ASE A4 Suspension and SteeringSuspension System Diagnosis and RepairEasy
A technician is diagnosing a vehicle with a multi-link rear suspension that exhibits a noticeable 'squeak' when going over speed bumps or when the rear of the vehicle is loaded. The noise is intermittent and seems to come from the lower part of the suspension. A visual inspection reveals no torn boots or obvious damage, but some of the rubber bushings on the lower control arms appear dry and slightly cracked. Which of the following is the MOST appropriate initial diagnostic step?
- AReplace all rear lower control arm bushings immediately.
- BPerform a complete four-wheel alignment.
- CSpray a silicone-based lubricant on the suspected bushings and re-test.
- DDisassemble the suspension to inspect internal components.
Show answer & explanationAnswer & explanation
Correct answer: C. Spray a silicone-based lubricant on the suspected bushings and re-test.
Spraying a silicone-based lubricant on dry rubber bushings is a quick and effective way to temporarily eliminate squeaking noises, confirming the bushings as the source before recommending replacement.
Why the other options are wrong
- A. Replacing all bushings without confirming the exact source is premature and potentially costly if the noise persists.
- B. A four-wheel alignment addresses geometry, not usually squeaking noises, unless related to extreme component wear which would be visually obvious.
- D. Disassembling the suspension is an invasive and time-consuming step that should only be done after simpler diagnostic methods have been exhausted.
Bushing Squeak Diagnosis
Squeaking from suspension bushings often indicates dryness, hardening, or minor cracking of the rubber. Lubricating them can temporarily silence the noise, confirming the source.
- Common noise source on older vehicles.
- Silicone spray is a good diagnostic tool.
- Temporary fix; replacement is usually needed long-term.
- Prevents metal-on-metal contact and absorbs vibration.
Memory trick: Hear a squeak? Try to 'quiet' it to 'confirm' its source.