What Are The Causes of Rod Knock and How to Fix It?

You should pay attention to the noise your engine makes occasionally.

The internal combustion or the IC engine is a complicated mechanism in which a fuel-air mixture gets ignited and moves the pistons. These pistons are attached to the crankshaft, and it turns the wheels of the car. If the sound resembles knocking from below the hood and it sounds like somebody is using a large hammer to hit your car, you might be experiencing a rod knock.

To confirm this, try revving up your engine and check if the sound becomes louder. Some people also call this problem engine pinging, engine knock, or spark knock.


What Causes Rod Knock Sound in the Engine?

To answer this age-old question, you need to understand the relationship between the crankshaft and the pistons.

Relationship Between Crankshaft and Pistons

The piston goes down and up when the ignition of the fuel-air combination is lit up using spark plugs. The engine uses a connection rod to join the crankshaft and the piston head. On the lower side of the crankshaft, bearings are present to support the movement of the crankshaft and rod. Oil lubrication is used to prevent overheating due to friction and to make sure that all components of the engine are safe from overheating.

Wearing Out of the Bearings Causes Rod Knock

The rod knock occurs due to the wearing out of the bearings, and this makes the metal parts to conflict with each other. Once this constant collision occurs, you will experience a knocking sound. This sound arises when the car is revved up. The loss of lubrication is an important factor when metal parts collide because of the lowering of engine oils.

The rod knock is like the piston slap that takes place due to the wearing out of the wrist pins, which start to wobble around the cylinders.

You should not neglect the rod knock since this problem worsens if you keep driving. With the bearings continuously wearing down because of the friction, the condition gets worse, and ultimately they break off from the crankshaft and blow off your engine.

How To Identify Rod Knock?

Rod knock can easily be identified by a monotonous rattling and knocking sound originating from the engine. This sound becomes more prominent as the rpm increases. If this condition arises only while tarting the car, the problem is due to the main bearing instead of the rod bearings.

The mechanical costs to fix this condition depend on the overall damage. Once additional damage occurs to the engine, you might have to buy a new one. You might need a new oil filter, oil filter wrench, oil pan, and a few mechanical ramps in order to manage the rod knock problem.

Steps to Identify Extent of Damage

  • You will need a mechanic to assist you with the identification of the extent of the damage that took place. If the problem occurred due to low levels of oil, you should change your oil.
  • You should first drive your car to a mechanical ramp. This will levitate the engine to a condition ideal for repairs. Make sure that the hand brakes are on.
  • You should then put an oil pan under the oil drain valve; this will remove the complete oil plug and drain the engine oil. All the oil will get transferred to the oil pan. Make sure that the oil is completely drained, and then it becomes safe to replace the plug.
  • You should remove the oil pan and inspect the rod bearings for tear and wear. This step will require the expertise of a mechanic or a proper workshop manual. You should let the mechanic handle it if you are not sure about the procedure.

Some vehicles contain carburetors that need to be cleaned to limit the dirt and foreign particle accumulation. A major reason for rod knock can be the grime present in the engine. If the rod knock is not fixed, to combat the engine noise, you might need to change the entire engine. Rod knock can also affect significant engine components like pistons, crankshaft, and the rods.

The most important problem is when various bearings can fail simultaneously. Once the bearings wear out completely, the rod will start to grind to the crankshaft.

 How To Fix It

1. Repair Rod Bearings

Once you confirm the rod knock in your engine, you need to repair the rod bearings. Damaged rod bearings can also damage the rods and the crankshaft. You should measure the rods and the crankshaft before you replace the bearings completely to be sure that they are not very damaged.

2. Lubricate Engine Parts and Check for Leaks

One of the main reasons that you get a rod knock is the wearing out of rod bearings. Lubrication of engine parts, especially the ones that are movable, require oil. A prominent reason for oil leakages is a faulty oil pump or a cracked head gasket. If there is no adequate lubrication available for moving parts, your engine will experience much more friction than anticipated and will cause your engine to overheat.

Stop driving the car when you experience a knocking sound. Due to lack of maintenance, there is immense damage to crankshaft, rods, and pistons. 



Rod knock takes place due to the wearing down of rod bears and low oil pressure. Several mechanical moving parts present in the engine need sufficient engine oil to stay lubricated. Once you experience leakages in oil, the movable mechanical parts rub upon each other and cause extreme heating because of friction.

You can distinguish a rod knock from other noises in the engine with the increase in the sound when the car is revved up. You should first explore the option to change the oil. You can either do it yourself or hire a professional.

Once the oil filter is changed, you can put in some new oil. With this, the noise should stop. But if the noise gets even worse, it is an indication that the bearings of your car are completely damaged and need to be changed. If they are not changed, your vehicle might experience even more engine damage.

In this case, you need to consult your mechanic to make repairs or, in the worst situation, get a new engine. Rod knock is a severe problem that requires urgent inspection.