What Is Rod Knock? What to Do If You Hear a Rod Knock Sound

What is a Rod Knock sound (Engine Knocking)?

Learn to Diagnose and Fix Engine Rod Knock

Does your car sound a little different than usual? If you hear a knocking sound in place of the typical smooth start of your engine, your engine probably has what is referred to as rod knock, a type of engine knock. 

There are 2 issues “Engine Knock” can refer to:

1. Pre-ignition, Detonation

2. Lower End Rod Knock

In this article, we’ll be explaining the 2nd issue: Rod Knock. What does it mean and what causes it? Watch this video to find out: 

Why Does My Engine Knock? Why Oil Changes Are Important! 

What Is Rod Knock? 

Rod knock is a rapping noise coming from the engine. This noise is caused by damage or wear to the connecting rod bearings. When there is wear or damage to the bearing, this will cause a change in the clearance between the connecting rod and crank. When there is excessive clearance between the rod and bearing, this will cause the knocking sound.

Is Rod Knock Dangerous?

Rod knock is a serious issue. It’s indicating significant wear and/or damage to vital engine parts. Rod knock can be dangerous if the bearings have excessive wear and/or damage. A sign of excessive wear/damage is when the engine is running you will hear a constant loud rod knock sound.

Can I Drive a Car with a Rod Knock Sound?

If a rod knock sound is coming from your engine you should not be driving the vehicle. If you continue to drive the vehicle with severe rod knock, this can result in complete engine failure while you are driving.

Why is this dangerous? Engine failure will result in loss of power, and loss of power can result in loss of power steering, reduced braking and possible engine fire if the failure makes a hole in the engine block, spilling oil onto hot exhaust.

What Are the Symptoms of Rod Knock? 

A sign of rod knock is excessive wear/damage when the engine is running. You will hear a constant loud knock noise.

What Causes a Rod Knock Sound? 

The main cause is the lack of proper oil change intervals and low oil level. Oil over time will lose its lubricating properties, cause sludge to form in the engine and it can cause internal corrosion. Running an engine without the proper amount of oil will result in lower oil pressure and not being able to get oil to all the places it needs to be, causing more friction and excessive heat between vital engine parts.

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How Do I Diagnose and Fix a Rod Knock Sound? 

Check the Oil and Oil Level 

  • Pull out your oil dipstick
  • Wipe the dipstick with a rag. If the oil on the rag is dark or muddy looking, that means your oil is dirty
  • Reinsert the dipstick and pull it out again to take a closer look.
  • Find out how low your engine oil is. Low and dirty engine oil can cause engine knocking and damage
Check Your oil for sludge using the dipstick. Cause of engine knock sound.

Drain the Oil and Inspect It for Any Metal

First, make sure you have an oil pan set up to avoid spilling or staining other surfaces. Your oil cap should say which type of oil your vehicle requires, which is important to know so you use the right kind. Before draining the oil into the pan, use a clear disposal cup to catch about half a cup of oil first to help you get a clearer look at your oil. Once you have that sample of oil you can drain the rest of it into the pan. 

If you see metallic pieces in the oil, those are fragments of the crank bearing. If you don’t regularly change your oil, the old and dirty oil will start to corrode the crank bearings’ brass layer. This result tends to be more common in the crank bearings that are the furthest from the oil pump because they end up receiving less of the remaining oil than the bearings closer to the pump. 

You should also inspect the color of the oil as it drains. If it’s a dark brown, that indicates that the oil is dirty and/or old, which can cause engine knock because it affects the oil’s ability to properly lubricate the engine. 

Is Rod Knock Fixable?

Depending on the damage, your vehicle may require a new engine. You may be better off replacing the vehicle entirely depending on the cost.

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Hearing a Rod Knock Sound? - Diagnose Engine Rod Knock - 1A Auto
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Hearing a Rod Knock Sound? - Diagnose Engine Rod Knock - 1A Auto
Some people ask what is rod knock and others want to know how long can you drive with a rod knock sound. It is simply a knocking noise from the engine and you should not drive it. Find out why here.
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1A Auto
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