Connecting Rod


Connecting Rod

Nine out of ten cars on the road today come with one of the most common engine designs. The most popular types of engines are four-cylinder and six-cylinder ones. However, you may also find eight-cylinder engines and even more exotic and luxury configurations with ten, twelve and even sixteen cylinders.


Regardless of a car’s engine design, each cylinder has a connecting rod inside it, which is a thick flat piece of steel or, sometimes, another metal. This engine part connects the piston with the crankshaft, allowing the piston to transform its up-and-down reciprocating motion into rotation motion of the crankshaft. The power produced by all cylinders, firing in a controlled manner, is delivered to the wheels by means of the car’s transmission, moving the car forward.

When do you need to replace a connecting rod?

A failed connecting rod is usually a sign of another engine problem. Designed to survive the test of time it almost never fails on its own, however, may get malfunctioning due to a lack of maintenance and the failure of another part. Here are the most common signs and symptoms of a bad connecting rod:

-Knocking sounds from the engine: What we usually call “rod knock” is caused by poor lubrication, especially at the bearings where the vertical motion of the connecting road is applied to rotate the crankshaft. Due to the absence of normal film of oil allowing the moving parts to move smoothly, the bearings quickly wear away because of the metal to metal contact between the crankshaft and connecting rod. You may also have a “spun bearing” when the bearing loses its position and blocks the oil transfer through the oil passages. Both problems will cause a knocking sound, which is more noticeable at a steady engine rpm speed and will become louder at higher engine speeds.

-Lack of oil/oil pressure: This is another symptom of insufficient lubrication. It happens because of dirty/sludgy oil that blocks the engine’s oil passages making it harder to circulate through them. This will also cause your oil warning light to illuminate and your oil pressure gauge to show low readings if you have them on the dashboard. In case it happens, cut off the engine and call your mechanic since the lack of lubrication may seriously damage your engine.

-Increased oil consumption: The root of this issue is mostly described above. Poor lubrication may lead to increased oil consumption, so if you have to add oil on a regular basis it’s time to get in touch with your mechanic and check your engine.

-Overheating engine: The lack of oil lubrication increases the amount of heat produced by the engine that your cooling system cannot overcome. Once you notice your temperature gauge hits its red zone or the temperature warning light comes on, cut off the engine and call your mechanic.

Should I drive a car with a bad connecting rod?

The right answer is definitely not. A poor connecting rod will quickly become the source of serious and often catastrophic engine problems even if you drive it several times. If it gets broken at high speeds, the connecting rod can destroy the engine block and even make a hole in it. In addition, the piston that is now free to move will do a lot of damage at the top of the cylinder including, but not limited to, bending or breaking intake and exhaust valves. Known as “throwing a rod” this event usually means the death of your engine.

How can I fix a connecting rod?

Almost always a bad connecting rod is synonymous with serious engine damage. Even if you catch the problem before your engine is totally destroyed, there will be a lot of stuff you’ll need to replace. Here is a list of parts that may need a replacement or repair:

  • Broken or damaged connecting rods
  • The connecting rod bearings
  • The pistons and piston rings
  • The crankshaft
  • The intake and exhaust valves
  • Other engine parts

To compile the list of required engine parts your mechanic will have to disassemble the motor. The labor itself and parts that need replacement will cost a pretty penny. 

In the event you face such a misfortune, you’ll need to make a difficult decision. Depending on the cost of damaged parts and the overall condition of your vehicle, you’ll have a couple of options to choose from.

  • repair the engine having replaced all damaged parts
  • replace the engine with a remanufactured one which is covered by a warranty
  • purchase a used engine with no warranty
  • sell your vehicle to a scrap yard as it costs less than the replacement parts and labor

The options are listed in order of the repair cost and engine damage. The first one is good for an engine with minimal damage, while the second one will meet your needs if you have an almost new vehicle. The purchase of a used engine will work for an older car if you want to keep it running longer. The final option is the way to go if you drive an old and worn car that costs as much as its repair.

Can I replace a failed connecting rod myself?

Unless you’re a professional mechanic with plenty of years of experience in this field, no, you can’t. Repairing an engine is not a typical job and requires sophisticated skills and specialized tools.  

Can I prevent its damage?

Preventing connecting rod problems is one of the best and cheapest ways to keep your engine running for years to come. It is much easier and cheaper than having to pay a lot of money for labor and repairs.

If you try to save a couple of dollars by not maintaining your car properly, it’s a high-road to expensive repairs. Changing your oil at the recommended intervals as well as following the manufacturer’s recommendations in your owner’s manual is a perfect insurance against any car problems including bad connecting rods. 

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