Underneath the hole where the PCV valves go is a void, if you pull out the valve and shine a torch in you'll see what I mean. If you take off the rocker cover and turn it over you'll see 2 little hook shaped tubes (only about 2/3 mm diameter). These 2 tubes drain any oil that collects in the PCV void. Mine were both blocked on one side, so my PCV valve was sitting just above its own personal little pool of oil, sucking it into the inlet manifold every time I pressed the loud pedal. Went at it with a pice of strimmer wire, job done.

posted by polcon on the U.K. Board
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