A cracked engine block is bad news—in the world of automotive repair, it’s one of the most serious (and costly) problems you might encounter.
Sometimes, the issue is mistaken for a blown head gasket or cracked cylinder head because it can present many of the same symptoms.
But unfortunately, a cracked block is far worse than either of those problems, as it usually means your car needs a new engine.
What is an Engine block?
An engine block – also known as a cylinder block – contains all of the major components where the combustion process takes place in a reciprocating engine.
Usually made from an aluminum alloy (cast iron in older engines), it houses the cylinders and their components, the water cooling system and the crankcase.
Its metal construction gives it strength and the ability to transmit heat from the combustion processes to the integral cooling system in an efficient manner.
This water jacket, as it’s sometimes known, is supplied by the car’s radiator, which cools the water before it is pumped back into the engine block.
Without cooling, the engine quickly becomes less efficient and would ultimately seize.
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 (it secures to the engine block), together with the camshaft, 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. This reservoir provides lubrication for the engine’s moving parts and its level is checked electronically, via the car’s dashboard, or with the use of a dipstick, which is installed in the engine block.
The engine oil should be changed at prescribed intervals – this is done via the sump plus, which sits on the base of the block, or by using a vacuum pump and a hose inserted through the dipstick hole. The oil filter should be changed at the same time.
Components of an Engine Block
The main structure of an engine typically consists of cylinders, coolant passages, oil galleries, a crankcase, and cylinder head(s).
#1. Cylinder blocks.
A cylinder block is a structure that contains the cylinder, plus any cylinder sleeves and coolant passages. In the earliest decades of internal combustion engine development, cylinders were usually cast individually. Cylinder blocks were usually produced individually for each cylinder.
Following that, engines began to combine two or three cylinders into a single-cylinder block, with an engine combining several of these cylinder blocks combined.
In early engines with multiple cylinder banks such as a V6, V8, or flat-6 engine each bank was typically a separate cylinder block (or multiple blocks per bank).
Since the 1930s, mass production methods have developed to allow both banks of cylinders to be integrated into the same cylinder block.
Related: What is Internal Combustion Engine?
#2. Cylinder liners.
Wet liner cylinder blocks use cylinder walls that are entirely removable, which fit into the block by means of special gaskets. They are referred to as “wet liners” because their outer sides come in direct contact with the engine’s coolant. In other words, the liner is the entire wall, rather than being merely a sleeve.
Advantages of wet liners are a lower mass, a reduced space requirement, and that the coolant liquid is heated faster from a cold start, which reduces start-up fuel consumption and provides heating for the car cabin sooner.
Dry liner cylinder blocks use either the block’s material or a discrete liner inserted into the block to form the backbone of the cylinder wall. Additional sleeves are inserted within, which remain “dry” on their outside, surrounded by the block’s material.
For either wet or dry liner designs, the liners (or sleeves) can be replaced, potentially allowing overhaul or rebuild without replacement of the block itself, although that is often not a practical repair option.
Related: What is Cylinder Liner?- Function and Types
#3. 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 measure the power and size of an engine.
#4. Oil Passages or Galleries.
These allow oil to reach the cylinder head and the crankshaft.
#5. Deck.
This is the top surface of the block where the head of the cylinder sits.
#6. 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.
How to Tell if I Have a Cracked Engine Block?
- Poor engine performance caused by low engine compression;
- Visible engine smoke;
- Engine overheating caused by leaking antifreeze;
- Discoloration in a car’s oil or antifreeze;
- Leaking oil or coolant;
- Frozen coolant in the radiator;
- Excessive smoke from the exhaust; and
- Low levels of coolant.
Cracked engine blocks can be repaired, but usually require replacement, either with a rebuilt engine, a new engine, or a salvage engine.
Common Signs of a Cracked Engine Block
A cracked engine block is rather uncommon. Usually, the cylinder head(s) crack and start causing problems long before the block does. Still, there are instances where a block can crack, resulting in one or more of the following symptoms.
Note: Because other problems can present the same symptoms as a cracked block, you’ll want to perform a thorough diagnosis of the vehicle before performing any repairs.
White Smoke (Steam) From the Exhaust Pipe
There are coolant passages that run through the engine block. A crack in the block can allow coolant from those passages to leak into one of the engine’s cylinders, where the coolant is then burned during the combustion process.
As a result, you’ll see white smoke, which is actually steam, coming out of the vehicle’s tailpipe. You might also notice that the exhaust fumes have a sweet smell.
Coolant or Oil Leaks
A cracked engine block can result in an internal or external coolant leak. An external engine oil leak is also possible, depending on the location of the crack.
Engine Overheating
A cracked engine block can result in a coolant leak (either internal or external) that prevents the coolant from properly circulating through the engine. The engine can start to overheat as a result.
Rough Running and Misfiring
In some cases, a cracked engine block can result in a loss of compression that causes the engine to run rough and misfire.
Combustion Gases In the Cooling System
A cracked engine block can allow combustion gases to enter the cooling system. As a result, you might see an excessive amount of bubbles in the coolant before it begins to boil. You might also notice that the cooling system is under extreme pressure.
Coolant-Oil Intermix
It’s possible for a crack to develop between the block’s oil and coolant passages, resulting in a coolant-oil intermix.
Illuminated Warning Lights
A cracked block can trigger the check engine light, low coolant level light, and the engine over-temperature light. If your car is equipped with a temperature gauge, you’ll also see it begin to climb.
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.