Crankcase pressure should be neutral at idle and negative above 1000rpm in a healthy engine. Pressure between the turbocharger and air filter is always negative and more than sufficient to scavenge normal blow-by from the crankcase.

A simple test is to remove oil filler cap and seal a thin piece of pollythene sheet over it with grease. At idle it should not blow off and as rpm is increased to about 2000rpm should suck into the cover slightly. If blow-by is sufficient to lift off a loose filler cap it's time for a rebuild!

A word of caution!Never block the breather with your finger (or anything else) while the engine is running. While this should cut the fuel in +/- 10 secs,if it fails to do so you will distort or even burst the valve cover.

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Beagle