What is the difference between a timing belt and a drive belt?

A car engine showing the drive belt and pulleys

Drive belts are also known as “serpentine” belts, after the serpentine route they follow around several pulleys. In practice though, this image shows the single biggest difference between drive belts and timing belts.

The best way to appreciate the differences between timing belts and drive belts is to think of the following-

  • Drive belts do not have teeth as timing belts do
  • Drive belts drive the alternator, A/C compressor, hydraulic power steering pump, and on some engines, the water pump also. Timing belts do not drive these components, except the water pump on some engines
  • Drive belts are always clearly visible at the front of the engine, while timing belts, on the other hand, are never visible because they are protected by covers
  • When a drive belt breaks or fails, the engine will continue to run, while when a timing belt breaks, the engine will always cut out immediately
  • All engines will always start if their drive belts are not fitted. However, no engine can start and run without a timing belt, because a timing belt regulates the opening and closing of the engine valves
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