How to Fix Blow by on a 7.3 Powerstroke

Blow by in a 7.3 Powerstroke diesel engine is a common issue that occurs when combustion gases escape past the piston rings and enter the crankcase, causing increased pressure and reducing engine efficiency. Fixing blow-by typically involves diagnosing the root cause and performing the necessary repairs.

Here are the Steps to Stop blow by on 7.3 Diesel:

1. Diagnosis:

a. Compression Test: Perform a compression test on all cylinders to determine if there is a significant drop in compression. Low compression can indicate worn piston rings, cylinder wall damage, or a faulty head gasket.

b. Leak-Down Test: Conduct a leak-down test to identify specific cylinder leakage. This will help pinpoint the source of the blow-by, such as worn valves, rings, or a cracked cylinder head.

c. Visual Inspection: Inspect the engine for oil leaks, damaged hoses, and other visible issues that might contribute to excessive blow-by.

2. Replace Worn Components:

a. Piston Rings: If the compression test reveals low compression, worn piston rings may be the cause. Replacing the piston rings involves removing the cylinder head and oil pan, which is a complex and labor-intensive task. It’s often best left to experienced mechanics.

b. Valve Seals: If the leak-down test indicates valve leakage, worn valve seals may be to blame. Replacing valve seals typically requires removing the cylinder head, which is another job for a professional.

c. Cylinder Head: If the cylinder head is cracked or damaged, it may need to be replaced or repaired by a professional engine machine shop.

3. Proper Maintenance:

a. Change Oil Regularly: Ensure that you are using the recommended oil grade and changing the oil and oil filter at the recommended intervals. Clean oil helps maintain proper lubrication and reduces the risk of blow-by.

b. Air Filter: Replace the air filter as recommended to ensure the engine receives a clean and adequate supply of air for combustion.

c. PCV (Positive Crankcase Ventilation) System: Check and clean the PCV system components, including the PCV valve, hoses, and breather, to ensure they are functioning properly.

d. Turbocharger Inspection: A malfunctioning or damaged turbocharger can contribute to blow-by. Inspect and service the turbocharger as needed.

4. Seek Professional Help:

If you are not experienced with engine repairs, it’s advisable to seek the assistance of a qualified diesel mechanic or a specialized Powerstroke technician. They have the tools, knowledge, and experience to diagnose and repair complex engine issues.

5. Preventative Maintenance:

After addressing the blow-by issue, make sure to continue with proper maintenance practices to prolong the life of your 7.3 Powerstroke engine.

Keep in mind that diagnosing and fixing blow-by in a diesel engine can be a complex and labor-intensive process. It’s crucial to accurately identify the root cause and address it effectively to avoid further damage to the engine. Regular maintenance and timely repairs are essential to keep your 7.3 Powerstroke running smoothly.

What Causes Excessive Blow by in a Diesel Engine?

Excessive blow-by in a diesel engine occurs when combustion gases, including exhaust gases, escape past the piston rings and enter the crankcase. This phenomenon is typically caused by one or more underlying issues, and addressing the root cause is essential to prevent engine damage and maintain performance.

Here are some common causes of excessive blow-by in a diesel engine:

Worn Piston Rings:

Over time, the piston rings can wear down, lose their sealing ability, and allow combustion gases to bypass them. This is one of the most common causes of blow-by.

Cylinder Wall Damage:

If the cylinder walls become scored, scratched, or otherwise damaged, the piston rings may not be able to create a proper seal, leading to blow-by.

Cylinder Head Problems:

  • Worn or Damaged Valves: Worn valve seals, valve guides, or valve seats can result in leaky valves, allowing exhaust gases to enter the crankcase.
  • Cracked Cylinder Head: A cracked or damaged cylinder head can also lead to blow-by by allowing gases to escape.

Faulty Head Gasket:

A damaged or blown head gasket can compromise the seal between the cylinder head and engine block, causing combustion gases to escape into the crankcase.

Turbocharger Issues:

A malfunctioning or damaged turbocharger can lead to excessive pressure in the intake or exhaust system, which can contribute to blow-by.


Diesel engines that overheat may experience damage to the piston rings, cylinder walls, and other internal components, leading to increased blow-by.

Incorrect Oil Viscosity or Contamination:

Using the wrong type of oil or oil with contaminants can affect the sealing properties of the piston rings, leading to blow-by.

High Engine Hours or Mileage:

As diesel engines age and accumulate mileage, wear and tear on various components, including the piston rings and cylinder walls, can increase the likelihood of blow-by.

Improper Maintenance:

Neglecting regular maintenance, such as failing to change the oil and oil filter at recommended intervals, can contribute to blow-by over time.

Poor Air Filtration:

A clogged or inefficient air filter can lead to inadequate combustion, incomplete combustion, and increased levels of blow-by.

PCV (Positive Crankcase Ventilation) System Issues:

Problems with the PCV system, such as a clogged PCV valve or breather, can disrupt the crankcase ventilation, contributing to blow-by.

Injector Problems:

Malfunctioning fuel injectors can affect combustion efficiency, leading to incomplete combustion and increased blow-by.

Addressing excessive blow-by typically requires a thorough diagnostic process to identify the specific cause of the issue. Depending on the root cause, repairs may range from relatively simple maintenance tasks to more complex engine overhauls.

It is essential to consult with a qualified diesel mechanic or technician to diagnose and address the problem correctly to prevent further damage to the engine. Regular maintenance and prompt repairs are key to preventing excessive blow-by and ensuring the longevity of a diesel engine.

How to Fix Blow-By in Engine?

