As you drive your cherished vehicle, you suddenly hear an unusual noise emanating from the engine. It’s a deep, knocking sound that resembles a tiny elf using a ball peen hammer. Is this the alarming rod knock issue? 
Don’t worry, this article will delve deep into the rod knock. Nonetheless, the following questions will be addressed:
- What is rod knock?
- What causes the knocking sound?
- Is it a good idea to drive with the rod knock?
- How can you remedy the rod knock?
- How much will it cost to repair?
Ok, let’s dive in!
Contents
What is rod knock?
Rod knock is the sound of one or more of your rods “knocking” on the crank as it rotates in a different direction. The connecting rod (hence referred to as the rod) is attached to the crank, and between the two is a bearing constructed of a softer material than either the rod or the crank.
There are gap tolerances (measured in 0.001-inch increments) for the bearing to the surface of the crank journal when the engine is manufactured. This little opening allows oil to enter and remain on the bearing surface. Between the two surfaces, the oil coating forms a barrier. As the bearing wears, this gap grows, and the oil no longer forms a suitable barrier, resulting in rod knock.
However, typical wear (which can take hundreds of thousands of kilometers) is not required; damage to the bearing or crank journal can potentially induce early rod knock. Oil pressure loss, filthy oil, and low oil pressure are a few of the issues that can ruin your day.
What Rod Knock Sounds Like!
Rod knock is a tapping sound that comes from within your engine and usually gets louder as you speed up or when the engine is under load. Of course, there are a variety of items that can produce a rod-knock-like noise (see list at bottom), but if you’re dealing with rod knock, you need to know what you’re dealing with. Pro tip: If the knocking sounds disappear once the engine heats up, it’s most likely not rod knock, so examine your exhaust gaskets and other potential sources.
What causes the knocking sound?
A spun bearing, which physically spins at the end of the rod and becomes out of position, is one of the most prevalent causes of rod knock. This is frequently caused by rod cap bolts stretching during really intense driving or poor rod bolt torquing during the build. It could also be the result of a mix of causes.
Here are some other most common causes for rod knock:
- If your timing belt tensioner is loose or broken, it can cause problems.
- When there seems to be an issue with the primary crankshaft bearings.
- The air conditioning compressor is not functioning properly.
- The flywheel or flex plate appears to be either broken or cracked.
- Water pump bearing wear.
- Valves that are sticking or ticking.
- Exhaust leakage.
- Alternator rotor bearings that have worn out.
Check out the easiest way to diagnose engine knock in the video below:
Is it a good idea to drive with the rod knock?
In any case, never drive a vehicle if a rod knock is heard or suspected of being heard, it’s never a good idea. If one continues to use their car in this condition, the damage associated with such a problem might grow quickly. Engine rebuilding would be impossible if a connecting rod separated off an engine’s crankshaft and ejected from the block.
Mechanic John always told me, “It’s not going to fix itself!” when he was teaching me about mechanical parts. This rings true when it comes to rod knock – it won’t go away on its own. It’s a death sentence for your engine, and how long it runs depends on a variety of circumstances. You can sometimes avoid death by switching to heavier oil or applying an additive, but you are merely postponing the inevitable tears because the problem will eventually grow until the engine seizes. The sooner you fix it, the less damage there will be, particularly to the crank.
How can you remedy the rod knock?
To fix the engine, the best solution is to repair it by replacing the bearings and pulling the rods. The flailing rod might have caused harm to the crank journal surface, so it’s necessary to polish it and possibly turn the crank. Turning the crank means grinding down the area where the rod bearing rides, smoothing out the surface, and eliminating any visible scratches.
People often use phrases such as “10 under” to describe this process. However, be mindful that there is a limit to how much a crank can be turned before it becomes useless, and it’s only good for decorative purposes. Once you have finished turning and polishing the crank, it is important to install thicker bearings that correspond to the number of times the crank has been turned.
Additionally, it is recommended to inspect and repair the main bearings of the crank. Take the opportunity to investigate if there are any underlying issues, such as a faulty oil pump, that may have contributed to the failure of the rod bearing.
How much will it cost to repair?
True rod knock is difficult to repair on the fly, usually necessitating an engine overhaul. In most situations, this results in repair expenditures that will leave you with sticker shock. Furthermore, extensive repairs of this magnitude frequently need a significant length of vehicle downtime.
The overall cost of repairing rod knock ranges between $2,500 and $4,500 on average. In some situations, the cost of such repairs can actually exceed these figures, however, this is more likely with imported or high-performance engines.
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Watch the video below to learn more
FAQs
What causes rod knocking?
A spun bearing, which physically spins at the end of the rod and becomes out of position, is one of the most prevalent causes of rod knock. This is frequently caused by rod cap bolts stretching during really intense driving or poor rod bolt torquing during the build.
Is a rod knock worth fixing?
Rod knock is a major problem with your engine since it indicates that the engine is not working properly. If you notice the rod knock, don’t wait for it to go away; instead, take prompt action and replace the rod bearing, as well as any other parts that are causing the noise.
Can you fix a rod-knock engine?
You may require new pistons and connecting rods, camshaft bearings, timing chains, and maybe a new crankshaft depending on the complexity of the repair. If you require all of the extra parts, you should replace the entire engine assembly. A connecting rod repair will typically cost between $2,500 and $5,000.
Read more: Diagnosing Common Engine Noises: Why you shouldn’t Ignore any
Is it safe to drive with rod knock?
If you hear a rod knocking, turn off the engine and don’t even start it again, unless you want to listen to it for a few seconds to figure out what the noise is. The only exception to this rule is driving the car far enough off the road.
Can spark plugs cause rod knock?
Overdue spark plug replacements, as well as filthy or oil-covered plugs, can cause engine banging. Replacing your spark plugs may assist to resolve the problem.
Can an oil change fix the rod knock?
An oil change will not address the underlying issue that is generating rod knock. An oil change can help with low oil pressure, which may be a contributing factor, but it will not cure the technical issues causing your vehicle’s rod to knock.
Will adding oil stop the engine knock?
Adding more oil will reduce the noise, but it will not address the fundamental cause of the noisy engine – the oil leak.
And that’s it for this article, in which we’ve discussed the things you need to know about rod knock. Nonetheless, the following questions will be addressed:
- What is rod knock?
- What causes the knocking sound?
- Is it a good idea to drive with the rod knock?
- How can you remedy the rod knock?
- How much will it cost to repair?
Hope you learn a lot from the reading; if you do, kindly share it with others. Thanks for reading; see you around!
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