Engine Crankshaft: Everything you need to know

The engine block  is composed by the camshaft, cylinders, pistons and some other valves and complex parts . Of all the moving parts within the engine block, the most important is undoubtedly the crankshaft

In this article we explain how important the crankshaft is , what problems it might face  and what other components it influences. Continue reading the article.

What is the engine crankshaft?

The crankshaft is a metal component that is placed at the engine bottom. Made of aluminum, it is the component that suffers the highest load during the normal engine operation and is responsible for coordinating the cylinders operation.

The engine’s crankshaft transforms the linear cylinders movement into a rotational motion. These movements are made at high speeds so the crankshaft is subjected to high pressures. To resist to this pressure, the crankshaft  is made at high temperatures to ensure above average resistance.

What parts compose a crankshaft?

  1. Crankpin
  2. Main journals
  3. Crank web
  4. Counterweights
  5. Thrust washers
  6. Oil passage and oil seals
  7. Flywheel mounting flange



  • Crank Pin

The crankpin is a mechanical part of an engine. Which allows the connecting rod to be attached to the crankshaft very firmly.

The surface of the crankpin is cylindrical, to give the rotative force to the large end of the connecting rod. These are also known as connecting rod journals.

  • Main Journals

Journals have attached to the engine block. These bearings hold the crankshaft and provide it to rotate inside the engine block. This bearing is such as a plain bearing or journal bearings. The main bearings vary from engine to engine, often according to the forces given by the engine.

  • Crank Web

The Crank web is the most essential part of the crankshaft. Crank web connects the crankshaft to the main bearing journals.

  • Counterweights

The counterweights are a type of weight, that applies opposite force, which provides balance and stability to the crankshaft. These are mounted on the crank web.

They can eliminate the reaction caused by rotation. And it is very helpful for achieving the higher RPM and makes the engine run easily.

  • Thrust Washers

At some points, two or more thrust washers are provided to stop the crankshaft from moving lengthways. These thrust washers assemble among the machined surfaces in the web and the crankshaft saddle.

With the help of thrust washers, it can be easily maintained the gap and helps to reduce the lateral movement of the crankshaft. In many engines, these are made as part of the main bearings, usually, older types, use separate washers.

  • Oil Passage and Oil Seals

Crankshaft oil passage passes oil from main bearing journals to the big end journals. Normally the hole is drilled on the crank web. When the crankpin is in an upward position and combustion forces push the connecting rod to a downward position, it allows oil to enter between journal and bearing.

The crankshaft has some extend beyond the crankcase on both ends. This causes oil to leak from these ends. So, preventing oil from these openings, oil seals are provided. There are two main oil seals are connected at the front end and rear end.

  • Flywheel Mounting Flange

In most cases, the crankshaft attaches to the flywheel through the flanges. The diameter of the crankshaft wheel end is larger than the other end. This gives a flange face to mount the flywheel.



Damaged Crankshaft: 4 Sins

1. Engine Vibrations

One of the most common symptoms of a crankshaft problem is when the vehicle engine begins to vibrate more than normal. This vibration may indicate a broken crankshaft. If you are facing this symptom we strongly recommend to visit your mechanic.


2. Slow Throttle Response

When the crankshaft sensor isn´t correctly working, it cannot send the correct information to the engine central unit. This means that there will be a lag between the acceleration process and revs targeting.


3. Irregular start-up

When you start your vehicle and this one has an uncertain startup it might be a crankshaft problem. These cases are common on high millage vehicles.


4. Ignition Failure

When you are starting the vehicle and the  crankshaft  sensor notes any serious problems, it will not let the ignition to start.

What cares should be taken with the engine crankshaft ?

  • Use the engine oil according to the specifications recommended by the manufacturer.
  • Use the appropriate oil amount.
  • Avoid engine oil contamination with fuel or antifreeze;
  • Check lubrication system failures.

What’s the price of an engine crankshaft?

A crankshaft can cost around 300 euros. We remind you that this is a engine component and to  replace or repair it you will spend some more money, as the mechanic will have to lift the vehicle  to remove the engine and need a crankshaft lock key  to be able to repair or replace it.

Crankshaft Pulley

The crankshaft  pulley is located outside of the engine block  but connected to the camo on its front end.

The crankshaft  pulley transmits power to other engine components, such as the air conditioning compressor  and steering pump. As a secondary function, it also reduce vibrations in the camo.

This works as a bimass steering wheel, as it has inside damper elements that help to reduce the mentioned vibrations.

Crankshaft Sensor

The crankshaft  sensor indicates the position, wear and rotation speed of it. This sensor is in permanent communication with the engine control unit so that you can, if necessary, make revs adjustments

For its maintenance, it is advisable to check its condition every 60,000 kilometres and replace it every 120,000 kilometres.

Knowing now how important this component is in the vehicle operation, you should take proper cares to preserve and maintain your car crankshaft.

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