Rod knock or persistent knocking sounds from your engine is always a sign that your engine is about to fail. Not taking action will mean that you need a new engine or a new vehicle.
That should be obvious from signs like power problems, trouble starting, and reduced acceleration. However, most people start to notice rod knock because of the persistent tapping or knocking sound coming from under the hood.
That’s the bearings – which wear down and create a knocking sound.
Unfortunately, rod knock repair has an average cost of $2,500, ranging from about $1,400 in the best case scenario to over $4,500 in the worst case scenario.
On average, it will be almost half of that. And, most of that cost is labor, as the bearings for the pair should cost somewhere between $25 and $1,200 depending on what you get. The rest is labor, with 8-20 hours needed to replace the bearings.
The table below shows a quick price comparison of rod knock repair cost estimates from reputable suppliers:
|Supplier||Rod Bearing Cost||Labor|
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How Much Does Rod Knock Repair Cost?*
The largest part of the cost of repairing rod knock will always be that of labor. However, parts can be expensive as well. However, on average, you’ll pay less than a few hundred for the parts and the rest will be labor charges.
The chart below details the cost estimates for different vehicles:
|Vehicle||Rod Bearing||Labor Cost|
*Note: Prices are estimates and we’re correct at the time of writing June 2023. Cost estimates may have changed since, our figures should be used as a starting point for your own research.
What Is Rod Knock?
Rod knock is literally the sound of a rod from the engine knocking against the crank case as it changes direction. This happens when you’ve spun a bearing and the bearing is no longer protecting or properly rotating the rod as it spins.
How does it happen?
Your engine is built with a gap tolerance between the bearing surface and the crank journal – which allows you to lubricate the bearing. As the bearing wears down, the oil is no longer thick enough to provide a barrier, meaning that the bearing can “knock” against the case.
Of course, this issue might also be crank case damage, low oil pressure, or a damaged bearing. However, you can normally expect to have to replace the bearings at least once over the lifespan of a car – although bearings can easily last 100,000+ miles.
Rod Knock Repair Price Factors
Repairing rod knock will depend on the vehicle, the local cost of labor, and even the source of the damage.
If the knock has been going on long enough, there might also be other damage, which means you might have to pay for more costly repairs as well.
Local Cost of Labor
The local cost of labor can vary quite a bit from place to place. This means that you’ll pay anywhere from $15-$210 depending on where you go and who you pay.
If you take your vehicle to the dealer, you can always expect work to cost over $100 per hour. Most chain shops start at around $95.
However, if you’re going to a general mechanic, rates average between $50 and $95. And a small mom-and-pop shop may charge much less.
That’s important, considering you’re going to pay for at least 8 hours of labor for the job. In addition, that could be over 20. You’ll also have to factor in shop fees, which are 5-20% of the fee, and any lot fees (usually $5-$25 per day).
So, if you need 20 hours of your mechanic’s time, the job is likely to take over a week, because they have other clients too. So, you could pay as much as 5 days of lot fees alone, plus up to $4,000 in labor.
Your engine will impact the cost of fixing rod knock because different engines have a different number of rods and bearings. For example, a four-cylinder engine may only have three bearings.
However, most four-cylinder engines have 8-12 main bearings and double that of rod bearings. You’ll have to individually take apart both cylinders and replace 4-6 bearings per cylinder. On the other hand, if you have a V8 or a V10, you could have 16-24 main bearings and up to 50 rod bearings. That means spending more on parts and taking more time in labor to replace the bearings.
Of course, bearings are typically cheap. You won’t usually pay much per. However, the time and labor can add up a great deal.
Difficulty of the Job
Some engines are relatively easy to disassemble and repair. Others are not. For example, a larger engine area will make it easier to lift and access the cylinders, which means you can more easily replace the bearings. Smaller engines usually require much more work.
That’s also true if you have an unusual car or one that your mechanic doesn’t know. They’ll take much longer to do the work because they have to see how things are put together as they go.
When your car’s rod bearings start to go out, they will start to cause damage to the engine. Therefore, the sooner you get the issue looked at and fixed, the less the total job will cost.
However, faulty bearings can result in damage to the gaskets, cylinder head bolts, pistons, crankshaft, and engine block. A spun bearing can literally fuse into the crankshaft, meaning you’ll have to replace that as well.
This can mean adding thousands to the cost of the repair, and it may mean that you’re better off rebuilding the engine or replacing it.
4 Symptoms Of Rod Knock
If your engine is knocking, you’ll hear it. It’s called rod knock for a reason. However, there are other symptoms you can look for.
1. Knocking Sounds
If you hear a knocking, tapping, or rhythmic sound of metal striking on metal, it’s a rod bearing issue. That can also be any of the main bearings in the cylinder.
However, it’s always a sign that you should take your car to be serviced and fast. The longer you wait, the worse the damage will be.
