One of the engine problems you cannot afford to ignore is excessive engine blow-by. This is not to say you should ignore other car engine problems. However, engine blow-by can damage your engine extensively, requiring expensive repairs and replacements.
It also causes a trickle-down effect that damages other components of your car. Which potentially makes it the most expensive car repair job. Keep reading to learn how to fix blow-by on a diesel engine.
What causes blow-by in an engine?
Here are the main causes of engine blow-by causes;
Engine manufacturing defects
A variety of factors cause blow-by during the engine manufacturing process. Poor machined surfaces, incorrect piston-to-cylinder clearances, and poor quality control can lead to blow-by. For example, one installation or manufacturing can occur if the piston rings are not properly installed. This can cause the rings to leak, allowing oil and other fluids to enter the combustion chamber.
Another way is if the valve seals are not properly installed, which can cause oil and other fluids to enter the combustion chamber. Also, if there are any cracks or holes in the engine block itself, this can cause a blow-by. These manufacturing defects can ultimately lead to increased engine wear, reduced performance, and engine failure.
Damaged cylinder walls
The cylinder walls in an engine are subject to a lot of wear and tear. If the cylinder walls become damaged, it can also cause the engine blow-by. The most common way cylinder walls become damaged is by wear and tear. Over time, the friction between the piston and the cylinder wall wears down the material of both surfaces.
As the engine burns fuel, the piston moves up and down inside the cylinder. Over time, this can cause the cylinder walls to wear away and become eroded. This process is accelerated by high temperatures and pressures and debris and contaminants in the engine oil. Eventually, the cylinder wall becomes thin and weak and starts to develop cracks.
In addition, if the engine overheats frequently, this can also cause the cylinder walls to become damaged. Another way that cylinder walls can become damaged is from corrosion. This is most commonly seen in engines that have been sitting for long periods without being used. The acids in engine coolant can eat away at the metal of the cylinder walls, causing them to become thin and weak.
With time, the pistons’ continuous movement will lead to damaged or cylinder walls. It can also come from damaged pistons or piston rings. Last but not least, cylinder walls can be damaged by impact. This can happen if a piece of debris gets into the engine. Or if the engine suffers a sudden shock (such as from a car accident).
When the cylinder wall is hit, it can develop cracks or even shatter. You can often notice damaged cylinder walls by listening for piston slaps. Worn-out cylinder walls are not very common, luckily. If it happens, you either need to bore the cylinders to a bigger size and replace the pistons or replace the engine block.
Worn out the piston and piston rings
There are several reasons engine blow-by can occur, but the most common cause is worn-out piston rings or pistons. When these parts wear out, oil and other fluids leak past them and into the combustion chamber. This can cause a build-up of pressure in the chamber, eventually leading to the engine blow-by.
The piston rings in an engine are responsible for sealing the gap between the piston and the cylinder wall. However, these rings can become worn out over time and no longer seal the gap as effectively. When this happens, the gasses produced during combustion can escape into the crankcase.
Pistons are vital for moving the crankshaft. When the pistons start wearing out, they become smaller, while the cylinder walls become larger. Pistons are mostly made from aluminum – which happens to be a soft metal – when it wears out; it creates grooves in the piston while deposit accumulation occurs on the cylinder walls.
The fuel-air mixture soon finds its way into the crankcase. It can also be due to holes in the pistons from a knocking engine. The piston rings are continuously being pushed back and forth in the cylinder wall, and with time they become worn and destroyed. This leads to leakage of gases, which causes blow-by.
Sometimes the piston rings can get stuck, which will often be solved by pouring some diesel into the cylinder and letting it sit for a while. Then, with a little luck, they will come loose and seal against the cylinder wall again.
Faulty Crankcase ventilation
The crankcase in an engine is vented to allow the build-up of pressure to be released. However, if the ventilation system is not working properly, the pressure can build up and cause the engine to blow-by.
In some cases, you can mistake blocked crankcase ventilation for blow-by. The crankcase ventilation job is to recycle blow-by into the intake again. If the crankcase ventilation hoses are blocked, it will push it out from the oil cap once you open it, and you may think that your engine has a lot of blow-by.
Bad Valve Seals
Valve seals are responsible for sealing the gap between the valves and the cylinder head. Over time, these seals can become worn out and no longer seal the gap effectively. When this happens, the gasses produced during combustion can escape into the crankcase.