Blowby in an engine occurs when combustion gases and other byproducts escape past the piston rings and into the crankcase. This can be a sign of internal engine wear or other issues. To fix blowby in an engine, you’ll need to identify the underlying problem and then take appropriate corrective actions.

Here are the steps you can follow:

1. Diagnosis:

  • Perform a compression test: This will help you determine if there is a problem with the piston rings or cylinder walls. Low compression in one or more cylinders can be a sign of blow by.
  • Check for excessive oil consumption: If your engine is burning oil, it can contribute to blow by. Monitor your oil levels to see if they are decreasing rapidly.

2. Replace the PCV (Positive Crankcase Ventilation) valve:

The PCV valve is responsible for maintaining proper crankcase ventilation. A malfunctioning PCV valve can lead to increased pressure in the crankcase and contribute to blowby. Replace it if it’s faulty.

3. Inspect and clean the PCV system:

Ensure that the PCV system is clean and free of clogs. This includes checking hoses and passages for obstructions or carbon buildup.

4. Use high-quality engine oil:

Switch to a high-quality engine oil that is designed for your engine’s specifications. The right oil can help reduce friction and wear on the piston rings and cylinder walls.

5. Regular maintenance:

Keep up with routine maintenance tasks, such as oil changes and air filter replacements, as recommended by your vehicle manufacturer. Maintaining your engine in good condition can help prevent blow by.

6. Address worn piston rings or cylinder walls:

If your compression test reveals low compression due to worn piston rings or cylinder walls, you may need to rebuild or replace the engine. This is a more extensive and costly repair, often requiring the assistance of a professional mechanic.

7. Check for other engine issues:

Sometimes, blow by can be a symptom of other engine problems, such as a damaged head gasket, worn valves, or a cracked cylinder head. Address any underlying issues to prevent further damage.

8. Seek professional help:

If you’re not confident in diagnosing or repairing engine issues yourself, or if the problem persists after attempting the above steps, it’s best to consult a qualified mechanic or engine specialist. They can perform a more thorough inspection and recommend the appropriate repairs.

Remember that addressing blow by in an engine may vary depending on the specific make and model of your vehicle. Always refer to your vehicle’s service manual for guidance and follow manufacturer-recommended maintenance schedules.

How Long Will an Engine Last with Blow-by?

The lifespan of an engine with blow-by can vary widely depending on several factors, including the severity of the blow-by, the engine’s design and construction, the type of fuel used, the level of maintenance it receives, and how the engine is operated. Here are some general considerations:

  1. Severity of Blow-By: The extent of blow-by is a critical factor. Minor blow-by may not significantly impact the engine’s longevity, while severe blow-by can accelerate wear and potentially lead to catastrophic engine failure.
  2. Engine Design: Some engines are more robust and better able to tolerate blow-by than others. Engines with higher-quality components, such as forged pistons and stronger cylinder walls, may last longer with blow-by.
  3. Maintenance: Regular maintenance can help manage the effects of blow-by. Timely oil changes, air filter replacements, and addressing issues promptly can extend an engine’s life.
  4. Fuel Quality: The type and quality of fuel used can affect engine longevity. Poor-quality fuel or fuel with contaminants can contribute to wear and damage.
  5. Engine Load and Operation: How an engine is used also matters. Engines subjected to heavy loads, high RPMs, or extended periods of high stress are more likely to experience accelerated wear and potentially shorter lifespans.
  6. Temperature and Environmental Conditions: Operating an engine in extreme temperatures or harsh environmental conditions can affect its lifespan. High heat, for example, can exacerbate wear and tear on engine components.
  7. Proper Repairs: If blow-by is diagnosed and repaired correctly, it can help extend the engine’s life. However, if the underlying issues causing blow-by are not addressed, the engine’s longevity will still be compromised.

In general, an engine with minor blow-by that is well-maintained and not subjected to extreme operating conditions might continue to function for a considerable amount of time. However, it’s important to note that blow-by is a symptom of underlying issues, and if left unaddressed, these issues can worsen over time, leading to more severe damage.

Engines with severe blow-by are at greater risk of suffering catastrophic failures, such as piston and cylinder wall damage or a damaged crankshaft, which can render the engine unusable.

Ultimately, there is no specific or fixed lifespan for an engine with blow-by. It depends on the factors mentioned above and how well the engine is cared for. If you suspect your engine has blow-by, it’s advisable to have it inspected and repaired by a qualified mechanic to prevent further damage and potentially extend its useful life.

How Much Blow by is Too Much

Too much blow-by in an internal combustion engine is typically considered a problem when it exceeds 5-10% of the engine’s total airflow, as it can indicate issues with piston rings or other components affecting engine efficiency and emissions.

Is Blow by Normal On a Diesel

Some level of blow-by is normal in diesel engines, as it’s a byproduct of the combustion process. However, excessive blow-by can still be a sign of problems such as worn piston rings, cylinder wear, or other issues that may require attention to maintain engine performance and emissions. Monitoring and addressing excessive blow-by is important for diesel engine maintenance.

How Much Blow by Is Normal 6.0 Powerstroke?

In a 6.0-liter Power Stroke diesel engine, a small amount of blow-by is normal, but it should be minimal. A typical guideline is that less than 5% of the total air volume should be blow-by. However, this is a general guideline, and the specific condition of the engine, maintenance history, and other factors can affect what is considered “normal.”

If you suspect excessive blow-by or have concerns about your engine’s performance, it’s advisable to have it inspected by a qualified mechanic to determine if any issues need to be addressed.

How Do You Know If Your 7.3 Has Blow-By?

If your 7.3 has blow-by, you will notice a decrease in performance and an increase in fuel consumption. You may also notice black smoke coming from the exhaust or oil leaking from the engine.