Valve stem seal problems are as old as overhead valves. Those puffy brown rock-hard deposits (that can
look kind of like brown ice cream) on the spark plugs aren’t always so noticeable on some engine platforms with
leaking stem seals, but they blatantly tell the tale on others. Visible symptoms range from a puff of oil smoke
from the tailpipe when starting the engine after a soak to a full blown bug-truck mist that hangs in the air for
minutes after a vehicle passes. Some engines seem to give more valve stem seal trouble than others.