The PCV valve is a component of the positive crankcase ventilation system. It is necessary so that the right amount of air enters the engine - for mixing with the combustion mixture, and the oil does not flow through the seals. Clear signs of a PCV valve malfunction are isolated oil droplets on the floor under the vehicle's underbody.

1. 3 (E46)
2. 3 Saloon (E46)
3. 3 Touring (E46)
4. 5 (E39)
5. 5 Saloon (E39)
6. 5 Touring (E39)
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The usage of the valve of VAICO brand Valve, engine block breather

The PCV valve consists of an external oblong body, in a section somewhat resembling a bullet, a PCV channel in its bottom, a valve, and a vacuum channel. The mechanism of operation consists in lifting the slide valve, which completely blocks the discharge channel.

If the ventilation system of the car does not work, this leads to less air in the engine, unreasonably increasing fuel consumption, oil leakage in the air filter, clogging of the throttle valve. As a result, all this can lead to the fact that overpressure is created gradually in the crankcase, which literally squeezes the oil out of the system, from all its possible outlets (increasing the oil consumption, creating pressure on the nodes).