Engine blow-by, also known as unwanted gas leakage from a piston or sealing rings, can occur in a majority of diesel engines when pressure is maximized. It is primarily caused by piston rings leading to an engine using more fuel than normal.
Have you ever been driving down the road, only to end up behind a bus or semi truck that sounds as if it is roaring, spitting out huge exhaust clouds? This is caused by a common issue called engine blow-by, and it is a problem that may occur in your generator’s engine, too.
Engine blow-by is a serious issue that occurs when there is a leak consisting of an air-fuel mixture for combustion gases in between a piston and cylinder wall, leaking into the crankcase of an automobile or machine.
Typically, engine blow-by happens inside diesel engines, but is not uncommon in gas engines.
Your engine is a fine-tuned machine, and the smallest disruption can cause problems. Engine blow-by occurs when the internal combustion in your engine’s combustion chamber builds up, pushing out pollutants into the air, like fuel and moisture, past the piston rings in the crankcase. If the piston rings are not closely fitted, they cannot contain the pressure that is produced from the engine’s internal combustion, thus resulting in contaminants leaking into the air.
In a large diesel engine, about 60 percent of the blow-by passes through the piston rings and into the crankcase. This happens when the load differential between the oil pan and the cylinder bore is at its maximum. As a result, blow-by is maximum during the compression and expansion (power) strokes of the engine. The sources of the residual 40% of blow-by, which most people overlook, include the truck’s air brake compressor and turbocharger.
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What causes engine blow-by?
Nearly every part of an engine needs to be replaced and repaired from time to time, and piston rings are no different. After heavy use, piston rings will sustain damage and wear, resulting in an inability to maintain a close seal. Incomplete internal combustion leaves deposits on the piston rings, such as soot, sludge, or oil, furthering the ring’s inability to maintain a seal. Additionally, broken, ill-fitted pistons, even without heavy usage, do not allow for a proper seal. Without this close seal, contaminants from your engine can escape the crankcase and leak into the air.
This is why it is so important to ensure that the piston rings on your engine are properly fitted, without defects, and in good condition at all times.
How does engine blow by harm engines?
Blow-by severely lessens the effectiveness of an engine. Since it builds up in the crankcase, blow-by leaves parts of your engine coated with deposits, like oil and fuel, making it difficult to work properly. This is only furthered by aged piston rings, as their seal gets worse over time, allowing more air, moisture, and pollutants to escape or be trapped within the crankcase.
When these contaminants and gases go through the piston rings’ ineffective seal, they cannot push the pistons down and power the engine properly during the power stroke. This lessens the torque and horsepower of the engine, which is so important in powerful machines like generators.
How engine blow by is caused?
Engine blow-by is also a cause of increased fuel consumption. When blow-by allows pollutants to collect in the crankcase, they can debase and cause dilution in the oil. This means the oil will need to be changed more frequently, and due to the ineffective seal, likely the machine will need to be refueled more often, too. This is not an inexpensive feat. Additionally, blow-by can leave behind dangerous deposits in the compression chamber, like remnants of unburned fuel, sulfur dioxide, soot, and moisture. These contaminants can seep deeper into the engine, causing irreparable damage, which is extremely expensive to repair or replace.
Lastly, engines suffering from blow-by produce large amounts of exhaust fumes and can be extremely loud, making them unpleasant to be around and even environmentally unsafe. This is especially an issue if the machine will be around people, such as in a building, job site, or on the road.
How can you Test an Engine Blow-by?
There are a few ways to know how to test a blow-by in an engine.
- Blowing-by is marked by loud or sputtering noises originating from the engine, often accompanied by exhaust clouds or expelled fumes.
- White smoke arising from a valve cover or the oil-fill tube is one of the most noticeable indicators of severe blow-by.
