What Causes Rod Knock and How to Fix It

Every time you hear a disturbing sound like somebody is knocking underneath the hood of your car with a sledgehammer, that could be a sign of a rod knock.

The sound becomes even much louder when you rev up the engine. Some people may also refer to this sound as engine knock, spark knock, or engine pinging. So you may ask - how to fix rod knock effectively.

Yes, It's important to pay great attention to engine noise occasionally. The engine is a complex system in which both air and fuel are ignited together to move the pistons. These pistons are located on the crankshaft, a part of the engine which is tasked with rotating the wheels.

What Causes Rod Knock?

Before you get started on what causes engine knock, it would be a good idea first to understand the relationship between the crankshaft and the pistons.

This piston usually moves up and down because of the ignition that takes place in the spark plugs.

On this same occasion, a rod connects the piston head to the crankshaft which allows the bearings located underneath the crankshaft to turn both the rod and crankshaft simultaneously.

Because some overheating may occur due to friction, engine oil is normally used to stop this problem and ensure that all moving parts of the engine continue working normally. 

Rod knock often occurs when the bearings start to wear out, which is evidenced when some metal parts start colliding and grinding against each other.

This particular occasion is followed by a knocking sound underneath the hood, and the sound gets even worse when you rev up the vehicle.

Rod knock could also occur from diminishing engine oil levels due to insufficient lubrication between the engine's movable components.

Other factors that could also result in rod knock and the deterioration of bearings include insufficient oil viscosity, minimal oil flow at the bearing surface, high-piston inertial forces, excess oil temperature, and high combustion pressures.

It’s important to have the vehicle checked right away whenever engine pinging occurs. Otherwise, if you choose to ignore this problem, the bearings will eventually break away from the crankshaft and blow out the entire engine as a consequence.

Related: How to clean pistons without removing

How to Fix Rod Knock

You can fix the rod knock in your garage, although you should have all the materials required within reach. Some of these materials include some fresh oil, mechanic's ramps, oil pans, oil-filter wrench, a new oil filter, and fuel-injector cleaner.

When you have all these materials ready, follow these simple steps to fix your engine and bring it back to its initial position.

Before anything, pull your vehicle onto the mechanic's ramps and park it in a way that allows for easy access to the engine.

#1 Get the Car Ready

Place your vehicle on the mechanic's ramps to help you lift it from the ground level and so that you can access the engine with much ease.

If a mechanic slope isn't around, use a jack to lift the vehicle and support it with jack stands.

#2 Place the Oil Pan

Fix the oil pan under the oil cap to easily drain and collect the oil from the engine parts.

Loosen the oil cap to remove the oil from the engine more effectively and more efficiently. Place back the oil cap after you finish.

#3 Old Oil-Filter Removal

Replace the old oil filter by turning it clockwise with the wrench. The wrench purpose is to remove the old oil filter and to replace the new screen.

Fit a new filter in the slot and tighten it with the wrench.

#4 Replace the Old Engine Oil

Replace the old oil you removed earlier with anew, about 5 quarts of fresh oil should do the trick. Get rid of the oil pan and examine the rod bearings.

If they're loose, tighten them to prevent the knocking sound from recurring when you start the engine.

Make sure to replace the rod bearings with new ones if they're worn out.

#5 Clean the Fuel Injector

Open the gas tank and clean the fuel injector to prevent dirt and grime from collecting in the parts of the engine. The fuel-injection cleaner should do the trick and will ensure only clean fuel is passed through the engine.

The knocking sound underneath the engine should also stop after cleaning.

For a car that comes with a carburetor, you don't have to use a fuel injection cleaner. Simply buy a carburetor cleaner and clean the carburetor by spraying around it directly.

Start the engine and check the motor to see if the knocking sound has faded away.

Flush the engine with some detergent to keep its inside parts clean and to ensure that it runs smoothly. The flush contains strong compounds that are useful in eliminating any foreign materials that could bring about the knocking sound again.

Start the engine and if you realize a lot of smoke after flushing, don't worry much as this is very normal. Allow the engine to run and within a few minutes, the smoke will clear and your engine will start working normally.

Following these steps above should fix your engine and have all its functions working normally. Although if you try this procedure and the rod knock still doesn't go away, you can always take your vehicle to an experienced mechanic and have your engine checked. Otherwise, a lack of immediate maintenance will do further damage to the rods, pistons, bearings, and crankshaft.


Rod knock in car engines often occurs due to worn out rod bearings or low oil pressure. The engine has several moving components that require engine oil to stay lubricated. But on the occasion of oil leakages, these movable parts may start grinding against each other and thus bring about rod knock.

Following the tips shared in this handy guide on how to fix rod knock and what causes rod knock, you won't require to bring your vehicle to a mechanic at any one time.

Otherwise, make sure to familiarize yourself with the different causes of engine pinging so that you may know what to do in case you face this problem in the future.

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