Bad valve guide seals or valve stem seals may cause a lot of trouble in the long run. They can damage your engine and also cause burnt valves. In addition, if your valves reach the point when they start bringing, you will pay a lot of extras to fix this problem.
If you have bad valve seals, the oil will travel down into the cylinders, burn with the fuel, and cause carbon build-up on the spark plugs and valves. If left untreated, it may jeopardize the valve sealing capability, cause you to lose compression, and burn a lot of oil in the process.
Worn valve stem seals will cause excessive oil consumption because the oil will be sucked past the seals and down through the intake valve guided by the vacuum. This leads to blue smoke from the exhaust or fouled spark plugs.
Damaged inlet valve seals will allow the valve train oil to be sucked into the intake and burned, so black smoke at the exhaust. And damaged exhaust valves will lead to all sorts of problems, including oil leaks.
Carbon Build Up
As an engine burns fuel, it produces carbon deposits. Over time, these deposits can build up and cause the piston rings and valve seals to seize up and function less effectively. When this happens, the gasses produced during combustion can escape into the crankcase.
Hard carbon deposits are a result of engine combustion. Over time these deposits progressively accumulate throughout several parts of the engine, including cylinder walls, piston ring grooves, valves, diesel injectors, diesel particulate filters, turbochargers, etc.
Hard carbon virtually cements piston rings in their grooves, restricting their ability to seal effectively against the cylinder walls. Also, hard carbon builds up in the cylinder cross hatch, giving the cylinders a highly polished surface. These conditions reduce cylinder compression and oil control, resulting in engine blow-by.
What is a normal blow-by?
Engine oil blow-by is when a mixture of air and fuel or combustion gases leaks between the engine’s pistons and cylinder wall into the crankcase. Engine blow-by can occur within both diesel and gas engines.
All engines have minor levels of blow-by, as piston rings aren’t completely watertight, even in new engines. For instance, a 12-liter engine in good condition may experience 1.5 cubic feet per minute (cfm) of blow-by under normal operating temperatures. That number increases to 3.5 cfm under colder temperatures.
Blowby happens when the internal combustion chamber of your engine forces contaminants such as air, fuel, and moisture past the piston rings and into the crankcase. If your engine’s piston rings don’t have a good fit or aren’t well-sealed, they cannot contain the pressure produced from the combustion and will instead leak air-fuel mixture and contaminants.
Over time, as the engine’s pistons move up and down against the cylinders during normal engine operations, both parts wear away. The cylinders become wider, while the pistons become smaller. The piston rings also wear away, making them less capable of maintaining a firm seal. As all the parts continue to grind against each other, these issues become more exaggerated, and the amount of blow-by can increase.
When does blow-by become an issue?
Engine blow-by can decrease your engine’s overall efficiency and performance, resulting in costly and time-intensive repairs or causing irreparable damage. An engine experiencing an engine blow-by will also produce a much louder noise than normal and force polluting exhaust fumes out of the engine vents.
Blow-by inhibits overall engine performance due to a loss of compression. Diesel engines operate by compression ignition. They convert fuel to energy by pressuring the cylinder, creating heat, and igniting diesel fuel.
When the cylinder leaks, it can’t contain as much pressure, leading to misfiring and poor engine performance. Additionally, when gases expand and slip past the piston rings, they cannot effectively push the piston down to make the engine produce sufficient output during the power stroke, resulting in a drop in horsepower.
Blow-by also coats parts of the intake with oil and fuel. After wear and degradation of piston rings and cylinder walls, more air, fuel, and moisture can slip into the crankcase and damage the parts. It will also result in increased fuel consumption.
If components such as air, fuel, and moisture slip into the crankcase, they can contaminate and dilute the oil. In addition, any remnants of gases, unburned fuel, moisture, sulfur dioxide or soot particulates are left behind in your engine’s compression chamber. These contaminants may slip into the crankcase. And then seep into the engine and cause extensive damage.
What are the blow-by signs and symptoms?
Below are the main engine blow-by symptoms;
Blue smoke from the exhaust
Blue exhaust smoke is typically an indication of engine blow-by. When an engine experiences blow-by, it means combustion gases escape past the piston rings and into the crankcase.
This can cause a build-up of pressure within the crankcase, eventually leading to engine damage. If you see blue smoke coming from your car’s exhaust, it is important to have it checked out by a qualified mechanic as soon as possible.
