In the 2000 Toyota Sienna, the timing belt is a non-interference type, which means that the pistons and valves are designed not to contact each other even if the timing belt breaks. However, if the timing belt does break, it can still cause damage to the engine by disrupting the timing of the engine's ignition and fuel injection systems. This can cause the engine to run poorly or even stall.
In addition, if the timing belt breaks while the engine is running at high speed, it can cause the engine to overheat. This can lead to further damage to the engine, including warping of the cylinder head or even seizing of the engine.
Therefore, it is important to have the timing belt on your 2000 Toyota Sienna inspected and replaced at the recommended intervals. This will help to prevent the timing belt from breaking and causing damage to the engine.