Timing chains were much more common than timing belts. While this balance has shifted, manufacturers still use timing chains in modern engines. Over time, the chain will wear down and the links will become looser. Its called "stretching" but it really does not stretch, per say. This can cause the engine to be out of time and therefore not run efficiently. The worst case scenarios is that the chain will jump a tooth or potentially break causes severe engine damage The causes is poor maintenance (not changing your oil regularly) and mileage. Avoid the catastrophic click here to book a service today and we will send a mobile mechanics to service your vehicle at home or work. Or call Hometune Mobile Mechanics 096303000 to find out if your vehicle has a timing chain or cambelt.