Knocking noise from engine bay
Another symptom of engine blow-by is a knocking noise coming from the engine bay. This is caused by the build-up of pressure within the crankcase, which can eventually lead to engine damage. It’s quite normal to hear a knocking noise from around the valve cover area due to an engine blow-by. This is because when the piston moves up and down, it creates a vacuum that pulls air through the gaps in the piston rings. As the air is forced through these tiny spaces, it collides with the piston and causes a knocking noise.
Although there can be multiple reasons for the knocking noise from the engine, if you only hear it when the engine is under load or working hard, it’s most likely due to blow-by. On the other hand, if you hear knocking at idle, it could be due to a mechanical issue such as worn piston rings or damaged bearings. In either case, it’s best to get the vehicle checked out by a qualified mechanic to diagnose the root cause of the problem.
Increased fuel consumption
One of the most common symptoms of engine blow-by is increased fuel consumption. When an engine burns fuel, it produces energy that turns the crankshaft. However, due to blow-by, some of this energy is used to push combustion gases through the gap between the rings and the cylinder walls.
Whenever blow-by allows some gases from the combustion chamber to escape into the crankcase, output power to fuel consumption is decreased. Hence, the reduced fuel efficiency. Over time, these escaping gases can build up in the crankcase and cause problems. Perhaps most importantly, they can increase your fuel consumption.
Excessive oil leakages
If you notice oil leaks around the seals and gaskets of your engine, this is another symptom of blow-by. These leaks are usually the result of the increased pressure in the crankcase, which puts strain on the seals.
Under normal operations, the seals can contain the pressure within the crankcase. However, in the case of blow-by, the pressure increases, and since the seals are rated for certain pressure levels, they give in, allowing for leakages.
Milky fumes
When you open the oil filler cap or oil pan and see milky white fumes, it indicates water in the oil. This generally happens when there is condensation in the crankcase due to blow-by gases. The water vapor present in these gases (air-fuel mixture) can mix with the engine oil and form an emulsion. When this mixture gets hot, it turns into a white milky substance. If you see this substance on your dipstick or oil filler cap, it indicates that your car is suffering from an engine blow-by.
Loss of Power
Another symptom of engine blow-by is that you will notice your vehicle is underperforming. This is because, during internal combustion, the air fuel mixture combusts in explosion form, pushing the pistons down.
However, when these gasses escape into the crankcase, they are not available to push the pistons down. This results in a loss of power and can make your vehicle feel sluggish when accelerating.
Engine misfires
Another symptom of engine blow-by is engine misfires. The main reason is that the pressure from the blow-by can cause the spark plugs to become fouled or damaged.
If the spark plugs cannot function properly, the engine will misfire. In addition, the pressure from the blow-by can also damage the piston rings. When the piston rings are damaged, they will no longer be able to seal the combustion chamber correctly. This will also cause engine misfires.
Sooty substance on the engine head
If you see a black sooty substance on the engine head, it’s an indication of oil burning. This generally happens when there is too much blow-by happening in the engine. When there is too much blow-by, it means that the piston rings are not able to seal the combustion chamber correctly.
This will cause some engine oil to be drawn into the combustion chamber and burned along with the fuel. The sooty substance is just engine oil that has been burned. Seeing this on your engine indicates that you have a problem with an engine blow-by.
Poor engine performance
If your engine is not performing as well as it used to, it could be an engine blow-by. One of the most common ways an engine blow-by can cause poor vehicle performance is by causing the engine to run lean.
When an engine runs lean, there is not enough fuel being burned in the combustion chamber. This can lead to several problems, including decreased power. As a result of the blow-by, small amounts of gases and vapors escape past the piston rings and into the crankcase.
These vapors contain hydrocarbons and other pollutants that can negatively affect air quality and your vehicle’s performance. This can also cause deposits to build up on engine components. These deposits can restrict airflow and negatively affect engine performance.
Engine failure
One of the most serious consequences of engine blow-by is engine failure. When there is too much blow-by happening in an engine, it can cause the piston rings to break. If the piston rings break, it will cause the pistons to start moving up and down in the cylinders. This will cause a lot of damage to the engine and can eventually lead to engine failure.
How do you fix an engine blow-by?
Below are potential solutions for Fixing engine blow-by;
Flush your engine
If you have an engine blow-by, one potential solution is to flush oil concentrate through your engine. This is because the oil flush helps to clean out any build-up of contaminants that may be causing the problem.
Check this too: Signs and Symptoms of Bad Spark Plug Wires
Additionally, flushing oil concentrate can also help to clear any engine sludge. Finally, it is a fairly inexpensive procedure. You can find oil concentrate flush at most auto parts stores.
