Why would a broken timing belt hit a valve? What does a broken accessory belt do?
Nowadays, many cars use timing chains and generally do not need to be replaced, unless they become elongated and malfunction or make abnormal noises before considering replacement. Some cars also use timing belts, which are made of rubber. The belts will age after driving for many kilometers or over time, and if left unchanged, they will eventually break. Once the timing belt breaks, the harm is significant, which can damage the valves, pistons, and connecting rods, leading to the need for major engine
Nowadays, many cars use timing chains and generally do not need to be replaced, unless they become elongated and malfunction or make abnormal noises before considering replacement. Some cars also use timing belts, which are made of rubber. The belts will age after driving for many kilometers or over time, and if left unchanged, they will eventually break. Once the timing belt breaks, the harm is significant, which can damage the valves, pistons, and connecting rods, leading to the need for major engine repairs. Let's talk about why there is so much damage when the timing belt is broken? What will be damaged if the accessory belt, also made of rubber, breaks?
One end of the timing belt is connected to the crankshaft, and the other end is connected to the camshaft. The crankshaft is connected to the connecting rod and piston, and the camshaft controls the timing of valve opening and closing. That is to say, the movement of the piston and the opening and closing of the valve are interrelated. When the piston moves downwards during intake, the intake valve must be in the open position. When compressing, the piston moves upwards and all valves must be closed. The orderly and accurate coordination relies on the connection of the timing belt. This belt is a toothed belt that has an accurate position during installation, and almost one tooth cannot allow the engine to operate normally. Therefore, aligning the teeth when replacing the timing belt is the most difficult task and has a high technical content.
Because the space in the combustion chamber is very small, if the valve is not closed when the piston reaches the top dead center, the piston will push against the valve. Under what circumstances will the piston reach top dead center and the valve not close? The timing belt is broken or has incorrect teeth. The belt is broken, and both the crankshaft and camshaft are unconstrained, rotating freely without any coordination. When the timing of valve opening and closing is not correct, the piston reaches the top dead center and the valve just opens, pushing the two together. The valve will be bent, the top of the piston will be injured, and even the connecting rod will be bent.
Why not design it so that the valve opens, the piston reaches top dead center, and the two do not come into contact? If this is the case, the space in the combustion chamber is too large. To achieve the same compression ratio, the cylinder needs to be made very long, and the piston will waste more energy when running. The combustion chamber is too large, and in order to burn normally, the fuel injection rate needs to be increased, which can lead to poor fuel economy or power impact.
Next, let's talk about the accessory belt. What damage will it cause if it breaks? The power source of the accessory belt is the crankshaft, which is connected to the crankshaft pulley at one end and drives many accessories, such as generators, air conditioning compressors, booster pumps, etc. If it breaks, it won't damage any components, but the accessories it drives won't work, and the car will break down and won't be able to drive. If it is on a highway or in a wilderness area, although there is no damage to the car, it is also troublesome to not drive it, so regular replacement is also necessary.
How many kilometers does the vehicle need to replace these two belts? Many people have different opinions, and each model is also different. Please follow the recommendations in the maintenance manual. Take a look at the maintenance manual, it clearly states. The most conservative replacement cycle for most cars is three years or 60000 kilometers, with some cars exceeding this mileage. Many people only change cars after 100000 kilometers without breaking them, and they have also encountered individual cars that break just after 60000 kilometers. Personal driving habits vary, such as frequent heavy load driving, and differences in the quality of the belt itself, which can lead to differences in its lifespan. The safest thing is to immediately replace it at the manufacturer's recommended replacement mileage or time.
From: WONDEE Autoparts 2023-10-19