Symptoms of Rod Knock: Something You Must Be Aware Of

This post may contain affiliate links. If you make a purchase through links on our site, we may earn a commission.

Knowing the symptoms of rod knock can really help you save yourself from big trouble. A rod knock occurs in the engine’s crankcase whenever the vehicle’s rods loosen and begin to hit on each other.

Rod Knock How to Know if its Not Working

A worn bearing is one of the most common causes of a rod knock. We’ll break down all the possible causes and solutions of rod knock so you can get your car back up and running.

Seven Possible Causes of Rod Knock

The seven possible causes of rod knock problems include substandard oil, inadequate or no engine oil, excessive speeding, and a threadbare rod bearing. Aside from these, you could also have a lean fuel-air mixture, low-octane fuel, or a faulty sensor.

– Threadbare Bearings

One of the major causes of a rod knock is threadbare or worn bearings. Bearings are essential for ensuring smooth and controlled piston movement. Over time, these pistons wear out and can come out of their position. The piston rods also rattle against the crankshaft, creating knocking sounds.

Fixing the Rod Knock that Has Problems

Another way to diagnose this is to determine if your engine consumes a lot of oil. If it is, then the cause of the rod knock sound is a worn bearing.

– Poor Oil Quality

High-quality oil is essential when it comes to the proper functioning of your engine. Using dirty or less viscous oil, especially with low oil pressure, can cause rod knocking. Thicker oil and oil in low quantities won’t lubricate your bearings enough and may slowly damage them. The damage can lead to an increased gap between the rods, creating that knocking sound.

Unclean oil also contains particles that can damage your engines and lead to further problems. You should also check the color of the oil. Dark brown means the oil is old and requires an oil change.

– Inadequate or No Engine Oil

Low or no engine oil is another cause of rod knocks. Once the rods begin to wear out, more oil begins to pass through them and the crankshaft. You may start to notice that the oil pressure is lower than usual, and the check engine light might start glowing on your dashboard. This can be used to diagnose rod knock and is a strong indicator of a bad bearing.

– Low-Octane Fuel

Low-octane fuel is also another reason why there is a rod knock. Most cars use high-octane fuel to function correctly. High-octane fuels burn uniformly and prevent engine problems, including engine knock. Therefore, using low-octane fuel can be a significant source of the knocking sound.

– Lean Air/Fuel Mixture

If there is a lean air/fuel ratio, it means there is too much air and not enough fuel. This doesn’t allow fuel to burn correctly and is another common cause of knocking rods. Several factors, including faulty fuel pumps and bad oxygen sensors, can cause it. With a low amount of fuel, the mixture will not ignite enough and explode several times.

– Bad Knock Sensor

The knock sensor is responsible for detecting rod knock. When a situation that can lead to a knock arises, the Engine Control Unit can automatically correct it. However, when the sensor is malfunctioning or bad, the system might allow the engine to keep knocking.

This is no longer a frequent problem in modern cars because the injectors and the engine timing chain are now computer controlled. If you are driving around in a modern car and experiencing an engine knock, you still need to check the sensor, as it is an integral part of the diagnostic process.

– Overspeeding

Overspeeding can also lead to rod knock. The high engine speed will increase the speed of the pistons, which will, in turn, increase the wear and tear of the bearings. It can also increase the heat produced, damaging the bearings’ material. While this doesn’t happen every time, it is a possibility and can cause a detonation knock.

Six Solutions To Fix Rod Knock

The six solutions to fix a rod knock include draining out the bad oil, inserting a new plug, and checking out the crankshaft and bearings for wear and tear. You can also fix the issue by cleaning your gas tank with an injector cleaner.

– Drain Out the Bad Oil

First, grab an oil catch to avoid messing up the garage. Before you drain the bad oil, ensure you find out the oil’s viscosity so you don’t replace the old oil with the wrong oil. Take a cup of the old oil as you check the engine so you can take a closer look. Metal shavings in the oil indicate that there’s a wearing of the engine or its components, which is causing the knocking sound.

Possible Ideas to Fix your Rod Knock

You should also check the color of the oil. A dark brown oil indicates that the oil is old or dirty and needs to be replaced. Similarly, an oil that is too light needs to be replaced too. A perfect way to extend the life of an engine with rod knock is to change the oil at the proper intervals.

– Remove the Oil Pans

Remove the oil pans and drain the oil from the engine thoroughly. Reinsert the draining spark plugs and remove the oil filter by turning it clockwise. Insert a new filter and assemble it to recommended specifications.

If you don’t know the volume your engine needs, check the oil level as you pour in the new oil. A four-cylinder engine needs about 4-5 quarts.

– Check for Worn Connecting Rods

Check each rod for excessive wear or tear by rotating the engine with one hand while holding each of the rods in turn. Even if they seem solid, inspect the connecting rods by removing each from the engine. The rods should be perfectly smooth with no wear markings.

– Inspect the Bearings

Remove the pan and check your rod bearings. If they are loose, you will hear a knocking in your engine. Tighten or replace the bearings as needed. If they are the wrong size, you might need to replace them.

– Inspect the Crankshaft

With the rods removed, check the condition of the rod journals on the crankshaft. This is part of the crankshaft that rotates in the bearing. If there is a sign of wear or tear, you might need to replace the crankshaft.

The crankshaft might not need to be replaced if the rod journals aren’t damaged. In this case, an engine rebuild might not be necessary as only the rods and caps must be replaced. But if the crankshaft journal has been damaged, then the crankshaft will need to be replaced.

– Use Fuel Injector Cleaner

While refilling your tank at the gas station, grime and dirt might make their way into your gas tank and cause a rod knock. Cleaning your fuel injection system can clear out the dirt and stop the rod knock. For older vehicles that use carburetors, do not use a fuel injection cleaner; instead, use a carburetor cleaner and clean out all the grime.

Frequently Asked Questions

– Are Rod Knocks Worth Repairing?

Yes, a rod knock is worth repairing if your vehicle is in good condition and has been adequately maintained. However, if it is old and of low value, you may not need to do a rod knock repair. Weigh all options and repair costs before making a decision.

– How Far Can You Drive if You Have a Rod Knock?

Not far, as driving with a rod knock isn’t recommended. Once a rod starts to knock, there’s no telling how long it will take before the engine blows. With bad timing, this can leave you unexpectedly stranded.

– What Are the Signs That You Have a Rod Knock?

The signs that you have a rod knock include loud sounds from the engine, low oil pressure, contaminated oil, as well as driving noises. Once you see or notice any of these symptoms, you need to drain bad oil. You can also do other checks, like checking for worn rods and inspecting bearings. If you have little experience fixing cars, consult an expert mechanic as soon as possible.

Complete Guide for Your Problems with the Rod Knock


You don’t need to panic anymore if you have a faulty rod.

Here’s a recap of the main points discussed in the article:

  • Rod knocks are the sound you hear when one or more of your connecting rods are hitting the crank when changing direction. The A rod knock can occur because of poor quality oil, low or no oil, and a worn rod bearing.
  • Other reasons include low octane fuel or a faulty sensor.
  • Solutions for fixing rod knock include draining the oil and checking the bearings.
  • You can also replace the crankshaft as well as the rod bearings.

With the information in this article, once you notice a rod knock in your vehicle, you can diagnose and fix the problem immediately. Even if you must go to the mechanic, you will understand how to get the perfect repair for your specific issue.

5/5 - (17 votes)
Ran When Parked