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.
PCV System: Operation
On gasoline models, during idle and low speed operation, high intake manifold vacuum pulls blow-by gases into combustion chambers for burning. During wide open throttle operation, low intake manifold vacuum and high blow-by gas pressure forces some crankcase gas through a hose to air cleaner.
On 760 GLE Turbo Diesel models, the oil separator valve regulates crankcase vacuum. The valve is normally open allowing gases to flow out of crankcase and into turbo air inlet. When turbo inlet vacuum exceeds a pre-set value, oil separator valve closes preventing oil from being drawn into turbo intake as well as preventing excessive crankcase vacuum.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.