The cylinder head is one of the most important parts of the engine. It plays a vital role in the efficient performance of the engine. It ensures the proper combustion of the air-fuel mixture. A cracked cylinder head can be a costly repair.
When your cylinder head is damaged or cracked, it produces different signs and problems. This article explains the cracked cylinder head symptoms, causes, and replacement cost.
What is a Cylinder Head?
A cylinder head is a most important part of an internal combustion engine installed on top of the engine block, forming the top of the combustion chamber.
The cylinder head is attached to the engine block with a gasket known as the head gasket. This gasket helps to prevent the leakage of engine oil and coolant into the combustion chamber and maintains proper compression.
The cylinder head contains the spark plug, ignition coils, fuel injector, intake, and exhaust valves.
The cylinder head enables the engine to operate at peak efficiency by linking to the exhaust and intake manifolds, facilitating the rapid combustion of the air-fuel mixture that drives the engine piston.
The intake manifold of your vehicle engine delivers air from the environment to the combustion chamber, where it mixes with fuel and combusts, producing exhaust gases that are then released by the exhaust manifold.
Proper functioning of the intake and exhaust valves, which control the flow of gases in and out of the engine, is crucial for smooth engine operation, as they must open and close at precise moments.
Under extreme conditions, a cylinder head may crack, leading to issues similar to those produced by a blown head gasket or a damaged engine block. A cracked cylinder head is more challenging to repair, and in most cases, the recommended solution is to replace it with a new one.
Symptoms of a Cracked Cylinder Head
A cracked cylinder head produces one or more of the following signs:
- Check Engine Light
- Low Coolant Levels
- White Smoke from Exhaust
- Oil and Coolant Mixture
- Oil Leakage
- Poor Engine Performance
- Overheating
- Engine Misfiring
1) Check Engine Light
A warning light may appear on your vehicle’s dashboard if the issue is significant enough. The check engine light may start to illuminate, particularly if your engine is misfiring, but a cracked cylinder head alone may not always trigger this warning.
Additionally, you may also see a high coolant temperature light or a low coolant level light if the coolant becomes lower than the specified limit. It’s essential to take these warning lights seriously and address them immediately.
Read More: Causes of Check Engine Light Illumination
2) Low Coolant Level
A reduction in the coolant level is one of the major signs of a cracked cylinder head. This reduction in the coolant levels may indicate a leak, which can be easily spotted on the cylinder head.
A crack in the diesel engine cylinder head could be the cause of this leak, leading to more long-term problems as the engine overheats due to insufficient coolant.
Read More: Causes and Symptoms of Coolant Leak
3) White Smoke from Exhaust
The engine contains different coolant lines running through the cylinder head to maintain optimal temperatures.
Coolant may seep into the engine cylinder if a crack occurs in the cylinder head, as previously mentioned. When this happens, the coolant will burn during the combustion process.
This results in white smoke, which is actually steam, emitting from the exhaust system through the exhaust pipe. This smoke may have a sweet scent due to the coolant. This dissimilar smell is unlike any other fluid that could potentially burn.
4) Oil and Coolant Mixture
A cracked cylinder head can cause symptoms similar to those of a blown head gasket. For example, both issues can lead to coolant and oil mixing.
But with a cracked cylinder head, exhaust gases may also enter the cooling system, which can be mistaken for oil mixing, except that it appears more like bubbles.
In any case, the coolant should resemble coolant, and motor oil should look like oil. If either appears unusual, it’s advisable to have it inspected further.
5) Oil Leakage
Oil plays a crucial role in lubricating the engine’s moving components, including the cylinder head.
A damaged or cracked cylinder head may lead to oil leaks, which may be most evident by a pool of oil under your car when it is parked for an extended period. This situation can be problematic, as coolant or oil might also seep into the combustion chamber if the crack is large.
Read More: Low Engine Oil Symptoms and Causes
6) Poor Engine Performance
One of the clear signs of a damaged or cracked cylinder head is poor engine performance. This problem is usually produced when the air-fuel mixture doesn’t combust efficiently in the combustion chamber.
You can easily observe this issue as the engine will not run as smoothly as before, and your engine may restart after multiple attempts.
7) Engine Overheating
When the coolant level decreases, the engine is at risk of overheating. When the coolant level becomes lower than the specified level, it becomes impossible to keep the engine oil cool when it circulates within the engine.
If your dashboard contains a temperature gauge, you may notice it begin to rise. Additionally, as mentioned earlier, the engine overheats warning light might turn on. It is essential not to drive your engine while it’s overheating, as doing so can cause further damage.
Read More: Causes of Engine Overheating
8) Engine Misfiring
In the combustion chamber, the combustion of the air-fuel mixture generates power.
A cracked cylinder head might not be able to establish the necessary conditions for proper combustion inside the engine cylinder, leading to incomplete combustion or misfiring. As a result, the engine may frequently stall while driving or fail to start altogether.
Causes of a Damaged Cylinder Head
The cylinder head of your engine is damaged or cracked due to one or more of the below-given causes:
- Overheating
- Faulty Water Pump
- Air in the Cooling System
- Failed Thermostat
- Prolonged Engine Stress
- Coolant Leak
- Physical Damage
1) Overheating
If your vehicle contains an internal combustion engine, it may overheat very quickly. As the name of the IC engine implies, it is designed to contain small, precise explosions.