- A layer of oil film surrounding the tube is another warning indication because blow-by contaminates the oil with unburned fuel and allows it to leak into the crankcase. It may indicate that a significant amount of gasoline or oil is seeping into the crankcase and producing blow-by if you notice that your generator is utilizing more fuel or oil than usual.
- Raised incomplete combustion, which results in soot trapped inside the cylinder walls, is a result of blow-by.
- If your generator is challenging to get going or continue running, blow-by could be the cause, as it interferes with critical engine functions.
How can you prevent engine blow by?
As Benjamin Franklin once said, “an ounce of prevention is worth a pound of cure”. This is especially true when it comes to your engine, as keeping it maintained is the most effective way to prevent engine blow-by. Stay up to date with oil changes, ensuring to check for buildup of solid carbon, which can erode metal, damaging your engine over time. There are treatments that can be added to your engine’s oil and fuel that can help break down these dangerous solids, making them easier to remove. Though it is more expensive, using top tier, high quality oils have been proven to prevent solid carbon buildup and help keep the engine in great shape for longer (as opposed to low quality oil and fuel). Additionally, you can send oil samples from your engine to be checked, where they can be examined for dangerous contaminants, helping you stay informed about the state of your engine.
My engine is actively suffering from engine blow by. What now?
Unfortunately, if your engine is already showing signs of blow-by, the damage has been done. While you can take steps to clean and replace parts of your engine, especially the piston rings and cylinder walls, this can be expensive and may be more than the engine is worth. It might be time to consider purchasing a new machine.
Is your generator showing signs of engine-blow by? At Swift Equipment Solutions, we are here to answer any questions you may have about purchasing a new generator or a used generator. Call us at +1-866-571-0044 or send us an e-mail at sales@swiftequipment.com today!
Frequently Asked Questions about engine blow by
Is engine blow by normal?
Unfortunately, engine blow-by is a common occurrence, especially with large machines, and even in a new engine, piston rings are not alway 100% effective. Though engine blow-by is not uncommon, it can be dangerous and should be dealt with as soon as possible.
Is engine blow by bad for your engine?
Yes! Blow-by can coat different parts of your engine with contaminants, making your engine more ineffective than it should be. It can severely lessen torque and horsepower in your engine, which is especially important in machines like generators, trucks, and buses.
What is the best way to prevent engine blow by?
The best way to prevent engine blow-by is through regular maintenance and observation. If you can replace piston rings and see problems within your oil before it becomes an issue, your engine (and your pocketbook) will thank you!
Why is my engine experiencing blow by?
This phenomenon is caused by an increase in fuel consumption by the engine. The blow-by results in allowing pollutants to collect in the crankcase. The pollutants debase and cause dilution of the oil.
Hence, the oil needs to be changed at shorter intervals, and the machine needs to be refueled often. This usually happens when piston rings are not fitted snuggly or when deposits collect on the piston rings, no longer allowing for a proper seal.
Is it expensive to repair damage caused by blow-by?
Yes, the blow-by leaves behind dangerous deposits in the compression chamber. These include moisture, soot, remnants of unburned fuel, and sulfur dioxide.
As the various contaminants can seep deeper into the engine, they can cause irreparable damage. The replacement and repair of the various engine parts come at a considerable cost. Hence, it is best to avoid blow by altogether.
Is it unsafe when engines experience blow by?
Well, the engine blow-by phenomenon is accompanied by two effects – large amounts of exhaust fumes are released. Secondly, the activity is accompanied by extremely loud, unpleasant sounds.
The fumes can also be harmful if it results in human exposure. The large sounds may alarm people and workers in the vicinity.
Can I repair the damage caused by the blow-by?
When your engine experiences a blow-by, a lot of damage has already been done. You can consider cleaning the engine. You can also consider replacing certain engine parts, such as piston rings and cylinder walls.
However, this is an expensive proposition, and there is no guarantee that it will be functioning smoothly again. The less risky and cost-effective option is to purchase a new, optimized engine and maintain it well to prevent blow-by from happening in the future.
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