Hi there, A leak down test will show the condition of the compression rings but not the efficiency of the oil control ring, and it wont show faulty valve stem seals, rule of thumb is, if it smokes when first started then clears up this is normally valve stem seals, oil burning under power or over run, that is high road speed then back off the throttle is usually rings as there is not the volume of oil passing through the stem seals to show up for very long. When the engine sits hot, the thin oil can run past the worn stem seals and sit on the valve this builds up for a time till the oil thickens up and this oil is burnt in a puff of smoke on start up.
Mark (mhpautos)
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Monday, October 26th, 2009 AT 6:43 PM