Will engine damage occur when timing belt breaks on 1999 mercury mystique ls sport 2.0 motor non interferance engine?

No, engine damage will not occur if the timing belt breaks on a 1999 Mercury Mystique LS Sport with a 2.0-liter non-interference engine. In non-interference engines, the design allows for the pistons and valves to not collide even if the timing belt fails. As a result, the engine will simply stop running, but the internal components should remain unharmed. However, it's still important to replace the timing belt at recommended intervals to prevent unexpected breakdowns.