What Causes High Crankcase Pressure In A Diesel Engine?

Every engine has some level of blowby, but the issue is magnified when it comes to huge diesels. Excessive blowby is the result of a big cylinder bore, high cylinder pressure from turbocharging, long hours of operation, and poor maintenance.

Blowby is defined as the leakage of any combustion gases, air, or pressure into the engine’s crankcase. On a large diesel, around 60% of the blowby passes through the piston rings and into the crankcase. When the pressure differential in the cylinder bore is greater than the pressure in the oil pan, this occurs. As a result, blowby is greatest during the expansion (power) stroke of the engine and lowest during the compression stroke.

What will result in a high level of crankcase pressure?

The Positive Crankcase Ventilation (PCV) system’s duty is to suction out blow-by gases from the crankcase and recirculate them via the intake manifold so they can be consumed in the engine. When the engine produces more blow-by gases than the PCV system can handle, a growing surplus builds up in the crankcase, causing excess pressure and, eventually, oil leaks. When faced with increased internal crankcase pressure, even the best-sealed gaskets leak.

In a diesel engine, what creates crankcase pressure?

It happens when a valve blows or the oxygen level in the engine drops, allowing fuel or oil to leak into the crankcase. In comparison to other sources such as intakes, it is more typical when exhaust gas enters the crankcase through turbine rings in the crankcase. There will be a wide range of issues caused by air, fuel, and other causes contaminating the crankcase.

What can I do to reduce my crankcase pressure?

Venting a conventional V-8 engine isn’t difficult. Usually, all that’s required is a breather atop each valve cover. Of course, replacing one with a PCV valve to introduce some vacuum into the system and redistribute the unburned hydrocarbons back into the engine via the carburetor or throttle body results in a cleaner and more environmentally friendly alternative. Supercharged applications, on the other hand, can be finicky. When employing a standard push-in style breather, increased pressure in the crankcase might produce blow-by, coating that trick engine compartment in a fine mist of fuel-oil. Adding a PCV valve is an excellent idea until the engine is boosted, at which point the internal check valve is forced shut, leaving the valve useless. Instead of pulling new air into the breather and using the PCV valve to relieve the crankcase pressure, the internal pressure is vented out the breather, potentially leading in another greasy blow-by incident. When the engine is under load or at high rpm, pressure builds up quickly and needs to be alleviated the most.

What is a typical diesel engine crankcase pressure?

Most diesel engines have a maximum permitted crankcase pressure of 1.0″ H2O to 4.0″ H2O. For diesel engines, contaminated crankcase emissions can be a major issue.

Is it possible for too much oil to generate high crankcase pressure?

To understand why overfilling your engine oil is a bad idea, it’s helpful to start with some basic information.

Engines are made up of hundreds of finely constructed pieces that work together at high speeds and temperatures, all of which require oil for optimum lubrication and smooth operation. Oil is added to an engine’s crankcase via the “Oil” cap beneath the hood by you or your mechanic. When the engine is not operating, the oil sits in the oil pan. When you start the engine, the oil flows throughout it and passes through an oil filter, which filters out pollutants that could cause damage.

The level in the oil pan grows too high when too much oil is applied. This permits the crankshaft, a fast-moving lobed rod, to come into touch with the oil and aerate it. The end result is a foamy, frothy fluid that can’t lubricate the engine adequately. Consider it your engine’s method of converting cream to whipped cream. Nobody wants their engine to be lubricated with whipped cream.

The extra oil also causes excessive pressure inside your engine, which will try to escape through various gaskets and seals. If one or more of these fails, leaks will occur, requiring costly repairs.

Is it possible for turbo to cause crankcase pressure?

When a turbocharged engine is running, the intake manifold is under pressure for the majority of the time. The gas and oil bypassing the rings is still present, and the turbocharger’s pressure can raise crankcase pressures. When this happens, a more sophisticated PCV system is necessary.

Before the turbocharger, there is a vacuum. On some engines, the vacuum generated by the pistons moving downhill is larger than the vacuum generated by the pistons moving upward, although this is not always the case. When the turbo is spinning, vacuum is created. The vapors from the crankcase are usually injected into the engine just before the turbocharger. When the turbo isn’t producing enough vacuum, some turbocharged engines use a bypass valve to pump crankcase vapors into the intake manifold.

