In the case of a non-interference or “free-wheeling” engine, the worst thing that should happen, if the belt fails, is the engine will simply stop running. This certainly has other consequences, from a safety and convenience standpoint. In rare cases, a free-wheeler can also incur bent valves or damaged pistons, as carbon buildup can decrease clearances between the conflicting parts.
I don’t mean to spread fear, but this topic is an easy one to forget about when a car is perhaps seven or eight years old. If one is tempted to stretch the timing belt replacement interval, it would be wise to assess the risk that accompanies that decision.
Gates Corp. has a convenient look-up tool that indicates if an engine is of interference or free-wheeling design: http://bit.ly/PnCfzn. The tool could also be used to evaluate a future vehicle choice. If no “timing belt” or “cam drive” components are listed, it’s probably chain-driven. Deep breathing via chain is the best of both worlds.
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at firstname.lastname@example.org; he cannot make personal replies.