Engine water hammer: causes and consequences. How to avoid engine water hammer

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Engine water hammer: causes and consequences. How to avoid engine water hammer
Engine water hammer: causes and consequences. How to avoid engine water hammer

The internal combustion engine is the heart of the car. The service life of the unit depends on the conditions under which it is used. But there are breakdowns that have nothing to do with the current state of the motor. This article will discuss what an engine water hammer is, why it happens and how to avoid this kind of breakdown. But first things first.

car in the water
car in the water

What is water hammer?

Normal operation of the power unit of the car does not imply the presence of water in the latter. Water hammer is an increase in internal piston pressure hundreds of times. This is due to moisture getting into the cylinders. If we take into account that water is practically an incompressible liquid, then something like the following happens. During the compression stroke, the piston moves to its extreme point, but encounters an obstacle in its path in the form of water. It cannot complete the cycle, which is why water hammer occurs.

You don't need a lot of water in the cylinders for this to happen, just enoughits small amount. Since the piston is trying to complete the compression cycle, the studs break and break the cylinder head block, the connecting rods bend, etc. Block rupture is the most serious problem in which the repair of an internal combustion engine is impractical, it is easier to buy a new or contract engine.

How does an engine water hammer occur?

What is it, we have already figured out, and now let's talk a little about something else. How does moisture get into the motor? This question interests many, but in fact everything is extremely simple. In 80% of cases, water is taken from outside. For example, through the intake manifold when driving through deep puddles. "Drowned" also almost all get a water hammer, unless, of course, you perform some actions before launching.

SUV with snorkel
SUV with snorkel

But there is another 20% that not everyone knows about. The fact is that a car is a rather complex system consisting of many components and assemblies. The engine is liquid-cooled. Antifreeze circulates through special channels in the cylinder head. If the gasket burns out, then fluid enters the cylinders. Sometimes water hammer occurs due to the overflow of fuel into the combustion chamber. This happens extremely rarely, but such a possibility should not be ruled out. That is why it is necessary to periodically service the fuel and injector.

Consequences of engine water hammer

A similar problem can happen to any of us. Fortunately, engine overhaul is not always required. Depending on the situation in which the breakdown occurred, appropriatemeasures. For example:

  • Water hammer at cold running and low speeds. In this case, the consequences are often avoided.
  • When hit at high speeds of the crankshaft, the power unit is seriously damaged. Connecting rods and pistons fail, as well as the crankshaft itself and its liners.
  • On the middle stroke - this case is characterized by a slight curvature of the connecting rod. During operation, it will touch the counterweight of the crankshaft. The longer you drive like this, the more serious the consequences will be.
  • effects of water hammer
    effects of water hammer

It is worth noting that an engine overhaul is impossible if the piston has pierced the cylinder walls. It should be understood that after a problem occurs, the motor often continues to work, it is better to immediately send it for repair. In this case, there is a high probability of getting by with little blood. Almost always the crankshaft does not receive damage. It fails during the operation of the power unit after a water hammer, if the connecting rods are bent and there are other deformations.

Breakage Prevention

We have already figured out how the engine water hammer occurs. Based on this, certain measures can be taken. For example, it is not recommended to drive into deep puddles more than the middle of the wheels, especially at high speed. After all, the ingress of water under pressure into the air intake will inevitably lead to water hammer. Some modern SUVs are equipped with so-called snorkels. These are two-channel devices installed in a vertical position. One channel for air supply, andthe second - removal of crankcase gases.