2. Symptoms in Oil
If your engine oil is full but you can’t keep oil pressure up, it’s typically a case of spun rod bearings. You can also look for symptoms like metal shavings when you change the oil. That might also work out to a silver sheen in the oil – as a result of fragments of metal shorn off the rods or the bearings.
If your vehicle is newer than about 20 years, it submerges the bearings in engine oil to reduce friction. However, when you spin a bearing, the bearing will start to wear down into the engine oil, which will show symptoms in the oil, in the filters, and even in contamination in the gas.
3. Transmission Problems
Rod bearing issues can prevent force from transferring properly between the engine and the transmission. This often results in transmission issues. For example, your transmission might grind. The flywheel or crank wheel might grind or wear down.
In general, noise from the transmission is bad and it’s not necessarily a bearing issue – however, if it’s combined with other symptoms here, it could be. And, if left alone, it could result in transmission failure.
4. Engine Failure
A spun bearing can turn into engine failure when the bearing throws the rod. Or, you could fuse the crank to the bearing, meaning that your engine no longer operates.
In either case, you’ll have to replace the crank – which will likely mean you’ll just want a brand-new short block for your engine.
How Do You Repair Rod Knock? (Video)
Repairing rod knock is a difficult and time-consuming job. It’s not something you should do without professional equipment, as you’ll have to drop or lift the engine.
Doing so without a good hoist or cherry picker is extremely difficult and difficult to fix if things go wrong. An engine block typically weighs 300+ pounds, which means it’s unlikely you can get it back.
Things you’ll need
- A wrench set (check your vehicle to see if you need imperial or metric)
- Ratchet and socket set (check your vehicle to see if you need imperial or metric)
- Breaker bar
- Service manual for your vehicle
- Replacement bearings
- Allen/Hex wrench set
- Bearing lubricant
- Brake cleaner
- Plastigauge or equivalent
- Torque wrench
- Drainage pan
- Shop towels
- Check your service manual to see if you have to remove the engine to access the cylinders.
- Follow safety precautions and park your car on a flat surface. Chock the back wheels. Pull the key from the ignition and then unplug the battery from the left negative post.
- Drain the engine oil.
- If you have to pull the engine, remove everything in the way. Here, you’ll typically have to pull the air intake, the spark plugs, the starter, the coolant hoses, radiator support, accumulator, high pressure lines, heat shields, connector brackets, sensors, oil pump, steering shaft, steering hydraulics, the throttle bodies, etc. From there, you can attach your cherry picker or hoist or put a lift under the engine and then unbolt the motor mounts. Do not do so without first stabilizing the engine, as letting it drop can damage the engine. The process is a bit different per engine, so check with your service manual to see what you actually have to take out.
- With the engine stripped and accessible, unbolt the bearing caps from the engine. Mark them with paint or chalk. If they’re stuck, using a hammer and screwdriver to pop them off.
- Rotate the crankshaft clockwise using a ratchet to manually rotate it.
- Remove the bearing rod caps from each throw as it turns into view.
- Thoroughly clean each one as you go. Use brake cleaner to clean the caps and the rods.
- Remove the bearing shells.
- Check for debris or damage in each and clean everything out.
- Then, install the bearing shells, starting with the lower halves. Align the holes with the ones in the rod caps and make sure it locks into place.
- Then repeat the same process on the upper end.
- Use a thin layer of lubricant between the layers.
- Replace the rods, starting with the big rod end.
- Use either plastigauge or a set of calipers to install these to manufacturer’s specifications.
- Connect the rod caps.
- Finish replacing and torquing down the bearings before rotating the crankshaft.
- Rotate the crankshaft clockwise and put back the bearings at each point.
- Put back the bearing caps.
- Reinstall the engine in reverse order. Make sure you refill the engine oil and allow the engine to idle before going for a test drive.
If you still have questions about repairing rod knock, these answers should help.
Is rod knock worth fixing?
It might not be worth fixing the rod knock. Normally, it depends on what your engine costs secondhand and what it costs to simply rebuild or replace the engine.
For example, if you can buy a refurbished short block and have it installed for a total of $3,500, you wouldn’t want to pay $4,000 to replace the bearings.
On the other hand, if you have a V8 and the engine is in good shape, you’d probably pay over $10,000 for a new engine, so replacing it will likely be cheaper.
Is it bad to drive with rod knock?
The longer you drive with rod knock, the more likely it is that your transmission and your engine will go out.
Therefore, you shouldn’t drive with rod knock unless you want to replace the whole car or the full powertrain.
Can you fix rod knock by adding oil?
You cannot fix rod knock by adding oil. Low oil pressure may contribute to the problem.
However, it’s more likely that the oil issue is because of a bearing issue, and adding oil will only reduce problems for a few days at most.
Rod knock is a major problem that can mean it’s time for a new car. On average, you’ll spend about $2,500 to fix the issue. Most of that will be labor. Here, you can expect to pay an average of $250 for the replacement bearings and the rest will be labor. However, actual costs can range from $1,500 to over $4,000 depending on your engine, the extent of the problem, and if you have to replace or repair other parts.
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