Your relatively high level of blowby may mean that the pressure inside the valve cover is more than can be handled by the "PCV" system. The excess pressure is escaping any way it can, by going through the vent. Another possibility is that something is wrong with the vent system (hose collapsed or plugged up) and the blowby is escaping through the little vent. Better that than blowing a seal, I suppose.

Engines that don't have a vent in the side of the valve cover probably use a different type of oil breather. The vent hole is not hooked up to a tube because it's designed only to let the pressure regulator sense atmospheric pressure. In a new engine, the regulator keeps intake vacuum from pulling oil out of the crankcase. In an engine with very high blowby, all bets are off.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
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