We’ve recently covered a range of key gas and diesel engine components in our Tip of the Week section. This week, we’ll cover one of the less “heralded” parts of an engine – the engine block.
If you were to ask, “Isn’t an engine block just a hunk of metal?”, I wouldn’t fault you. The short answer is “yes,” but to the trained eye, an engine block is much more.
I think you will be surprised at how complex these little hunks of metal are, and we will examine design, function, and maintenance best practices to ensure you get the most out of your machine.
Engine block fundamentals
An engine block is usually cast from iron or, increasingly, aluminum. Aluminum is much lighter and offers enhanced cooling properties. Regardless of the metal used, the block typically contains the crankcase and cylinders, but designs may include the camshaft journals and passages for oil (galleries) and coolant.
Depending on the block, cylinders may be cast into the unit, or the block may be designed to receive a cylinder liner insert. Cylinder inserts are defined as “wet” or “dry.” The wet inserts come into direct contact with the coolant, while “dry” inserts involve a dry liner surrounded by block material.
Other terms that you typically include long and/or short block. A long block assembly includes the cylinder head, while a short block considers the block below the head.
Cooling and lubrication
An engine block is either air- or liquid-cooled. Air-cooled blocks are cooled by heat exchanged with ambient air. This process may be aided by a fan.
In liquid-cooled engines, heat is transferred via passages cast into the block, allowing water to circulate though the block where heat is exchanged and the resultant hot water is cooled at the radiator.
Most liquid-cooled engines use a mixture of water and ethylene glycol (hereby referred to as glycol) to help cool an engine block. This is necessary as coolant mixtures have a boiling point well above engine operating temperature and contain inhibitors to prevent corrosion. The industry term for coolant is “antifreeze.”
The water to glycol ratio in coolants is typically 50/50, but the ratio truly depends upon ambient operating conditions around the engine. The glycol-to-water ratio selected will ensure maximum heat exchange and long block life.
The engine block also contains oil ports, often referred to as galleries, which allow oil under pressure to flow from the crankcase to the bearings, crankshaft, camshaft, and heads. The purpose of the oil is to help reduce friction, thereby lessening the overall heat of engine operation and wear. In addition, when the oil returns to the crankcase, air assisted heat exchange takes place, further enabling engine cooling.
Proper engine block maintenance
Engine blocks do not require much maintenance at all. They are typically maintenance-free until a problem occurs, and most issues are a result of coolant leaks.
If a coolant leak occurs, it’s critical to identify the source of the leak. Problems with the water pump, hoses or radiator can be easily repaired, but if the block is cracked, the engine will typically have to be replaced.
Occasionally, coolant will seep out of the core plug. These plugs can be replaced, but care must be exercised when pressing in a new plug.
A bad casting of a block may cause no issues for a long time, but as the engine reaches its service life of the engine, the defects may result in a crack, also resulting in a coolant leak. There is nothing to be done here other than replace the block. The good news? This type of failure is rare.
Block lubrication is simple, as it is accomplished by the engine oil contained within the crankcase. The oil is typically applied by bath, splash, and pressure methods.
To perform, the oil must contain stable base stocks and be fortified with additives that improve viscometrics, oxidation stability, and anti-wear performance. Synthetics are advantageous here, as their pumpability, stability, and film strength are ideal for the application.
I hope this tip helps you get the most out of your engine. If you have any questions, please leave a comment in the section below.
Dear Rick, what are the causes of a faulty engine block associated with high temperatures? I was told by an engineer; the block was very hot. Do you know what are the reasons? I will look forward for your response.
Jose - If an engine block is overheated it may crack. Most often the cause of overheating is lack of coolant flow.
Thanks for your response, Rick. I will let the customer know about this doubt you have regarding the reasons why the block gets overheated. Greetings.