What is an Engine block?
An engine block is a structure that contains the cylinders, and other parts, of an internal combustion engine. In an early automotive engine, the engine block consisted of just the cylinder block, to which a separate crankcase was attached.
Modern engine blocks typically have the crankcase integrated with the cylinder block as a single component. Engine blocks often also include elements such as coolant passages and oil galleries.
The term “cylinder block” is often used interchangeably with the engine block, although technically the block of a modern engine (i.e., multiple cylinders in a single component) would be classified as a monobloc. Another common term for an engine block is simply “block”.
Importance of Engine Block
An engine block contains the main components of an internal engine. It houses the water-cooling system, crankcase, and cylinders and their components. The use of metal in its construction gives it strength and the ability to efficiently transfer heat from the combustion process to the main cooling system.
The engine block is important in the functioning of the car by supporting components of the engine. It transfers heat from friction to the coolant and atmosphere and supports the lubrication circuit and auxiliary devices such as the alternator.
Its significance brings the need for drivers to regularly maintain their vehicles to prevent destruction to internal parts. Damage to parts of the engine can be caused by insufficient oil and overheating.
Regular inspection and maintenance of the engine block help in ensuring the car engine operate normally and efficiently. Maintenance is crucial to the block’s lifespan and to maintain optimal performance and economical usage of fuel.
How do engine blocks work?
The block was originally just a block of metal holding the cylinder bores, the water cooling jacket, oil passages, and the crankcase. This water jacket, as it’s sometimes known, is an empty system of passages, circulating coolant in the engine block. The water jacket surrounds the engine’s cylinders, of which there are usually four, six, or eight and which contain the pistons.
When the cylinder head is in place secured to the top of the engine block, the pistons move up and down within the cylinders and turn the crankshaft, which ultimately drives the wheels. The oil pan sits at the base of the engine block, providing a reservoir of oil for the oil pump to pull from and supply the oil passages and moving parts.
Air-cooled motors, like the old VW flat-four, and the original Porsche 911 sports car motor, don’t really have an engine block. Much like a motorcycle motor, the crankshaft spins in engine cases, bolted together. Bolted to these are separate finned cylinder “jugs”, which the pistons go up and down in.
Components of an Engine Block
- Cylinders. These are the spaces where pistons travel. They are large in size and have precisely formed holes to create a seal with the piston. The size and number of cylinders measures the power and size of an engine.
- Oil Passages or Galleries. These allow oil to reach the cylinder head and the crankshaft.
- Deck. This is the top surface of the block where the head of the cylinder sits.
- Crankcase. This houses the crankshaft and is found at the bottom of modern engine blocks.
Other components include engine mounts, core plugs, coolant, ancillary mountings, and faults.
Common problems with engine blocks
Being a big, precision machined, a hunk of metal, the engine block is designed to last the lifetime of the car. But sometimes things do go wrong. These are the most common engine block failures:
1. External engine coolant leak
The block can crack and begin leaking, or a freeze-out plug could work its way loose or rust out. Freeze-out plugs can be easily replaced, but cracks are usually terminal.
2. Worn/cracked cylinder
Eventually, after hundreds of thousands of miles, the smooth machined walls of the cylinders will wear to a point where the piston rings can’t seal against them well. On rare occasions, the cylinder wall can develop a crack, which will quickly result in a motor needing a rebuild.
Worn cylinders can be bored larger, for oversized pistons, and in extreme cases (or in aluminum blocks) iron sleeves can be inserted to make the cylinder walls perfect once again.
3. Porous engine block
Caused by contaminants that got into the metal during the manufacturing process, voids in the casting often cause no issues at all for a long time. Eventually, a poorly cast block can start to seep and leak, either oil or coolant, from the area where the imperfections are.
There’s nothing you can do about a porous engine block because it’ll have been faulty from the day it was molded. Having said that, any leaks that may arise from a porous block should be minor and if they surface within the manufacturer’s warranty period the engine should be replaced free of charge.
5 Symptoms of Engine Block Failure
A cracked engine block can cause a range of problems. Ultimately, since the circulation system that cools the engine is comparatively fragile, a cracked engine block will lead to coolant leaking out of the area it is needed and leaving the engine to overheat. If left untreated, this will lead to engine failure and may result in the vehicle having to be written off. A cracked engine block can result in:
- Oil and antifreeze mixing
- Engine overheating
- Low engine compression
- Excessive engine smoke
- Visible crack in block
How Much Will Engine Block Repair Cost at a Garage?
A failure in the engine block will leave you stranded and more often than not facing a huge repair bill (at least $1,200, probably more).
The cost of repairing a cracked engine block can vary considerably depending on the garage you visit, the severity of the crack, and the car you drive.
The technique used to repair the crack can also affect the total and you may have to weigh up the sense in repairing it when it may be more cost-effective to buy a new engine or even a new car.