However, a significant portion of the energy generated during combustion is not fully converted into kinetic energy to drive the vehicle but is instead lost as heat energy. This inherent heat generation can be lessened but never entirely eliminated.
Overheating is one of the major reasons of a cracked cylinder head. When your engine overheats, the engine components can be subjected to stress well beyond their intended heat tolerance.
Most cylinder heads are made of aluminum; they may warp or crack if the engine gets too hot. The engine usually overheats due to a faulty cooling system.
2) Faulty Water Pump
The water pump is used to properly circulate the engine coolant throughout the engine. When it goes bad, it doesn’t circulate the coolant properly. The coolant surrounding the water jackets in the cylinder block and head can become very hot, even if it remains cold in the radiator.
Without a functioning pump, coolant may only move by natural convection, which is much too slow to dissipate excess heat and can’t prevent the engine from overheating.
3) Air in the Cooling System
Air pockets in the cooling systems can lead to the formation of hot spots, where a specific area of the engine becomes significantly hotter compared to the area monitored by the temperature sensor. This occurs because air is less efficient at transferring heat compared to liquid.
If air becomes stuck in a location distant from the coolant temperature sensor, your sensor will be unable to detect the hot spot. As a result, you will be unaware that your vehicle is overheating until it’s too late and damage has occurred.
Moreover, an air leak in the cooling system can cause a drop in pressure. This reduced pressure makes the liquid coolant more prone to boiling at lower temperatures.
4) Failed Thermostat
Combustion engines work efficiently at their designed operating temperatures, which typically range between 190- and 210 degrees Fahrenheit (85 to 99 degrees Celsius)—hot enough to cause burns. A reduction in the operating temperature of the engine increases its fuel consumption, wear, and emissions.
A thermostat is used to prevent the coolant from moving from the radiator until it reaches the required temperature. Once the target temperature is achieved, the thermostat opens, permitting room-temperature coolant to flow through the engine and letting it cool the engine hot parts. This cycle repeats during engine operation.
If your thermostat is stuck open, the car may experience unusually low operating temperatures. This occurs because coolant continuously flows through the radiator, preventing the engine from reaching its optimal temperature.
Conversely, if your thermostat is stuck closed, the engine can overheat rapidly since the hot coolant has no means of dissipating heat. In some engines, you can temporarily utilize the heater as a small radiator. However, the effectiveness of this solution depends on the design of the cooling system and the heater core size.
5) Prolonged Engine Stress
Constantly running the engine under heavy loads or at high RPMs may lead to excessive stress on the cylinder head, increasing the chances of cracking over time.
6) Coolant Leak
When a significant amount of coolant leaks out, there may eventually be an insufficient amount left to adequately cool the engine.
It’s possible to lose a considerable amount of coolant before experiencing overheating, but it’s wise to routinely inspect the coolant tank and radiator to ensure they’re adequately filled.
If you detect coolant leaks, it’s highly recommended to examine your radiator cap, as it’s an inexpensive component that can have significant consequences if it malfunctions.
7) Physical Damage
Accident or poor handling during maintenance may cause physical damage to the cylinder head and leads to cracks.
Cylinder Head Replacement Cost
The replacement cost of the cylinder head varies according to the vehicle model, your engine model, and labor cost. The average replacement cost of the cylinder is from $700 to $4300.
How to replace a Cylinder Head?
FAQ Section
What is a cylinder head?
A cylinder head is part of an IC engine installed on top of the engine block, forming the top of the combustion chamber.
What is the function of a cylinder head?
The main function of the cylinder head is to form the top of the engine cylinder, housing internal parts such as fuel injectors, spark plugs, and intake and exhaust valves while also facilitating heat dissipation and ensuring proper compression in the engine.
What are the most common causes for a cylinder head to crack?
- Overheating
- Air in the cooling system
- Faulty water pump
- Prolonged engine stress
- Faulty thermostat
- Insufficient coolant
- Physical damage
What happens when a cylinder head cracks?
When the cylinder head cracks, your vehicle may produce different drivability issues such as engine overheating, poor fuel economy, engine stalling, hard engine start, and a quick reduction in the coolant level or engine oil.
What are the parts of the cylinder head?
- Rocker shaft
- Valve rocker arm
- Camshaft
- Valve
- Valve spring
- Stud hole
- Valve retainer
- Spark plugs
- Fuel injectors
- Coolant ducts
What are the symptoms of cylinder head problems?
- Illuminated check engine light
- Engine misfiring
- Oil and coolant mixture
- White smoke from the exhaust
- Oil leakage
- Poor engine performance
- Overheating
- Low coolant level
Can I drive with a bad cylinder head?
Yes, you can drive with a bad or cracked cylinder head, but it is not recommended. Driving with a bad cylinder head may cause further damage to the engine, overheating, engine stalling, poor performance, and potential breakdown. Therefore, it is recommended to fix the problem by a professional mechanic before continuing to drive the vehicle.
What are the symptoms of a bad cylinder head gasket?
- Overheating
- Misfiring
- Engine stalling
- Higher consumption of engine oil than usual
- Visible smoke from the exhaust pipe
- Rough idle
- Low Coolant Level