If a valve seat insert, similar to that shown in the illustration is cracked, this may be indicated by __________. Illustration MO-0043

Correct Answer: Option A — white vapor in the exhaust gas

A cracked valve seat insert or cylinder head allows cooling water from the jacket to leak into the combustion space during the intake or exhaust strokes. The intense heat instantly vaporizes this moisture, resulting in distinct white vapor exiting through the exhaust stream.