Turbochargers aren’t fond of consuming the oil present in crankcase fumes. Carbon deposits on the vanes and housing from the oil can cause a loss of boost.

Large oil separators are generally built inside the valve cover or on the side of the engine block in modern turbocharged engines. A simple check valve does not control the crankcase pressure. Both the crankcase and intake pressures are monitored electronically or mechanically. When the time is appropriate, the mechanism guides the vapors to either the turbo or the intake manifold.

High temperatures and combustion gases can damage plastic, flexible diaphragms, and seals in these next-generation PCV systems, causing them to fail.

If the system develops a leak, unmetered air may enter the intake. Misfires and lean codes can result as a result of this. If the turbocharger system fails, the pressure generated by the turbocharger may make its way into the crankcase. Oil leaks can occur as a result of the increased pressure. If the pressure is high enough, it can even impede flow from the turbocharger oil return line, decreasing the bearings’ lifespan.

Is it possible for a burst head gasket to cause crankcase pressure?

Compression will enter the oil system and pressurize the crankcase if the head gasket between the cylinder and an oil gallery fails. The lubrication of critical bearings, such as the crankshaft main bearings, will be compromised by hot compression gasses.

The piston will also be able to pull oil into the cylinder, where it will be burnt away during the combustion process. This will eventually cause a decline in engine oil levels, as well as blue smoke from burning oil in the exhaust.

Blowby, how do you cut down on diesel?

“FTC Decarbonizer is added to the diesel at each fill to prevent engine blow by, and then you simply drive the engine clean! The decarbonization procedure is delicate and gradual, but effective, cleaning turbos and DPFs in the process.”

To restore full cleanliness to the lower piston rings, most engines will need to be cleaned from the oil side as well. This entails flushing the engine with Flushing Oil Concentrate. It targets hard, baked-on deposits and engine sludge with detergents and, according to the producers, restores the engine “throughout “as new clean”

The longer you ignore blow-by, the more carbon builds up in your engine. Black smoke and oil soot levels are rising! The vehicle’s performance and fuel economy decline. Excess carbon on pistons can lead to premature wear. Carbon buildup in the ring grooves causes the majority of fractured piston rings. The chance of engine failure is considerably lowered by cleaning the engine and, more importantly, keeping it clean!

Engine blow by reduced

The images below are from a decade ago, when Caterpillar D11R dozers were working in Queensland’s Bowen Basin. The rebuild life was estimated to be around 11,000 hours. Many failures occurred as a result of excessive carbon buildup, with some failures occurring after only 3000-4000 hours. Rebuild intervals were typically 8,000-10,000 hours. FTC Decarbonizer was used by one 10-piece fleet that stood out! At 15,000 hours, the first engine was pulled down and determined to be in great condition. They eventually settled on 18,000-hour rebuild intervals.

Turbochargers, EGR valves, and diesel particulate filters are all clogged by increased exhaust soot. Turbo seals are chewed away by increased oil soot. Blowby is responsible for a lot of disastrous failures.

Engine blow by difficulties can be resolved, resulting in engines that are less stressed, more efficient, and last longer. The key to extending the life of Euro V emission-controlled engines is to burn the fuel cleanly for low exhaust soot and low oil soot levels.

How can you tell if the crankcase pressure is too high?

Not only can you monitor crankcase pressure with a vacuum gauge or manometer, but you can also use a scope and an accurate pressure transducer like the Pico WPS500.

How much pressure should be in the crankcase?

What is the definition of crankcase pressure? Simply said, it’s the pressure in your engine’s crankcase that is higher than atmospheric (or positive pressure). You might measure the amount of crankcase pressure created in your engine by placing a pressure sensor or a pressure gauge on the crankcase. We installed a pressure sensor to our dyno to detect crankcase pressure on each car we dyno test, thanks to David Buschur’s suggestion. When the engine is in normal running condition, we commonly measure peak crankcase pressures on the range of 2.5 to 6.0 psi on engines employing the factory specified crankcase ventilation system (a PCV or “positive crankcase ventilation” system).