Blow By on a Diesel Engine: Cause, Symptoms & Solutions

Power and durability are what make diesel engines so popular. But they too can create problems. One of the common issues among diesel engines is blow-by. If you don’t have this fixed in time, it can cause some severe damage!

In some cases, combustion gasses escape the combustion chamber and find their way to the crankcase of the engine. This process is what is called blow-by. Blow by on a diesel engine can be the reason for several low performances. It can also trigger higher consumption of engine oil and various other damages.

How does it affect your diesel engine? Continue reading to learn about this and more about how to identify and repair it before it becomes more destructive.

What is Blow By on a Diesel Engine?

Combustion gasses in a cylinder slipping past the piston rings and entering into the crankcase is the process that the term “blow by” refers to. Normally, tight piston ring seals prevent them from escaping out of cylinder walls. Damage causes the seals to weaken and the rest is history.

Blow by on a diesel engine can end up mixing engine oil and other fluids. Naturally, poor performance would result. This is more common in older engines with higher mileage.

Symptoms of Blow By on a Diesel Engine

Here are some symptoms of blow-by on a diesel engine:

1. Excessive Smoke
   The common symptom of blow-by on a diesel engine is a lot of smoke coming out of your exhaust and crankcase. This happens because of the combustion gasses coming out of cylinder walls.
2. Loss of Engine Power
   If your diesel engine is experiencing blow by, you’ll clearly notice the loss in engine power. Blow by on a diesel engine can reduce your engine’s performance and efficiency.
3. Higher Engine Oil Consumption
   Forces of blow by engine oil to be extruded out of the crankcase, this increases the consumption of the engine oil. When you find that the level of your engine oil has decreased then that might be due to blow by on a diesel engine.
4. Pressure Build-Up in the Crankcase
   Pressure building in the crankcase is a tell-tale sign of blow-by. After this stage, oil will start to seep from the seals and gaskets.
5. Rough Engine Idle
   The excessive gasses coming out of the cylinder walls can disturb the normal engine cycle. This results in a rough idle or vibration in the diesel engine.

Major Causes of a Blow-By on a Diesel Engine

Check out the list below for the most common causes of blow-by on a diesel engine:

1. Damaged Cylinder Walls
   Damaged or stretched cylinder walls won’t achieve the tight seal that is needed. This means combustion gasses will leak and cause the blow-by.
2. Worn Piston Rings
   Time alone will cause the piston rings to wear down. This is especially true for engines that are poorly maintained.
3. Overheating
   The engines that have improper maintenance show frequent overheating. Overheating can cause serious damage to the inner workings of a diesel engine. This damage includes (but is by far not limited to!) piston rings.
4. Poor Engine Maintenance
   Various engine damages are experienced on the engines that don’t undergo regular oil and filter replacements. Without regular engine maintenance, piston rings and other components in diesel engines will be subjected to fast wearing out. This leads to blow by on a diesel engine.
   How to Diagnose Blow By on a Diesel Engine
   Diagnosing blow by on a diesel engine is very simple. Here are some steps you can take to diagnose blow by on a diesel engine:
5. Check for smoke
   Turn the key to crank the engine. Let it run for a few minutes. Check after a few minutes the crankcase breather or oil filler cap. If smoke is coming out of it, that is a sure indication of a blow by on a diesel engine.
6. Perform a Compression Test
   You can perform a compression to diagnose blow by on a diesel engine. The compression test shows the pressure inside the cylinders. If the compression is small, this means that the piston rings are sealing poorly. This would indicate that there is blow by on a diesel engine.
7. Monitor Engine Oil Consumption
   Monitor the consumption of engine oil. If you notice an increase in the consumption of engine oil, it might be a blow by on a diesel engine.
8. Pressure Test
   To make sure things check out, perform a pressure test on the crankcase! A higher pressure in the crankcase points to a gas leakage in the piston rings.

How to Fix Blow By on a Diesel Engine

If a blow-by on a diesel engine has been diagnosed, the next step is to fix it ASAP! Here are some common solutions:

1. Replace Ring Pistons
   Believe it or not, some blow-by can be fixed simply by replacing these worn piston rings! This being done by a professional mechanic is best. We advise choosing a professional since the repair process requires the engine to be disassembled. Give us a call to learn more about our pro services here at Superior Truck Trailer Repair!
2. Repair or Replace the Cylinder Walls
   If damaged cylinder walls are to blame for the problem, we advise you to repair or replace them to correct it!
3. Perform Regular Maintenance
   Once you have fixed your diesel engine, keep up with regular maintenance to prevent blow-by on a diesel engine in the future. Regular maintenance includes oil and filter replacements.
   

Choose Superior Truck Trailer for Diesel Engine Repair

Blow by on a diesel engine is a serious issue leading to the damage of various engine components. Blowby requires professional attention to get fixed. Our expert team at Superior Truck & Trailer Repair offers extensive diesel engine repair services. We have years of experience diagnosing and fixing the issues that keep your trucks down, like blow-by.

Whether you need piston ring replacements, cylinder wall repair or replacements, or regular maintenance, Superior Truck & Trailer is the best choice. Don’t let blow by damage your engine. Trust Superior Truck & Trailer to keep your diesel vehicle running smoothly.

Feel free to call us at (502) 789-6644 or visit our website to schedule your appointment.

FAQs

How can I keep my engine safe from blow-by?
Regular checks and maintenance can keep your engine safe from blow-by. Keep your diesel engine away from overheating and excessive load.

Can blowing by on a diesel engine cause engine failure?
Yes, if not fixed as soon as possible, it can damage various other engine components.

Can I fix the blow-by without replacing parts?
In very few cases you can get it fixed using engine restorer additives. However, for severe blow-by on a diesel engine, replacing the piston rings or cylinder walls can be the only solution.