Replace worn-out piston rings
The best way to treat engine blow-by is to change the piston rings. If worn-out piston rings cause your engine blow-by, you will need to replace them. New piston rings will provide a tighter seal between the piston and cylinder wall and help prevent blow-by gases from escaping into the combustion chamber. This will help improve engine performance and efficiency and extend your engine’s life.
Notes: This involves taking the engine apart and replacing the piston rings. It is a fairly difficult job and should only be attempted by someone with experience.
Replacing piston rings is one of the toughest and most expensive problems. On average, you can expect to pay between $1,200 and $4,000 for the parts and labor. However, if you have a luxury vehicle, the cost could be closer to $5,000.
Replace Pistons
You may also want to scrutinize the pistons while you replace the piston rings. If you see any damage to the pistons, you may need to replace them. When you replace the pistons, you often want to resurface the engine block.
Change Valve Seals
Another way to treat engine blow-by is to change the valve seals. This involves taking the cylinder head off and replacing the valve seals. This isn’t as difficult as replacing the rings, but it can be challenging and requires skilled labor.
Change the Crankcase Ventilation Valve
You first need to check your crankcase ventilation to make sure it is clear of sludge and dirt. Try to remove a hose and blow through it to make sure it’s clear. Also, check the PCV valve.
If the Positive Crankcase Ventilation Valve (PCV) is clogged up, the best way is to change it. The PCV is responsible for venting the crankcase; if it’s not working properly, it can cause a crankcase blow-by.
Install a new engine block or Remanufacture Cylinders
If your cylinder walls have scratches and are worn, you may need to resurface them or bore bigger cylinders with bigger pistons. The other option is to replace the engine block instead.
In the case of damaged cylinder walls, you might need to get a new engine block, or if you are lucky, engine sleeves will come in handy. In some cases, reboring works but might be costly or ineffective, depending on the severity of the damage.
Oil Treatment
Sometimes, the piston rings get stuck and will not seal against the cylinder walls. If you are lucky, this can be solved by pouring some diesel into the cylinders and letting them sit for a day or two.
How to Prevent Engine Blow-by
Here are a few things that you can do to help prevent engine blow-by;
Follow the maintenance schedule
One of the best ways to prevent engine blow-by is to follow the maintenance schedule for your vehicle. This will ensure that all of the parts in your engine are kept clean and lubricated. It is also important to make sure that you change your oil regularly. Dirty oil can cause a build-up of deposits on engine components, which can eventually lead to a blow-by.
Another important part of following the maintenance schedule is checking your engine regularly for any signs of wear or damage. This way, you can catch any potential problems before they cause serious damage to your engine.
Ventilate your crankcase
Another way to prevent engine blow-by is to ensure that your engine has proper crankcase ventilation. This ventilation system helps reinject blow-by gases into the combustion chamber, where they can be burned off.
If your engine does not have proper crankcase ventilation, blow-by gases will build up in the crankcase and eventually cause pressure to build up. This can lead to oil leaks, as well as engine damage.
Flush your engine with an oil concentrate regularly
Flushing an oil concentrate cleans the engine. The oil concentrate is usually mixed with hard-baked carbon. The mixture is run via the engine’s movable parts. It helps remove the engine sludge and effectively reduces blow-by and smoke, restores compression, and frees the piston rings.
Oil treatment
Oil treatment helps reduce blow-by. Like your vehicle’s engine ages, gaps are created in the movable parts. Combustion gases tend to leak from piston rings. This improves the engine’s performance.
While performing an oil treatment, you should avoid doing it if the engine is still hot. Also, ensure that the car is in parking gear and that the emergency brake is on. After you put the oil in the oil filter, start the engine and allow it to idle for a few minutes.
Use an FTC Decarbonizer
The Decarbonizer is also used to fix engine blow-by for diesel-driven vehicles. It is added into the diesel at every fill, and then you just drive the engine clean. The process of decarbonizing is quite gentle, progressive, and very efficient. It also cleans DPFs and turbos.
The more a blow-by is ignored, the more and more carbon accumulates in your engine. Excessive carbon leads to rapid wear. However, when you clean up the engine and maintain it that way, the risk of engine failure becomes almost insignificant!
Use High-Quality Fuel
A good way to prevent engine blow-by is to use high-quality fuel. This fuel will help to keep your engine clean and free of deposits. It will also help improve your engine’s performance and extend its life.