber mounts and bump stops as well.
Rear Squeaking Noise
- The Rear squeaking happens when going slowly and climbing a carpark ramp
- Otherwise no noise issue while going over bumps
Troubleshooting Rear Squeaking Noise
- In order to identify where exactly the squeak is coming from, you can simulate the rear suspension movement and closely observe the squeak closely
- For this, lift your rear body and place it on Jack-stands
- Now use a hydraulic jack to lift and lower the rear wheel hub to simulate suspension movement
- Move the rear wheel carrier up and down a few times and listen closely for the source of the squeak noise.
- If needed, you can use a long shaft Screwdriver and place the handle at your ear while the tip is at various suspension mounting points.
- Lower Control arms are known to squeak from past experience
- If the bushing is still intact and in working condition, you can try a “Quick-Fix” solution to eliminate the noise problem
- Use a Pointed tool to poke holes into the exposed Rubber Portion of the Bush
- Spray WD 40 into the new bushing holes using a nozzle
- Once again, using the Hydraulic Jack, move the rear wheel carrier up and down in order to let the lubricant spread throughout the joint.
- Lower the vehicle and see if the problem has been eliminated in normal driving
Steering wheel shake at low RPM
- The steering wheel starts to shake at low RPM / engine loads.
- Tire Balancing verified to be OK
Troubleshooting Steering wheel shake at low RPM
- The first item to suspect would be the Control Arm bushings
- From experience, these do wear out and cause minor stability issues
- To avoid risk, BMW front control arms are frequently replaced when the bushings wear out, as they are press-fit.
- If, for some reason, during the press-fit process, the control arms get bent or distorted, it could result in a variety of problems related to the steering and front suspension.
Knock Sound while Steering
- When the car is at standstill or very slow speed, ‘Knocking’ or ‘Creaking’ sound every time the steering wheel is turned
- More noise when locking the steering
Troubleshooting Knock Sound while Steering
- Jack the vehicle and remove both front tires
- Have someone move the steering wheel back and forth while you listen carefully to the sounds that the front suspension is making
- For MacPherson type of Front suspension, Strut Top mounts are known to become noisy when they fail.
- Damaged Top mounts do not allow the strut to rotate when turning the steering wheel. This creates the ‘Knock’ or ‘Creak’ sound
Front ‘Clunk’ Noise
- Almost a continuous noise during normal driving
- The Noise gets really worse on a rough patch
Troubleshooting Front ‘Clunk’ Noise
- Front Clunk noises on a Rough patch is most indicative of Anti-Roll bar (ARB) linkage related issue
- Apart from cornering, the ARB’s work a lot while driving on a rough road since the wheels articulate in a roll motion
- Inspect the ARB assembly and check all linkages
- The first linkage to fail within the ARB assembly is the Drop Links
- The Rubber boot covering the ball-joint usually ruptures due to ageing and the ball-joint inside loses lubrication and eventually rusts or seizes
In this brief article we have discussed the suspension issues that occur in the BMW Z4, what causes these failures and some troubleshooting tips.