There are two ways to tell if the timing belt has been replaced. One is obvious-you are looking at a service receipt showing the replacement.
Swimlane diagrams are used whenever you need to show activities, tasks, or process steps which are being performed by different actors/roles. You can use swimlanes to group activities in an activity diagram or process flow by any category what you need: by role, by system, by department, etc.
How to create a swim lane diagram or a cross functional flowchart in Visio 2010. This video covers swim lane creation and modification, shapes and connector types, and multiple page tips.