Causes of Oil Blowing Out the Blow-by Tube in a 1985 International Truck

[MikePhua]

The 1985 International truck is a heavy-duty vehicle widely used for various applications, but like any machine, it can experience engine-related issues over time. One such issue that may concern truck owners is oil blowing out of the blow-by tube. This can be puzzling, but understanding the potential causes and solutions is key to resolving the problem. This article explores common reasons why oil may blow out of the blow-by tube in a 1985 International truck and offers solutions for addressing these issues.
Common Causes

1. Engine Wear
   As the engine in a truck ages and accumulates more operating hours, various internal components, especially the piston rings, cylinder walls, and valve seats, may begin to wear. This wear can result in increased pressure within the cylinders. High pressure may cause oil and gas mixtures to pass through worn piston rings and into the combustion chamber, or they may escape through the blow-by tube, leading to oil being blown out.
   
2. Blown Head Gasket
   A blown head gasket can cause internal engine pressure to be unregulated, especially under high-temperature and high-pressure conditions. When a head gasket fails, gases and oil can leak into areas they shouldn’t be, which can result in oil being expelled through the blow-by tube or other parts of the engine.
   
3. Engine Overheating
   Overheating is a common cause of increased internal engine pressure. Prolonged high temperatures can cause the engine seals to degrade, particularly around the piston rings and cylinder walls. High temperatures may also alter the viscosity of engine oil, making it easier for oil to be pushed into the cylinders, which could eventually be expelled through the blow-by tube.
   
4. Oil Quality Issues
   Using low-quality engine oil or contaminated oil can contribute to the issue of oil blowing out of the blow-by tube. Poor-quality oil may not maintain proper viscosity under high temperatures, allowing more oil to enter the combustion chamber. Additionally, impurities in the oil can accelerate internal engine wear, exacerbating the problem.
   
5. Clogged Ventilation System
   If the engine's ventilation system, including the blow-by tube, becomes clogged or obstructed, oil and gases cannot be properly vented. This buildup of pressure can result in oil being forced out through the exhaust system or other engine parts. Blockages in the system are usually caused by oil sludge or other contaminants, and regular cleaning is essential to prevent such issues.
   

Solutions

1. Inspect and Replace Piston Rings
   Worn piston rings are a common cause of excessive blow-by and oil leaks. Regular inspection of the piston rings can identify wear and tear. If necessary, replacing the piston rings will help restore proper sealing between the pistons and cylinders, reducing pressure buildup and preventing oil from being blown out.
   
2. Check the Head Gasket
   If you suspect a blown head gasket, conduct a pressure test to confirm whether the gasket is damaged. If the head gasket is indeed faulty, it should be replaced immediately to restore proper sealing and prevent oil and gas from leaking into areas where they shouldn’t be.
   
3. Control Engine Temperature
   Maintaining the engine at a normal operating temperature is essential to prevent overheating. Regularly check the cooling system, including the radiator, thermostat, and water pump, to ensure they are functioning correctly. Using high-quality engine oil with good high-temperature stability is also important to maintain proper viscosity and reduce oil-related issues.
   
4. Use High-Quality Oil
   Always use high-quality oil that meets the specifications for your truck and replace the oil regularly. Good-quality oil will not only provide better lubrication but also reduce internal engine wear, which in turn reduces the risk of oil blowing out through the blow-by tube.
   
5. Clean the Ventilation System
   Regularly inspect and clean the engine's ventilation system, ensuring that there are no blockages in the blow-by tube or other parts of the ventilation system. A clean ventilation system will help maintain proper pressure levels and prevent oil from being forced out through the exhaust or blow-by tube.
   

Conclusion
The issue of oil blowing out of the blow-by tube in a 1985 International truck can be caused by several factors, including engine wear, a blown head gasket, overheating, poor oil quality, and a clogged ventilation system. By regularly inspecting and maintaining the engine, replacing worn components, using the right oil, and keeping the ventilation system clean, you can effectively address this problem and improve the performance and longevity of the vehicle.