How to Fix Rod Knock: Your Questions Answered

Co-authored by Ed Beery and Jessica Gibson

Last Updated: November 2, 2022 References

Is your car making a noticeable knocking noise? It could be rod knock, which is a pretty serious issue caused by wear between the connecting rods and crankshaft of the engine. If there isn't enough lubrication between these moving parts, the rods can start knocking against the crankshaft, causing bigger engine problems. Because fixing rod knock takes advanced mechanical skills, it's best to take your vehicle to a mechanic. If you've still got questions about how to fix rod knocking, keep reading because we'll discuss causes, costs, and more.

Things You Should Know

Listen for a clacking sound coming from the top of the engine—this means rods are hitting or rubbing against the crankshaft.
Check the oil pressure in your vehicle—a check engine light can mean that the engine's not getting the oil it needs. Always make sure that the vehicle has the proper oil level.
Have a mechanic inspect and replace damaged rods or rod bearings to fix rod knock.

Section 1 of 5:

What is rod knock?

Rod knock is a distinctive sound caused by rods hitting the crankshaft. Rod knock is a pretty clear sound—if you open the hood and turn on the engine, you'll hear clacking or a rhythmic thumping sound. If you're driving when you notice the sound, pay attention to if it worsens when you press on the gas—another sign that you've got rod knock.^{[1]
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- If you open the hood and run the engine, but the sound isn't coming from above, your vehicle might actually have a different problem like lifter tick or piston slap.
- Your vehicle may have rod knock if the check engine light comes on, especially after a few minutes of driving.
- If you've got your vehicle up on ramps and you've drained the oil, replace the filter and oil. This can help stabilize the rods until you can get your vehicle to a mechanic.

Section 2 of 5:

How much does it cost to fix rod knock?

It can cost between $2,000 and $7,000 to fix.^{[2]
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Research source} The cost completely depends on the exact cause of your vehicle's rod knock like whether you need to replace just the rod bearings or the entire crankshaft, but it usually involves extensive engine repairs. In addition to paying for replacement parts, you're also looking at high labor costs since it takes a mechanic anywhere from 8 to 15 hours to make the repairs.^{[3]
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- The earlier you fix the rod knock, the better! Servicing your vehicle immediately can prevent further engine damage.

Section 3 of 5:

What causes rod knock and how do I fix it?

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Rod knock happens when there's not enough lubrication in the engine. The rods and rod bearings are separated from the crankshaft of the engine by a really thin layer of engine oil—this is what normally prevents them from rubbing together. If there's not enough oil, the increased friction will cause the bearing to spin out of place so the rod rubs against the crankshaft. Unfortunately, this means typically means replacing the rod bearings—something your mechanic should do.^{[4]
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Take your car to a mechanic to have them fix it. They'll check the rod bearings for signs of heat damage caused by rubbing. They'll also inspect each rod and rod bearing to see if it's loose or knocking against the crankshaft. Finally, they'll drain the oil and check the oil pan for shimmery metal fragments—these are bits of the bearings, which means the rod bearings are knocking against the crankshaft. ^{[5]
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- The mechanic can also assess if there's damage to the crankshaft, the connecting rods, or the entire engine block.
- Your mechanic should also determine why the crankshaft and rod bearings weren't getting enough engine oil—the oil could be leaking from somewhere in the fuel pathway or the bearings might not fit properly for instance.
- A mechanic might recommend that you clean the fuel-injection system if your vehicle's got shimmery particles in the old oil. The injector cleaner is basically a solvent that can dissolve grime in your vehicle's fuel pathways.

Section 4 of 5:

Will an oil change fix rod knock?

An oil change won't fix the underlying problem that's causing rod knock. Getting an oil change can help with low oil pressure which may be a contributing problem, but unfortunately, it won't solve the mechanical problems of your vehicle's rod knock.^{[6]
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- If the sound is actually not rod knock, but lifter tick, an oil change might solve the problem.^{[7]
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- If the rod knock continues, internal engine work might be required, which is not typically a DIY situation.

Section 5 of 5:

Can I continue to drive a car that has rod knock?

It's not a good idea to keep driving the car until you get it serviced. Simply put, it's dangerous to keep driving the car because it could throw a rod, and that might blow your engine.^{[8]
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- Instead, make your way to a garage where you or a mechanic can inspect the bearings and fix the cause of your vehicle's rod knock.