What is the sign of a burned out engine?

Answer 1

Depends what you mean by "burned out." A "blown" engine is an engine with severe internal mechanical failure. It could be anything from a broken connecting rod to a cracked engine block. Such engines usually will not run at all. If the do run, they make horrible metallic noises and shake a lot. The most common major failure is a broken rod cap. This is presaged by a rythmic hammer-like banging that increases with engine speed. A plain worn out engine usually shows itself by generating clouds of greasy smoke, as the lube oil leaks past the piston rings and/or the valve seals.