When a timing belt breaks, the camshaft stops rotating, and the valves remain in their current position. As the crankshaft continues to rotate, the pistons move up and down, potentially hitting the open valves and causing them to bend or break. This can lead to a loss of compression, misfiring, and other serious engine problems.
In the case of the 1998 Hyundai Accent L 1.5 12-valve manual transmission, it is highly likely that some valves were damaged when the timing belt broke while driving at 65 mph. The extent of the damage will depend on several factors, such as the engine speed at the time of the failure and the exact timing of the belt failure.
It is important to note that operating a vehicle with a broken timing belt can cause catastrophic engine damage. If you suspect that the timing belt has broken or is damaged, it is crucial to stop the vehicle immediately and have it towed to a qualified mechanic for inspection and repairs.
