A vehicle’s cylinder head is mounted to the top of the engine block. The head gasket is located between the two components, designed to seal them together.
The cylinder head creates a space for the spark plugs and the intake and exhaust valves. In engines with an overhead cam layout, the cylinder head also has a spot for the camshaft.
There are numerous passageways—usually called tracts or ports—within the cylinder head. Some of these tracts allow airflow to the inlet valves, while others create a route for the exhaust gasses leaving the motor.
With the cylinder head in place, the tops of the cylinders are sealed to create combustion chambers. Spark plugs stick out from the cylinder head into the combustion chamber to initiate ignition.
The valves atop each cylinder are opened by the camshaft. The intake valve allows air and fuel to mix in the cylinder before it closes. The air-fuel mixture compresses when the piston moves up inside the cylinder. Spark plugs then ignite this compressed fuel.
Read this: All About Camshafts and How They Work
The expanding gasses cause the piston to move away from the cylinder head. Following the combustion stroke, the piston returns toward the cylinder head, allowing the exhaust valve to open so the gasses can escape. The timing belt or chain ensures everything happens at the correct interval.
The cylinder head is responsible for these tasks:
The following components are a part of the standard cylinder head.
In most cases, cylinder head failure is due to the engine overheating. This usually comes from a coolant leak, head gasket failure, or a restriction preventing coolant flow.
The metal heads expand as the engine rapidly heats up and contract as the engine cools. This can lead to cracks in the cylinder head. The vehicle should be able to handle rapid cooling and heating, but this problem is more common when the cylinder head and engine block are made from two different materials. For example, the vehicle may have a cast iron engine block and an aluminum cylinder head. As the metals contract and expand at different rates, cracks can occur in the head.
When the cylinder head cracks or fails, you may notice one or more of the following symptoms:
Additionally, if the coolant seeps past the gasket and contaminates the engine oil, you will see a milky substance under the oil cap. It usually has the thickness of a milkshake.
Read this: Identifying Common Engine Leaks
How to Fix a Bad Cylinder HeadDepending on the severity of the damage, it may be possible to repair the crack so you can avoid a complete replacement. Here are the options to consider.
Once you know there’s a problem with the cylinder head, it’s best to stop driving and have it fixed. With coolant leaking or a failed gasket, the engine will overheat. Significant engine damage is sure to follow. It’s much cheaper to replace the cylinder head than to add an engine rebuild or replacement on top of the repair cost.
The cost to replace a vehicle’s cylinder head depends on what type of car you drive and who performs the labor. If you do it yourself, the cost may only be around $2,000. Professional labor would add around $1,500.
The cylinder head is meant to last the engine’s lifetime, so it’s not a common replacement. By maintaining the vehicle, you can prevent cylinder head failure. It’s essential to perform all of the necessary oil changes and to fix any coolant leaks as they occur so the motor doesn’t overheat.
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