Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Positive Crankcase Ventilation (PCV) System
Overview
The PCV system circulates crankcase gases through the intake air system into the engine where they are burned. The PCV system regulates the amount of ventilated air and blowby gases to the intake manifold.
The PCV system on some vehicles will be equipped with a removable PCV valve, a PCV valve integral to the valve cover, or a crankcase ventilation oil separator, as part of the PCV system. The PCV system on some vehicles will include a crankcase pressure sensor to detect a disconnection of the fresh air hose!.
The PCV systems comply with on board diagnostics (OBD) PCV monitoring requirements to prevent accidental disconnection from the valve cover. For more information about the PCV monitor and crankcase pressure sensor, refer to Positive Crankcase Ventilation (PCV) System Monitor.
Typical PCV System For V-Engine
Typical Quarter Turn Cam Lock Design PCV
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.