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Cracked Cylinder Liner (Symptoms & Causes)

✔ This article has been fact checked.

The cylinder liner (also known as a cylinder sleeve) is a crucial component of an internal combustion engine. It is an essential component of the engine block and serves as the bore in which the piston moves.

A cracked cylinder liner in an engine is a fracture or break in the surface of the liner that separates the cylinder from the engine block. This can be caused by excessive wear, improper manufacturing, high pressure or thermal stress, or a lack of lubrication.

In this article, we will discuss the symptoms and causes of a cracked cylinder liner, as well as the various repair options available.

Table of Contents:

a cracked cylinder liner with a red circle showing the crack up close

What Is a Cylinder Liner?

A cylinder liner is a cylindrical metal sleeve that is fitted inside the engine block. The piston moves up and down within this sleeve.

The cylinder liner is typically made of cast iron or aluminium, sometimes it's a different material than the rest of the engine. It serves as a barrier between the combustion chamber and the engine block.

different types of cylinder liners

Its Purpose

The primary purpose of the cylinder liner is to provide a smooth surface for the piston to move within. A liner also helps maintain compression and prevents leakage of coolant and oil into the combustion chamber.

It also helps in controlling the temperature of the engine, preventing overheating and damage to other components.

diagram showing the cylinder liner inside of an engine

Symptoms of a Cracked Cylinder Liner

There are several warning signs that can suggest a cracked cylinder liner in an engine. These symptoms can vary in severity and can have a significant impact on the performance and overall function of the engine.

Bear in mind that these symptoms can also be caused by other issues with the engine and may not always 100% indicate a cracked liner.

  1. Oil in the coolant

  2. Coolant in the oil

  3. Low compression

  4. White exhaust smoke

  5. Visible crack in the liner

1. Oil in the Coolant

One of the key symptoms of a cracked cylinder liner is the presence of oil in the coolant system, it can leak through any cracks and enter the water jacket (the flow of coolant) surrounding the combustion chamber.

This can lead to contamination of the coolant and could even cause damage to the engine components, such as the radiator and hoses. The coolant may also become discolored and have a milky appearance due to the oil mixing with it.

2. Coolant in the Oil

Another symptom of a cracked cylinder liner is coolant in the oil system. This occurs when coolant leaks into the oil system through the crack in the liner, resulting in the oil becoming contaminated with coolant.

This can cause damage to the engine components, such as the bearings, and can lead to a decrease in engine performance.

You can inspect the oil filler cap for a milky or frothy appearance, this indicates the presence of water and coolant in the oil.

a milky oil filler cap
An example of what a milky oil filler cap looks like.

3. Low Compression

A cracked cylinder liner can also result in a loss of compression in the engine. This occurs because the crack in the liner allows the air and fuel mixture to escape from the combustion chamber, reducing the compression pressure.

This can cause a drop in performance, such as a decrease in power and acceleration, and can result in the engine misfiring or stalling.

Escaping combustion mixture can also increase pressure within the coolant or oil system and could result in further damage. You can check for exhaust in the coolant with a combustion leak tester and this will give you an indication of whether or not you have a crack in the liner.

Watch the video below to learn how to use a combustion leak tester.

4. White Smoke From the Exhaust

Another symptom of a cracked cylinder liner is white smoke emitting from the exhaust. This occurs when coolant enters the combustion chamber through the crack in the liner, causing white smoke to be emitted from the exhaust.

This can be a clear indicator of a crack in the liner and should be addressed as soon as possible to prevent further damage to the engine.

white smoke coming a car exhaust tailpipe

5. Visible Crack in the Liner

In some cases, a crack in the cylinder liner may be visible, and a diagnosis can be made by a visual inspection.

You can use a borescope to search for cracks in the cylinder sleeves but in most cases, a more thorough inspection is necessary to determine the presence of a crack. This inspection is usually carried out by removing the cylinder head and visually inspecting for cracks and fissures.

A visible crack in the liner is a clear indication that the liner is damaged and should be addressed to prevent further damage to the engine.

Causes of a Cylinder Liner Cracking

Cylinder liners are critical components of an engine and are subjected to extreme conditions, including high temperatures, pressure, and stress.

Over time, these factors can take a toll on the cylinder liners and cause them to crack, leading to serious consequences for the engine's performance and longevity.

There are several potential causes of cylinder liner cracking, including those listed below.

  1. Weak cylinder liners

  2. Excessive power

  3. Overheating

  4. Heat spots and swelling

  5. Incorrect installation

  6. Knocking

  7. Combustion chamber contamination

1. Weak Cylinder Liners

One cause of cracking can be the use of weak or low-quality materials in the manufacture of the cylinder liners. This can make them more prone to cracking and damage under the intense conditions of the engine.

A notable example is the Mk2 Ford Focus ST having weak liners. Many owners of this vehicle shim the cylinders to add strength in an attempt to prevent this issue.

2. Excessive Power (Tuning)

Another cause of cylinder liner cracking can excessive power produced by the engine. When the engine is producing more power than it was designed to handle, such as when remapped and tuned, it can result in excessive stress on the cylinder liner, leading to cracking.

3. Overheating

Overheating of the engine can also cause excessive expansion and contraction of the cylinder liner, leading to it cracking. This can be a result of issues with the cooling system, such as a clogged radiator, a faulty thermostat, low coolant, etc.

infographic: signs of a car overheating

4. Heat Swelling and Heat Spots

Heat swelling and heat spots are conditions that occur when certain areas of the engine are overheating and causing localised damage to the cylinder liner.

In this case, if the liner heats up more in one area than another, it can lead to the metal expanding and contracting at different rates, causing it to crack.

Heat spots can be caused if the cooling system is not working as it should, such as:

  • if the water pump isn't working

  • the coolant is low

  • air has entered the system

  • the thermostat is faulty

  • the radiator is clogged

5. Incorrect Installation of Pistons or Liners

If the pistons or cylinder sleeves are not installed correctly, this can cause excessive stress on the liner and lead to cracking. This can be the result of improper installation techniques or the use of incorrect parts.

6. Engine Knocking

Engine knocking is another factor that can cause excessive vibration and stress on the cylinder liner, leading to cracking. Knocking can be caused by many issues, such as with the engine's fuel delivery system, the use of low-quality fuel, or other factors.

7. Contaminants in the Combustion Chamber

Contaminants in the combustion chamber, such as dirt, dust, and other debris, can cause corrosion and damage to the cylinder liner over time. This can potentially result in cracking and other types of damage to the liner.



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