Answer: If the timing belt fails, your entire engine will fail. If a timing belt is worn or stretched, it can throw off the timing of the valves and pistons. This can cause the pistons to hit a closed valve and damage or bend the valves and pistons. Again, if a timing belt is worn or stretched, it can disrupt the timing of your engine and cause serious damage to your engine’s valves and pistons, which will lead to a much more expensive repair.