How Much Does It Cost To Fix A Rod Knock?

What triggers an engine to knock, and what steps should you take to stop it? It might be a rod knock!

This happens when the crankshaft journal and bearing clash, producing a knocking sound and connecting the crankshaft to each cylinder’s connecting rod. Rod knock will rapidly worsen if neglected, leading to more damage and, thus, a higher repair expense.

Never let your engine produce a sound called “rod knock.” Because the repair costs will almost always be very high, you can identify if your engine has a rod knock by looking at the below symptoms.

You can begin to notice a terrifying engine noise known as rod knock when your automobile idles. It frequently sounds like a loud banging noise that is enough to stop your heart as you think about the pricey engine repairs. Not all engine bangs, though, are rod knocks.

Rod Knock? What Is That?

A deep tapping noise from inside the engine is called a rod knock. It results from rod bearing wear or damage. The connecting rod bearings in the car have too much clearance, which results in extra movement.

The knocking sound is made as the piston reverses direction and metal begins to strike metal. As the load and speed grow, this noise will get louder.

If you’ve heard a rod knock, you can recognize it immediately. When you crank your engine and depress the throttle, you’ll frequently hear loud bangs coming from your engine. You often listen to it right after you let off the gas.

A driver looking problematic with his car’s issue.

What Causes Rod Knock?

Rod knock is most frequently caused by connection rod bearing wear. Although there is only one cause of rod knock, several different factors can result in symptoms comparable to rod knock.

The following are some of the factors that could result in rod knock or symptoms that are similar to rod knock:

1.     Worn Bearings

Bearing wear is the sole reason for the rod knock. The crankshaft, which transmits power to the wheels, rotates as your engine pistons rise and fall. The bearings are in charge of maintaining the smooth, controlled movement of the piston.

However, these bearings might lose their position due to wear and tear over time. When the bearings are worn, the piston rods start rattling against the crankshaft, producing a distinctive knocking noise. The engine’s deep-seated bearings must be replaced to fix this.

2.     Low Octane

A knock from an explosion may resemble one from a rod. The air and fuel combination burns in each cylinder in a single detonation if the engine operates as it should. On the other hand, the detonation knock happens when that mixture explodes multiple times at once, producing a banging sound.

Octane that is too low for the engine is one such reason for this knock. You require a higher octane level than typical cars if you have a performance engine. High octane avoids that knock by burning consistently.

Using a higher octane fuel the next time you fill up the car will solve this issue.

3.     Poor Timing

Bad engine timing is another cause of the detonation knock. The timing describes when the spark plugs ignite.

Auto mechanic working on an engine valve.

The computer is in charge of timing. When the timing needs to be corrected, the spark won’t ignite when it should, resulting in several cylinder detonations.

This brings the detonation knock-on. The timing needs to be fixed to address this.

4.     Lean Air/Fuel Mixture

Lean air/fuel mixture is another factor in detonation knock. Oxygen sensors, fuel injectors, a broken fuel pump, and mass airflow sensors might all be to blame for this issue.

When there is too much air and insufficient fuel, the result is a lean mixture. Multiple detonations result from the mixture’s inability to burn quickly enough with inadequate power.

5.     Bad Knock Sensor

A broken knock sensor is another cause of detonation knock. Fortunately, this only happens sometimes because the air/fuel ratio, timing, and fuel injectors are computer-controlled in more recent vehicles.

The knock sensor recognizes any circumstance that might be causing the noise and alerts the ECU so that immediate corrective action can be taken. Therefore, if the car’s knock sensor is malfunctioning, the computer won’t know how to fix the problems and may let the engine knock.

6.     Bad Belt Tensioners/Pulleys

The last potential cause of an engine knock is something that isn’t even coming from the engine. Similar noises can be produced when the auxiliary belt needs to be correctly tensioned.

The belt turns when the engine turns. It is attached to multiple pulleys in the engine bay and needs to be pulled precisely to operate smoothly and quietly. If the belt becomes loose, the tensioner needs to be fixed.

Taking off Belt Tension Pulley from car engine.

However, if one of the pulleys bends, you can also experience issues. The rattling, slapping, and clicking noises that result from this situation could be misinterpreted as an engine knock. You only need to change the belt, tensioner, or pulley to get this right.

How Much Are Engine Rod Repair Costs?

The rod knock repair will cost at least $2,500. A connecting rod repair on a select few cars, like a Subaru Forester, may cost $5,000 or more in components and labor.

It isn’t easy to replace connecting rod bearings. The problematic component is firstly deep into the engine. You will require new engine gaskets and seals, cylinder head bolts, and connecting rod bearings.

The lines for the cooler and machine both need to be flushed. Sometimes, you will also require new timing chains, crankshaft, camshaft, connecting rods, pistons, and piston rings. It might be wiser to replace the engine due to the additional parts needed.

Is It Worth Fixing A Rod Knock?

Rod knock is a significant problem with your engine because it indicates a malfunction. Rod knock is a severe issue that won’t go away on its own; instead, you must move quickly to replace the rod bearing and repair any other components contributing to the sound. You could completely replace the engine if you respond later.

Warning: Many drivers consider disregarding the rod knock and continuing to drive. That’s never a good idea, though, and even if we say it’s not worth fixing your rod, you should still consider the issue.

Because of this, if you encounter such problems with your car, you should consider whether the moment is right to sell it. It’s difficult to say that many customers are awaiting your car because they might not be eager to purchase a vehicle with a rod knock.

As a result, you will have very few options, and you must accept this and be honest with yourself about your options.

The good news is that Cash Cars Buyer is one of the very few businesses that will buy your car regardless of the circumstances. What challenges do you face? Cash vehicles buyer is always available to assist you with rod knock or any other serious issue!

How Long Can You Drive With Rod Knock?

There is no conclusive response to this query. Once they experience a rod knock, some automobiles immediately switch off. Other automobiles may squeak for months or even years due to rod knock. If you notice a rod knock, bringing the car in as soon as possible is better.

A car that has a rod knock also experiences recurring engine damage. Under the hood, the metal-on-metal contact will eventually destroy the engine.


When dealing with a rod knock, you should always consider whether it is worthwhile to fix it. The answer to this question greatly depends on a variety of variables. One of the best automobile removal firms in the country, Cash Cars Buyer promises to pay you top dollar and offer free towing no matter where in the United States you reside.

Things will get worse as you wait longer. Any way you look at it, the repair will be expensive. However, taking care of it immediately rather than delaying can soon mean needing an engine replacement or a repair.

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About Matthew Webb

Hi, I am Matthew! I am a dedicated car nerd! During the day, I am a journalist, at night I enjoy working on my 2 project cars. I have been a car nerd all my life, and am excited to share my knowledge with you!

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