ASE A4 Suspension and SteeringSteering System Diagnosis and RepairHard
A vehicle with hydraulic power assist experiences a persistent, high-pitched whining noise that increases in pitch with engine RPM. The steering effort feels normal. Upon inspection, the power steering fluid in the reservoir appears foamy and discolored. What is the MOST likely cause of these symptoms?
- AA worn power steering pump bearing.
- BA faulty power steering pressure relief valve.
- CAir ingestion into the power steering system.
- DA restricted power steering return hose.
Show answer & explanationAnswer & explanation
Correct answer: C. Air ingestion into the power steering system.
A high-pitched whining noise that increases with engine RPM, combined with foamy and discolored power steering fluid, is a classic indication of air ingestion into the power steering system. Air in the fluid causes cavitation in the pump, leading to noise, foaming, and accelerated fluid degradation.
Why the other options are wrong
- A. A worn power steering pump bearing would cause a whining noise that increases with RPM, but typically without foamy fluid, and often accompanied by increased steering effort if the pump is failing.
- B. A faulty power steering pressure relief valve would primarily affect steering effort (either too high or too low) and potentially cause pump noise under high load, but not typically foamy fluid from air ingestion.
- D. A restricted power steering return hose would cause increased pressure in the system, potentially leading to hard steering, fluid overheating, and leaks, but not typically foamy fluid or a high-pitched whine from air ingestion.
Power Steering Air Ingestion
Air ingestion into the power steering system causes a high-pitched whining noise (cavitation) and foamy, discolored fluid.
- High-pitched whine with RPM.
- Foamy, discolored fluid.
- Caused by leaks on the suction side.
- Leads to pump damage.
Memory trick: Whine and foam? Air in the system, bring it home!