Automotive Service Excellence (ASE) A8 Engine PerformanceEmissions Control Systems Diagnosis and RepairMedium
A technician is performing a pre-purchase inspection on a used vehicle. During the inspection, they notice that the Positive Crankcase Ventilation (PCV) valve rattles freely when shaken, and the hose connecting it to the intake manifold is soft and collapsing when the engine is running. Which of the following is the most appropriate action?
- AReplace both the PCV valve and the PCV hose
- BNo action is needed as the PCV valve rattling is normal
- CReplace the PCV valve only
- DReplace the PCV hose only
Show answer & explanationAnswer & explanation
Correct answer: A. Replace both the PCV valve and the PCV hose
A PCV valve that rattles freely when shaken is generally considered normal, indicating it's not stuck. However, a soft and collapsing PCV hose indicates it is deteriorated and likely has internal damage or is restricting flow, which can lead to improper crankcase ventilation. Both components should be replaced to ensure proper PCV system function and prevent future issues related to crankcase pressure or vacuum leaks.
Why the other options are wrong
- B. The PCV valve rattling is normal, but the collapsing hose is not. It indicates deterioration and requires replacement.
- C. While the PCV valve rattling is normal, the hose is faulty and needs replacement.
- D. The PCV hose is faulty and needs replacement, but it's good practice to replace the valve as well since it's a wear item and often replaced as a set with the hose.
PCV System Inspection
Checking components of the Positive Crankcase Ventilation system for proper operation and integrity.
- PCV valve should rattle when shaken (unless it's a fixed orifice type).
- PCV hoses should be firm and free of cracks, kinks, or collapse.
- A faulty PCV system can cause oil leaks, rough idle, or excessive oil consumption.
Memory trick: PCV: valve rattles, hose stays firm – if not, replace both!