Blown Head Gasket on Mitsubishi Excavator: Diagnosing and Solving the Air Through Intake Problem

[MikePhua]

One of the most common and frustrating mechanical issues that can arise with heavy equipment is a blown head gasket. In the case of a Mitsubishi excavator, this problem can lead to air being pushed through the intake, which severely affects the engine's performance. This issue requires immediate attention, as it can lead to further damage to the engine components if not addressed promptly.
This article will explore the causes and symptoms of a blown head gasket in a Mitsubishi excavator, how it affects the engine, and the steps you can take to resolve the problem. We will also provide advice on prevention and real-world examples of similar issues in heavy machinery.
What is a Head Gasket and What Does It Do?
The head gasket is a critical component in any internal combustion engine, acting as a seal between the engine block and the cylinder head. It ensures that the engine’s combustion chambers are airtight, preventing leaks of coolant or oil and ensuring proper pressure in the cylinders. If a head gasket fails, it can lead to a number of issues, including coolant leaks, engine overheating, and, as in this case, air being pushed through the intake.
In a Mitsubishi excavator, a blown head gasket can have serious implications. The engine relies on a tightly sealed combustion chamber to operate efficiently. When the head gasket fails, the pressure created during combustion can escape into other areas, such as the coolant system or intake manifold, causing a range of operational problems.
Symptoms of a Blown Head Gasket in a Mitsubishi Excavator
The signs of a blown head gasket are often easy to miss, especially in heavy machinery where many issues may appear to be normal. However, there are a few key symptoms that can alert you to a head gasket failure:

1. Air Being Pushed Through the Intake
   This is one of the clearest signs that there is an issue with the head gasket. When the gasket blows, the compression in the cylinder can force air into the intake manifold. This can cause irregular engine behavior, including stuttering or misfiring, and may even cause the engine to stall under load.
   
2. White Smoke from the Exhaust
   If coolant is leaking into the engine’s combustion chamber, it will burn off and produce white smoke from the exhaust. This is a clear indicator that the head gasket has failed.
   
3. Loss of Coolant
   A blown head gasket can cause coolant to leak into the engine’s cylinders, leading to a noticeable drop in coolant levels. If you notice a sudden loss of coolant without any obvious leaks, this could be a sign of a head gasket failure.
   
4. Overheating Engine
   As the head gasket fails, it can cause a loss of coolant or allow coolant to leak into the engine, resulting in overheating. If the engine temperature rises beyond normal operating levels, the head gasket may be the culprit.
   
5. Rough Idle and Engine Misfire
   Air leaking through the intake or coolant leaking into the cylinders can cause engine misfires and rough idling. If the engine is not firing properly, this could indicate a head gasket issue.
   

Causes of a Blown Head Gasket
Several factors can lead to a blown head gasket in a Mitsubishi excavator, and many of them are preventable with regular maintenance:

1. Overheating
   The most common cause of a blown head gasket is engine overheating. When an engine runs too hot, the metal components expand and can warp, which puts additional pressure on the head gasket. This can cause the gasket to fail, especially if the coolant system is not working properly.
   
2. Poor Cooling System Maintenance
   A malfunctioning radiator, water pump, or clogged coolant lines can cause the engine to overheat, leading to a blown head gasket. Regular inspection of the cooling system is essential to avoid this problem.
   
3. Excessive Engine Pressure
   High engine pressure, which can result from improper combustion or a buildup of exhaust gases, can cause the head gasket to fail. This can be exacerbated by problems such as clogged air filters or faulty turbochargers.
   
4. Improper Torque on Head Bolts
   If the cylinder head bolts are not torqued properly during installation, it can cause uneven pressure on the head gasket, leading to failure. It's important to follow manufacturer specifications for proper torque settings when assembling the engine.
   
5. Aging or Wear and Tear
   Over time, the head gasket can deteriorate due to normal wear and tear. As the gasket ages, it becomes more prone to failure, especially in older equipment that has seen heavy use.
   

Steps to Diagnose a Blown Head Gasket
If you suspect that your Mitsubishi excavator has a blown head gasket, you can follow these diagnostic steps to confirm the issue:

1. Check for White Smoke
   Start the engine and observe the exhaust. If white smoke is coming out, this is a strong indicator that coolant is leaking into the engine and being burned off.
   
2. Perform a Compression Test
   A compression test can help determine if there is a loss of pressure in the cylinders. If the compression is lower in one or more cylinders, this could suggest a blown head gasket.
   
3. Inspect the Coolant and Oil
   Check the coolant and oil for signs of contamination. If the oil appears milky or there is coolant in the oil, this is another sign of a blown head gasket.
   
4. Look for Air in the Cooling System
   Air bubbles in the coolant reservoir or radiator can indicate that combustion gases are entering the cooling system, which is a common symptom of a blown head gasket.
   

Repairing a Blown Head Gasket
Repairing a blown head gasket is a complex and time-consuming task, often requiring disassembly of the engine. Here are the general steps involved:

1. Remove the Engine Components
   Begin by draining the coolant and removing the components that obstruct access to the cylinder head. This may include the intake and exhaust manifolds, air filters, and other components.
   
2. Inspect the Cylinder Head and Block
   Once the cylinder head is removed, inspect it for warping, cracks, or other damage. The engine block should also be checked for any signs of damage.
   
3. Replace the Head Gasket
   If the head gasket is damaged, it will need to be replaced with a new one. Ensure that the new gasket is the correct size and type for your specific Mitsubishi excavator model.
   
4. Reassemble the Engine
   After the new gasket is installed, reassemble the engine components, making sure to properly torque the cylinder head bolts and follow all manufacturer guidelines.
   
5. Check for Leaks
   Once the engine is reassembled, run it for a short time and check for any leaks. This includes checking the coolant system and exhaust for any signs of continued issues.
   

Preventing Future Head Gasket Failures
While some head gasket failures are unavoidable, there are several preventive measures you can take to extend the life of your Mitsubishi excavator and avoid future issues:

1. Regular Cooling System Maintenance
   Regularly check and maintain the cooling system, including the radiator, hoses, water pump, and coolant levels. Ensure that the system is functioning efficiently to prevent overheating.
   
2. Monitor Engine Temperature
   Always keep an eye on the engine temperature, especially during heavy-duty operation. If the engine begins to overheat, take immediate action to prevent damage.
   
3. Follow Proper Torque Specifications
   When assembling or servicing the engine, always follow the manufacturer's torque specifications for the cylinder head bolts. This helps prevent uneven pressure on the head gasket.
   
4. Avoid Overloading the Excavator
   Operating the excavator within its rated load limits can prevent excessive strain on the engine, reducing the risk of overheating and head gasket failure.
   

Conclusion
A blown head gasket is a serious issue that can cause significant damage to your Mitsubishi excavator. Understanding the symptoms, causes, and repair process is crucial to keeping your equipment in good working order. By regularly maintaining the engine and cooling system, monitoring the temperature, and following proper procedures for engine assembly, you can prevent future head gasket failures and ensure the longevity of your machinery. Remember, early detection and prompt repair are key to minimizing downtime and keeping your excavator running smoothly.