What is Rod Knock? Causes, Symptoms and How to Fix it

Rod Knock usually occurs when one or more connecting Rod holding the Piston and crankshaft which allows its free to-and-fro movement starts wearing off.

Rod Knock is a major issue in automotive and can its symptoms sometimes be likened to other faults such as Detonation, Piston slap, Piston pin ticking and Valve train ticking noises.

This has made many car users sell off their cars because if the Rod Knock isn’t addressed on time it could further break, destroy or knock the car engine.

In this article, I’ll be teaching you what a Rod Knock is, the sounds, symptoms, prevention and also how to repair a vehicle that ran into a Rod Knock.

What Does a Rod Knock Sound like

One of the symptoms to expect if your vehicle runs into Rod Knock is the noise that comes with it.

This Rod Knock sound or noise is a result of one or more surfaces or connecting rods hitting or pinning against the crankshaft.

The pistons and crankshaft are joined by the connecting rods. And there is a bushing (often referred to as a roller-bearing) made of softer metal in between the bearing rod and the crankshaft.

In order for the calliper to sit in the crank journal, vehicle engines are by default manufactured with a clearance tolerance. Because of the narrow clearance, engine oil can flow over the metal surface without causing early wear and tear. However, with time, the metal calliper that connects the connecting rod to the crank will begin to corrode, which will cause the rod to knock.

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Symptoms of Rod Knock

Below are a few noticeable symptoms you’ll experience if you’re car runs into Rod Knock.

Knocking Sound:

As the name implies, you’ll continuously hear a deafening sound like that of someone hitting a metal beneath your car. The noise will increase if you press the gas pedal.

Overheating:

Excess pressure on the Piston and bearing material will definitely cause your vehicle to overheat.

Low Oil Viscosity:

When engine parts such as the crankshaft and its bearing start wearing out, the Viscosity of the oil in the engine will decrease.

Causes of Rod Knock in Vehicles

Rod knocks are mostly caused by wear and tear of engine components which can be related to the low oil level.

Over time, the engine’s motor oil loses its viscosity, fluidity rating, and moisturizing characteristics as it passes through the engine. All of these cause internal corrosion and the accumulation of sludge in the engine.

Low oil pressure & improper oil circulation will occur if you drive your car with low oil levels.

This might cause severe engine damage and wear. Rod knocking may also result from several other mechanical issues.

Several causes of Rod Knock include;

  1. Inadequate oil flow into the bearing surface
  2. Immoderate combustion pressure
  3. Faulty Flywheel
  4. Worn out Of the main bearing
  5. Overreving the engines – High Poston inertia force
  6. Excess oil temperature
  7. Inadequate oil pressure
  8. Low oil viscosity & Pressure
  9. Bad alternator rotor bearings.

In order to diagnose if the problem is really a Rod Knock, you can proceed to diagnose your vehicle by checking the oil level on your car or performing an oil change.

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How to Repair Rod Knock

A rod knock is just a warning that there is a problem with an engine’s internal components. This does not imply that your engine cannot be fixed.

However, there are a few things you can try to lessen the rod knock and maybe stabilize your engine before making a comprehensive repair, so do so before calling your dealership or mechanic.

1. Change Oil and Oil Filter

Since rod knock is mostly caused by bad oil in the car engine. You might consider changing the oil with its oil filter to permanently get rid of dirty oils.

You can do this from beneath your vehicle by unbolting the oil drain plug.

Also, remove the old oil filter and replace it with a new one in case of Dirt and particles that have been accumulated to decrease oil pressure and purity.

You can look up our article on how to change Engine Oil for proper guidance.

2. Check the Connecting Rods

If the problem persists after an oil change, you might consider performing a visual inspection on the connecting rods.

Also, check out for loose bolts and tighten them. You can also change the con rod totally.

3. Pour Fuel-Injector/ Carburetor Cleaner into your gas tank

Dirt particles get passage into your gas tank and then to the engine which might eventually cause blockage.

Cleaning your fuel injector or carburettor ( for older vehicles) will get rid of particles in the fuel injection system and will help curb rod knock.

4. Use heavier Oil or additive

5. Avoid oil levels dropping very low

6. Don’t allow coolant into your oil.

7. Replace the Rod bearing

Implementing one or all of the above fixes will stop or reduce the rate at which your vehicle runs into Rod Knock.

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FAQs

Is it worth fixing Rod Knock?

Yes, as a matter of fact, rod knock is a signal that there’s a major issue in your car engine and should be addressed immediately.

Failure to address the issue might cause problems to other parts of the engine.

Can I still drive with a rod knock?

No, it isn’t advisable. Driving with a rod knock endangers your life and that of other road users.

It’s necessary that you park at a safe place and fix the problem if you don’t want to further complications.

Will adding Oil solve Rod Knock?

It might solve the knocking Sound temporarily which will come back after some time.

It’s important that you perform a total oil and oil filter change for maximum engine performance.

Can you hear rod knock at idle?

Yes, Rod’s knock is audible during startup, idling, acceleration, and deceleration of the engine. Stepping on the gas pedal will make the noise get louder, and removing your leg will make it get quieter. Anyone who tells you otherwise, ignore them. Why? Rod knock is a loud banging sound that occurs when the engine first starts and lasts until the automobile is turned off.

Conclusion

One of those problematic engine issues that many people misunderstand, considering it to be the end of their car’s engine, is rod knock.

If you identify the symptoms head and act fast, your mechanic or dealership might be able to fix it without going over budget. However, if you see the warning signals mentioned above but ignore them, addressing the problems could be quite expensive. Your engine replacement may be your only alternative at this stage.

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