Blow by in a diesel engine occurs when combustion gases escape past the piston rings and enter the crankcase. This issue can lead to reduced engine performance, increased oil consumption, and potential long-term damage if left unaddressed. Understanding the causes and solutions for blow by is essential for maintaining the efficiency and longevity of your diesel engine.
This guide on how to fix blow by on a diesel engine will walk you through the steps to identify, diagnose, and fix blow by to keep your engine running in optimal condition.
Why Does Blow by Happen
Blow by can happen for various reasons, including worn or damaged piston rings, improper installation of the rings, inadequate ring tension, and excessive cylinder wear. Over time, these factors can cause gaps between the rings and the cylinder walls, allowing combustion gases to escape into the crankcase.
You may also experience blow by if the engine is overfilled with oil or if the PCV (Positive Crankcase Ventilation) system is malfunctioning. In both cases, excessive pressure within the crankcase can force gases out through any available openings.
Needed Materials
New Piston Rings:
If the cause of the blow by is worn or damaged rings, then replacement rings will be necessary. Make sure to purchase the correct size and type for your specific engine.
Piston Ring Compressor:
A piston ring compressor helps compress the rings for easier installation. It can also help ensure that the rings are properly seated in the cylinder.
Cylinder Hone:
If excessive cylinder wear is causing blow by, honing may be necessary to restore a smooth surface for the new rings to sit against.
Gasket Replacements:
In some cases, replacing gaskets such as the head gasket or valve cover gasket may be necessary when fixing blow by.
9 Simple Methods on How to Fix Blow by on a Diesel Engine
Method 1: Replace Worn or Damaged Piston Rings
The most common cause of blow by is worn or damaged piston rings. To fix this issue, you will need to replace the rings with new ones.
- Remove the engine head and valve cover to access the pistons.
- Use a piston ring compressor to compress the old rings and remove them from the cylinders.
- Install new rings, making sure they are properly seated in their grooves.
- Reassemble the engine head and valve cover.
Method 2: Check Ring Tension
If the blow by is caused by insufficient ring tension, you may be able to fix it without replacing the rings.
- Remove the engine head and valve cover to access the pistons.
- Use a feeler gauge to check the gap between each ring and its groove on each piston. The gap should be within manufacturer specifications.
- If necessary, use a ring expander tool to slightly increase the tension of the rings.
- Reassemble the engine head and valve cover.
Method 3: Hone Cylinders
If excessive cylinder wear is causing blow by, honing may be necessary to restore a smooth surface for the new rings to seat against.
- Remove the engine head and valve cover to access the pistons.
- Use a cylinder hone tool with honing oil to smooth out any imperfections in the cylinders.
- Clean and dry the cylinders before reassembling the engine head and valve cover.
Method 4: Reduce Engine Oil Level
If blow by is occurring due to an overfilled oil level, this issue can be resolved by simply draining some of the excess oil.
- Locate the drain plug on the bottom of the engine oil pan.
- Place a large container underneath to catch the drained oil.
- Remove the plug and let excess oil drain out until it reaches the recommended level on the dipstick.
- Replace the drain plug and check the oil level again after running the engine for a few minutes.
Method 5: Check PCV System
If your diesel engine has excessive blow by, it may be due to a malfunctioning PCV system.
- Locate and inspect all components of the PCV system, including hoses and valves, for any signs of damage or blockages.
- Clean or replace any damaged components.
- Reassemble the system and check for proper operation.
Method 6: Replace Gaskets
In some cases, blow by may be caused by faulty gaskets such as the head gasket or valve cover gasket.
- Remove the engine head and/or valve cover to access the gaskets.
- Clean and inspect all surfaces before installing new gaskets.
- Apply a thin layer of gasket sealant to ensure a proper seal.
- Reassemble the engine head and/or valve cover.
Method 7: Upgrade PCV System
If your diesel engine is experiencing frequent blow-by, consider upgrading the PCV system to one that is more efficient.
