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.
Crankcase ventilation
The air intake system has a vacuum during vacuum motor operation. This will cause the volume control valve to open and the cleaned blow-by gases to reach the intake ports and thereby the intake system through bore holes in the cylinder head. Since there is a risk that oil is suctioned through the crankcase ventilation in the event of high vacuum pressure, the volume control valve has a throttle function. The volume control valve limits the through-flow and thereby the pressure level in the crankcase. The vacuum in the crankcase ventilation keeps the non-return valve closed. Additionally, fresh air flows into the oil separator through a leak bore hole located above it. This limits the vacuum in the crankcase ventilation to a maximum of 100 mbar. During charged operation, the pressure in the air intake system will rise and thereby close the volume control valve. In this operating condition, there is a vacuum in the clean air pipe. When the non-return valve opens to the clean air pipe, the cleaned blow-by gases will be routed to the air intake system.
The following illustration shows the installation position of the crankcase ventilation.
| Index | Explanation |
|---|---|
| 1 | Oil separator |
| 2 | Non-return valve to the fresh air pipe with leakage bore hole |
| 3 | Pipe to the clean air pipe |
| 4 | Deflector with upstream fleece |
| 5 | Fine separator plate with small air vents |
| 6 | Pre-separator |
| 7 | Blow-by gas input |
| 8 | Oil return |
| 9 | Oil return with non-return valve |
| 10 | Connecting line to intake port |
| 11 | Volume control valve to the air intake system with throttle function |
NO RELATED
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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.