Auto Anatomy: Connecting Rod in a Car Engine

  • Connecting Rod Function
  • Where It Is Located
  • Important Parts
  • Connecting Rod Types
  • Malfunctioning
  • Symptoms
  • FAQs

The efficient functioning of a car’s combustion engine depends on the reciprocating motion of the pistons. Pistons are connected to the engine and crankshaft via connecting rods. From transferring combustion pressure to sustaining engine power, connecting rods are vital in the overall process.

Let’s find out more about the working of the engine connecting rod, which makes it an essential performance part.

More About Connecting Rod Function

A connecting rod, shortened as a ‘con rod’, transmits force from the piston to the crankshaft. This important engine part plays a pivotal role in converting the reciprocating motion of the piston into rotational motion. The rapid activity subjects the connecting rod to alternating tensile and compressive forces during each engine cycle. 

As the piston moves upward during the compression stroke, the connecting rod experiences compression. Similarly, when the piston moves downward during the power stroke, the rod undergoes tension.

Connecting rods are typically made from high-strength automotive raw materials to withstand intense mechanical stresses. The precision and integrity of the connecting rod are critically maintained with proper lubrication by the right type of car engine oil. Proper lubrication is also essential to minimise friction and wear between the rod and the crankshaft.

Engine Connecting Rod Location

Location of connecting rod in engine
The important positioning of the component facilitates the piston’s reciprocating motion

The connecting rod is located within the engine block of an internal combustion engine. Each cylinder in an engine has a separate connecting rod and these rods are attached to a shared crankshaft. This positioning allows the connecting rod to play a critical role in converting the reciprocating motion of the piston. The compressed gases are then contained with the help of piston rings.

Important Connecting Rod Parts

The system of a connecting rod is relatively simple but crucial comprising the following parts:

Small End

The small end of the connecting rod is where the piston pin is housed. The piston pin allows the connecting rod to pivot and move with the piston. The movement is synchronised as the piston moves up and down within the cylinder.

Large End

The large end of the connecting rod attaches to the crankshaft. It often has a cap that is bolted or otherwise fastened to the rest of the rod. This cap is critical for maintaining the integrity of the connection. It also facilitates the assembly and disassembly during engine maintenance.

Bolts or Fasteners

Bolts or fasteners secure the cap to the body of the connecting rod. They are tightened to specific torque specifications to ensure a secure and reliable connection between the two parts. Properly sealed components and intact connections may also prevent problems like fuel dilution in engine oil. 

Rod Shank

It is the main, stretched-out part of the connecting rod, linking the small end to the large end attached to the crankshaft. A rod shank mainly comes in two shapes: H-beam and I-beam. An H-shaped cross-section shape provides a balance between strength and weight. Similarly, an I-beam connecting rod has a straight, I-shaped profile. It is also suitable for heavy-duty and high-torque applications


Bearings are usually inserted into the small or large ends of the connecting rod to facilitate smooth movement. The purpose of connecting rod bearing is also to reduce friction between the rod and the crankshaft or piston pin. The rotational energy produced from pistons is stored in a car engine’s flywheel.

The 4 Types of Connecting Rods

connecting rods are available in several types with difference in durability
Exploring the different types of engine connecting rods

Given the wide-ranging industry applications, there are four connecting rod types. Let’s list and detail each of the types.

Forged Steel Rod

Forged steel connecting rods are created through a forging process. It is a metal piece that is heated and shaped using compressive forces. This method produces strong and durable connecting rods suitable for high-performance engines. Forged steel rods are found in different types of sports cars and SUVs.

Cast Iron Rod

Cast iron connecting rods are often used in older or less performance-oriented engines. They are manufactured through a casting process, making them cost-effective but generally heavier than other types. Compact vehicles, such as sedans, hatchbacks or other car body types have cast iron connecting rods.

Billet Rod

A billet connecting rod is machined from a single piece of high-strength metal, such as aluminium or steel. The milling process enhances the rod’s structural integrity and allows for a more uniform composition.

Powdered Metal Connecting Rods

Powdered metal connecting rods are made by compressing metal powder into the desired shape. These engine rods have become quite famous in recent years. Powered metal rods are more cost-effective and high-performing than other conventionally used connecting rods. Such mechanical improvements are paving the way for the future of cars.

Connecting Rod Problems

Intense operations and pressure result in various mechanical problems
A host of problems entail rapid functioning

Timely diagnosing and fixing car engine problems is crucial to avoid any major breakdowns. Here’s what can potentially go wrong with a piston connecting rod. 

Bearing Wear

Bearings within the connecting rod may wear out due to friction and heat. Bearing wear or failure can also be caused by the improper lubrication of engine parts.

Bent Connecting Rods

High-stress conditions, such as engine over-revving, can cause connecting rods to bend. Bent rods affect the piston’s reciprocation movement. Such an engine connecting rod problem can result in performance issues. Moreover, to prevent any potential engine damage, keep an eye on the signs of failing piston rings.


Engine connecting rods can develop cracks, often due to engine operational fatigue or stress concentrations. Cracked rods compromise structural integrity and can lead to catastrophic engine failure if not addressed.

Piston Slap

Excessive clearance between the piston and connecting rod can result in a slapping noise during engine operation. It is due to the potential issue with the connecting rod’s fitting or structural wear.

Symptoms of Connecting Rod Failure

Know all the signs of bad connecting rods
Some common symptoms of failing connecting rod

Let’s walk through some of the common symptoms of connecting rod failure. 

Noticeable Knocking Sound

A distinct knocking or banging noise is a primary indicator of connecting rod failure. It is a car sound you should never ignore. Usually caused by defective rod bearings, the knocking sound coming from the engine rod should be fixed as it can lead to crankshaft damage.

Engine Misfires

A car engine connecting rod failure can disrupt the smooth operation, which can cause engine misfires or irregular combustion. This can result in reduced power, poor fuel efficiency and increased exhaust emissions.

Increased Engine Vibration

As connecting rods lose their structural integrity, the vibration increases throughout the engine. Malfunctioning engine rods can be a reason your car vibrates when idling. Excessive vibration can lead to further damage to other engine components.

Engine Overheating

A car connecting rod failure can lead to increased friction and heat generation within the engine. This may contribute to engine overheating, which can lead to additional complications. Keep a regular check on the connecting rod problems to limit the extent of potential damage.

How to Fix Bad Connecting Rod

Take your car to a workshop for all the bad connecting rod fixes
Take your car to a certified technician to get all the connecting rod-related issues fixed

Fixing such internal parts involves a complex process that typically requires engine disassembly. The problem can only be effectively fixed by a certified auto technician. When a car has engine connecting rod issues, visit an auto garage in Dubai or other emirates for optimal results. 


How is the piston and connecting rod connected?

A piston pin or wrist pin links the piston and the rod. The purpose of this pin is also to carry and transfer combustion forces.

What is the difference between a piston rod and a connecting rod?

A piston rod and a connecting rod are often confused as the same part, however, they are not. A piston rod is a piece of rod connected to a crosshead that helps pistons reciprocate. On the other hand, a connecting rod connects the piston to the crankshaft, facilitating engine functioning.

This was everything to know about the engine connecting rod. Note that the location and functioning of the aforementioned parts may depend on the type of car engine layout. Moreover, to add to the vehicle’s longevity, make sure that its engine is running fine. For this purpose, keep a close check on reasons why a check engine light turns on.

A thorough engine inspection is also necessary when buying a used car for sale in the UAE. Keep all these things in mind to make a well-informed purchasing decision.

For more information on important car parts and repairs, keep reading dubizzle Cars’ blog.


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