Cars are almost never equipped with snorkels, the owners are forced to install them themselves. Put them under the wings at maximum height. Optimally - 80-100 centimeters from the ground. It is also recommended to periodically check the air duct for mechanical damage. Sometimes cracks and punctures in the air filter housing cause moisture to enter the engine even during heavy rain.

water hammer recovery
water hammer recovery

If water hammer still happened

The first step is to inspect the air duct. To do this, remove the air filter box and look for the presence of moisture. It must be removed and the filter dried. The second action is unscrewing the candles, this applies to gasoline power units. You can try turning the crankshaft by hand. If hooks are heard or noticeable during the cycle, then we call a tow truck and go to the service station. In the case when the deformations are insignificant or absent at all, you can try to crank the engine with a starter. If knocks and other extraneous metallic sounds are heard in the process, then it is better not to force the motor anymore. Well, when everything is in order, we start up and go to the service station. A car service after any, even the weakest water hammer, is still worth a visit, because if water gets into the engine, then it needs to be removed from there and the cylinder-piston group should be troubleshooted.

Another interesting point is that diesel engines suffer more from water hammer. This is due to the fact that their combustion chamber is smaller, and the pressure is an order of magnitude greater. Therefore, with enough water in the cylinder, it can easily break the block.

connecting rod deformation
connecting rod deformation

Main symptoms

We figured out the causes of the water hammer, so I would like to say a few words about how to understand that such a breakdown has occurred. After all, a knock in the motor may not be due to moisture. The first step is to inspect the intake manifold and air filter. The latter, due to the presence of moisture, is very often deformed. It is worth noting that water dries quickly, so you need to look for it immediately after a malfunction occurs.

Next you have to remove the cylinder head. In which particular cylinder there was a water hammer, it is immediately noticeable by the increased soot strip. This is due to the fact that the piston on the bent connecting rod cannot complete the compression stroke, and the soot band grows. If the connecting rod bends, then the piston slightly shifts to one of the cylinder walls. This leads to displacement and streaks of soot on the wall, which is quite difficult to miss.

More symptoms

As noted above, the motor does not always receive critical damage. In some cases, the connecting rod can completely tear off the piston, or it can slightly deform it at the base. Therefore, the inspection of the connecting rod must be carried out as carefully as possible. It is recommended to pay attention to the cylinder walls. Most likely, they will have characteristic scuffs and scratches, which is evidence of a bent connecting rod.

filter drying
filter drying

When the piston does not work properly, this contributes to increased wear of one ofcrankshaft bearings. But this is visible only in the case of a complete overhaul of the power unit. If there was a blow, then in the filled cylinder there is usually more soot than in all the others. All these signs of an engine hydraulic shock are almost never found separately. Their combination suggests that the internal combustion engine needs to be repaired.

Overhaul of the power unit of the car

In 80% of cases, such repairs will still be needed. But the cost will depend on the nature of the damage. If only the connecting rods are bent, then the piston-rod group is being replaced. Even those jobs don't come cheap. A lot also depends on the engine. If this is some kind of rare power unit in your city or region, then you should mentally prepare for high costs.

But such a plan breakage is not so bad. Very often, engine overhaul is not limited to replacing connecting rods and pistons. If the block is broken, then the price tag for repairs increases several times. You will need to remove the power unit from the car, sort it out. Replace the piston and buy a new block. In most cases, the price of such a repair is equal to the purchase of a contract power unit. What is better, everyone decides for himself. After all, many drivers are able to sort out their motor on their own. In this case, it is advisable to carry out repairs, having previously purchased the necessary spare parts.

motor after water hammer
motor after water hammer


How to avoid engine water hammer? Everything is simple here - deep puddles must be driven as slowly as possible. Optimal speed - no more than 7kilometers per hour. This is especially true for understated cars. Do not try to swim across deep puddles by car that completely cover the tires. In any case, this will negatively affect the performance of the vehicle, but whether the engine jams or not, how lucky.

Water hammer is one of the most serious breakdowns of the power unit, along with insufficient lubricants and overheating. In order for the engine to work for a long time and properly, it must be operated in a gentle mode, not to give high revolutions to the cold, not to drive for a long time at high speed and not to drive into deep puddles and pits. Keep an eye on the amount of oil and change it in a timely manner, and if you love cross-country driving, then you should definitely install a snorkel.