What would cause the pistons to hit the valves?

Your car’s engine consists of various parts with different purposes. Piston and valves are two crucial parts of the engine and sometimes might collide, causing damage to the other and the engine.

Due to various circumstances, the valves can hit the piston and bend it or cause slight damage. But before we jump into their collision, let us learn a little about the two parts.

A piston is a constituent of countering pumps, engines, hydraulic chambers, gas compressors, and pneumatic rolls, among other comparable appliances.

A vehicle’s engine’s function is to transmit force from intensifying gas in the container to the crankshaft through a connecting rod or piston rod.

On the other hand, a valve is a natural object or a device that controls and directs the flow of fluid in the engine by opening and closing or incompletely thwarting various hallways.

From the definition of a piston and valves, we can see a connection between them, vital parts of the engine. Therefore, they might collide in the process. In most cases, the piston hits the valves, but what could be the cause?

There are various causes like:

  • A bad timing belt
  • Failure of a tensioning device
  • A wrecked timing chain
  • A shattered timing gear
  • Anything significantly disrupting the introductory valve scheduling on a meddling engine.

Keep reading to learn more about what would cause the piston to hit the valves. Get into the details and understand the signs, causes, what happens when the incident occurs, and the event results.

What Causes the Pistons to Hit the Valves?

The leading cause of the piston hitting the valve is disruption of the valve by any means. When the valve is disrupted, it will remain constant while the piston continues to function, resulting in a collision between the two.

When the two parts are correctly working, they never meet because the piston transfers fluid by pumping it while the valves allow the liquid to pass.

Therefore, when the piston rises, the valves rise too. So, if the valves fail, the piston will hit it. This means that anything causing failure of the valves causes a collision between the valves and the piston.

The causes are many, but we’ll dig deeper into these four;

1. A Bad Timing Belt

The timing belt powers the camshaft, which is responsible for the opening and closing of the valves. Therefore, if the timing belt strips or breaks, the camshaft stops operating and, in the process, affects the functioning of the valves.

However, the crankshaft does not stop spinning. It spins at 1000 rotations every minute, and since it is responsible for the piston’s operation, the piston continues to operate normally. So, the piston will hit the stagnant valves while it works.

2. Failed Tensioning Device

Tensioning device functions by tightening the timing belt. Therefore, the timing belt loosens if the timing device fails, making the camshaft out of phase and affecting the valves. When the valves are affected, they remain dormant while the piston remains functional, thus hitting them.

3. A Wrecked Timing Chain

A wrecked timing chain stops the valves from functioning and bends them, and since the piston is still performing, it hits the valves, potentially ruining the engine. If the vehicle is not operating, the machine will not start due to insufficient compression.

4. A Shattered Timing Gear

A timing gear works in hand with the timing belt. Therefore, the timing belt fails when the gear breaks, leading to valve failure, resulting in a collision with the piston.

What Happens if a Valve Hits a Piston?

Due to a particular cause that can only be realized after the diagnosis of the engine, the valve might hit the piston. In most cases, the valves end in the losing point. A piston is more robust than a valve and functions under tremendous pressure.

Therefore, the valves might bend while the piston gains some scratches. This clash of the Titans leads to engine failure leaving with an option of replacing the valves and the piston if it is severely damaged or replacing the engine if the damage is extensive.

Depending on the extent of the damage, your mechanic will advise you on the best solution for your car.

What Happens to the Pistons After They Have Hit the Valves?

When the piston hits the valves, it is rarely affected though it will incur slight damage. The collision might rub off the carbon buildup on the piston in most cases.

Remember, the valves are never under pressure, so they get damaged when the crash occurs, while the piston only sustains slight damage on the surface.

How can you Tell the Pistons are Hitting the Valves?

Learning more about vehicles is very important. It helps you sense a rising problem by studying the car’s different signs before the problem becomes severe.

When a piston starts hitting valves, your car shows some signs, and if you understand the symptoms, you can stop the vehicle to prevent severe engine damage.

Below are the most common signs cars show when the piston starts to hit valves.

  • The car will have very coarse idling
  • The engine will be choking
  • The vehicle will produce unusual sounds like rough rattling
  • The engine will lose power and will start to underperform.
  • When you check the heads of the piston, you might notice scratches, and they might be wet or spongy.

When Piston Hits the Valves, Does it Lead to Total Engine Failure?

The impact will determine the extent of the engine damage. Sometimes, the valves might not be severely damaged or bent if realized earlier.

Therefore, there will be no total engine failure, but that does not mean you continue driving since you will only cause more damage to the engine.

However, if the impact is high, the valves can bend and affect the cylinder, leading to a total engine failure. This mostly happens if the incident occurs while the car is in motion.

In this case, the timing belt jumps, and due to the high rotations of the crankshaft, the piston hits the valves, severely bending them and affecting the valve cylinder.

Can this issue be repaired? Or a new Engine is Needed for Replacement?

Some mechanical problems are beyond repair and require engine replacement. Luckily, this problem can be repaired without replacing the engine. If the valves are bent and the valve cylinder is not affected, you will only need to replace the valves.

Also, the crash might have severely damaged the piston. Therefore, it will need replacement too. However, pistons rarely incur severe damage and can be reused even with slight wear.

Sometimes, the vehicle’s engine might have other internal severe problems which might surface after the incident. Therefore, the engine will be severely damaged and require replacement.

For instance, due to a lack of proper oiling, the engine parts might gain rust, and when this issue happens, the components involved initially have rust problems. So the damage will be severe.

Unless you understand the extent of the damage, you can barely tell the actual cost of this repair. However, since over 90 percent of these damages require valve repairs, it can cost more than $1000, including labor.

This is the cost of replacing one head of the broken valve. Therefore, if the engine has other problems, the price will be higher.


Various causes can result in a collision between piston and valves, and in most cases, the valves incur severe damage. All the reasons revolve around the timing belt failure leading to the valve’s failure to function. This creates a collision possibility with the piston, which continues to operate.

Depending on the impact, the valves might be seriously damaged, leading to a total engine failure. However, you can prevent severe damage if you interpret the vehicle’s signs.

Therefore, it would be wise of you to learn the different signs and be able to interpret the meaning to avoid this and other mechanical problems that can not only put your vehicle at risk but also your life.

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