- Research and purchase a high-quality, compatible PCV system for your engine.
- Follow manufacturer instructions for installation.
- Monitor for any improvements in blow-by.
- Consider upgrading other engine components if necessary.
Method 8: Perform Regular Maintenance
Regular maintenance is crucial in preventing and addressing blow-by in a diesel engine. Staying proactive can help identify issues before they worsen and ensure the engine’s efficient operation.
- Regular oil changes should be performed according to the manufacturer’s recommendations to prevent oil contamination and buildup that can exacerbate blow-by.
- Inspect the piston rings, cylinders, and PCV system during routine servicing for signs of wear or damage.
- Keep air filters clean and replace them when necessary to avoid debris from entering the engine and causing excessive wear on piston rings and cylinders.
- Use the manufacturer’s recommended oil grade and additives to help maintain proper lubrication and minimize internal engine wear.
- Monitor engine performance and promptly address any unusual noises, excessive smoke, or loss of power.
Method 9: Seek Professional Assistance
If the above methods do not effectively fix blow-by, it is best to seek professional assistance from a mechanic or diesel engine specialist. They have the expertise and equipment to accurately diagnose and address any underlying issues causing blow-by in your engine. Additionally, they can advise on proper maintenance practices to prevent future occurrences of blow-by. Remember, regular maintenance and timely repairs are key to keeping your diesel engine running smoothly for years to come.
Following these simple methods on how to fix blow-by on a diesel engine can help you effectively fix blow-by in your diesel engine and prevent further damage. Remember to always prioritize regular maintenance and address any issues promptly to keep your engine running at its best.
Additional Tips
- Blow by can also be caused by worn valve guides or seals, so it’s essential to check these components as well if other methods do not resolve the issue.
- Always wear protective gear when working on a diesel engine, including gloves and safety glasses.
- If using any chemicals or solvents during the repair process, make sure to dispose of them properly and according to local regulations.
- When reassembling components, always torque bolts to manufacturer specifications to ensure proper tightness and avoid damaging the engine.
- Consider investing in a blow by test kit for regular monitoring of your engine’s performance. This can help catch any issues early on before they become more severe.
Frequently Asked Questions
Q: Can Blow by Be Fixed Without Replacing the Rings?
A: Yes, depending on the cause of the blow by. If it is due to insufficient ring tension, you may be able to fix it with a ring expander tool. However, if the rings are damaged or worn, replacement may be necessary.
Q: How Much Blow by is Normal?
A: A small amount of blow by is normal in a diesel engine, but excessive amounts can indicate an issue that needs to be addressed. It’s essential to regularly check and monitor your engine for any changes in the level of blow by.
Q: Is Blow by Dangerous for My Engine?
A: Yes, excessive blow by can lead to increased wear on engine components and ultimately result in engine failure if left unaddressed. Regular maintenance and prompt repairs are crucial in preventing potential damage from blow by. So, it is always suggested that you take your vehicle to a professional mechanic if you notice any signs of excessive blow by.
Q: Can Blow by be Prevented?
A: While some factors, such as age and wear, cannot be completely prevented, regular maintenance and proper engine care can help reduce the occurrence and severity of blow by. Properly maintaining your PCV system, using the correct oil grade and additives, and avoiding overfilling the oil level are all essential steps in preventing blow by. Regular inspections and addressing any issues promptly can also help prevent excessive blow by. If you have any concerns or questions about your engine’ blow by, it’s always best to consult a professional mechanic for advice.
Conclusion
Blow by in a diesel engine is a common issue, but with the right approach, it can be effectively addressed and managed. By using the methods on how to fix blow by on a diesel engine outlined above and committing to regular maintenance, you can prevent further damage and ensure your engine operates efficiently for years to come.
Always prioritize monitoring engine performance, promptly address any unusual symptoms, and consult a professional when necessary. With diligence and care, you can extend the lifespan of your engine and maintain its reliability.