When a timing belt breaks while the engine is running or during ignition, the pistons can continue to move while the valves are still open, causing the valves to come into contact with the pistons. This contact can bend the valves, preventing them from sealing properly and causing a loss of compression in the affected cylinder(s).
The likelihood of bent valves depends on several factors, including the engine design and operating conditions at the time of the belt failure. Some engines are more susceptible to valve damage from a timing belt failure than others, and higher engine speeds increase the risk of the valves contacting the pistons.
If the timing belt broke at a low engine speed or during cranking, there is a lower chance of the valves bending. However, if the engine was running at higher RPMs or under load, the risk of bent valves is higher.
To determine whether the valves are bent, a compression test can be performed on the engine. If the compression is low in one or more cylinders, it could be an indication of bent valves. Additionally, a visual inspection of the valvetrain may be necessary to confirm the condition of the valves.
