Engine Bearing Failure Symptoms: Causes and Prevention

Engine parts experience a lot of friction due to the movement of engine bearings. For this support, the bearings should remain in good shape. Problems with the engine bearings affect the vehicle’s performance. Therefore, it is crucial to know engine-bearing failure symptoms, and they will help you know when to visit a mechanic.

Engine bearings are made with some of the strongest materials. However, they are prone to fail due to the stress and high temperature in the combustion chamber. The function of reducing friction also puts them at risk of wearing out.

Engine bearings fail due to several reasons. Some causes of this failure are extreme operating conditions and excessive loading. It is advisable to keep the bearing in good shape and replace the worn out.

Failure of the engine bearings can lead to very serious problems in the vehicle. We shall reveal some common symptoms of failing engine bearings, their causes, and how to prevent this common engine problem.

Common Engine Bearing Failure Symptoms

In most cases, an engine bearing failure is due to a damaged engine. There are various symptoms that hint to you that the engine bearing is malfunctioning. Staying for a long time without dealing with the issue will cause more damage to other engine parts.

In some extreme cases, it may cause you to replace the entire engine. It is, therefore, crucial to look out for such symptoms and fix them as soon as possible. Here are the signs of engine bearing failure that you should look out for:

Noisy Engine

Every driver prefers a smooth ride to enjoy peace and serenity. The only sounds you may probably want to hear are those from the car’s stereos. However, as the bearings start to wear out, you will hear some odd engine-bearing noise. Rod knock is the most common sign of a malfunctioning engine bearing.

It produces a noisy sound from the engine, similar to that of valve trains and lifters. This results from excessive clearance due to bearing wear. Thus, the rod’s big end bearing failure causes a grinding contact with the vehicle’s crankshaft, as it starts to beat against it.

Worn Belts and a Noisy Transmission

There are two major faces of a bearing. The first is the main bearing surface, and it is often prone to wear and tear. The second is the thrust-bearing face. The crankshaft works with the main bearing, but the thrust bearing controls the transmission’s movement to an extent.

The thrust-bearing face keeps the back-and-forth movements of the transmission, making it wear over time. Worn-out thrust bearings may move the crank backward and cause it to ram the torque converter into the transmission.

Such incident often occurs when there is sufficient space on the rod journals. This is what makes the transmission make some odd noises. Apart from that, the forward and backward movements from worn thrust bearings could make the belts wear excessively at the edge.

On top of all this, the metal dirt resulting from the torque converter’s force may stick and clog the filter. This makes the fluid lose pressure, and eventually, the fuel pump will break.

Low Oil Pressure

One thing you will notice when the engine bearing starts failing is the loss of oil pressure. The oil pump of vehicles flows a specific fluid amount, and 20 gallons per minute seems standard. Nevertheless, leaks within the engine, like those occurring between the engine bearings and the hydraulic fluid, may cause a reduced oil pressure.

This incident occurs due to the oil that leaves quickly from the channels. In essence, if the bearing starts wearing, there will be excessive clearance between the bearings. This makes the oil pressure go off much more and especially when the pump spins at low rpm. Low oil pressure is a sign that you should never overlook.

Silver Shavings Found in the Oil

Look closely; do you find some silver-like dust particles on the dipstick and in the oil? This is a sign of normal bearing wear, and you don’t need to worry too much. When checking the car’s oil level, you may notice a metal sheen in a powdered form.

If it exceeds that and starts forming a grain-like aluminum substance, then this is a sign of a serious problem. Often, the bearing shaves away when it overheats or lacks oil. In this case, you will see some fine splinters or ribbons in the oil.

If you see any of these signs and symptoms, it is a sign that the engine bearings are failing. Checking the filter media every time you have an oil change will help you detect this problem early and deal with it on time.

Copper Sheen Found in the Oil

Bearings of most vehicles have a 03-layer design. It features a soft outer layer made of aluminum, a copper middle layer, and a backing plate made of steel. The copper provides the last defense line before the wear reaches the bearing steel.

Copper appears softer than aluminum, but it serves the purpose better since it is slicker. The copper layer lasts up to a thousand or two thousand miles. Therefore, you should be able to notice the failure symptoms before the final breakdown.

When the wearing gets to the copper layer, you will notice some copper dust in the oil. So, whenever you check the oil and see a coppery sheen in the oil, the dipstick, or even the valve cover, the bearing is in bad shape. 

Note: Getting to notice these signs early enough will help if you fix the issue quickly. You may search for the engine bearing replacement cost at service stations near you and replace worn-out bearings for proper functioning.

What Causes Engine Bearing Failure?

As stated above, engine bearings are essential for the vehicle to run smoothly, and you should ensure that they remain in good condition. However, bearing failure is caused by different external factors.

So, what causes crankshaft bearings to go bad? For most engine technicians, it is pretty easy to detect the cause of the bearing failing. All they have to do is to conduct a few investigations. You can do it by yourself if you follow a good engine-bearing failure analysis guide.

Knowing the exact cause of engine bearing failure will help you fix the issue quickly. Good maintenance prevents the bearing from facing premature wear. With that in mind, some major causes of an engine bearing failure include:

Debris or Dirt

Dirt or dust can cause major damage to the engine bearing’s surface. Dirt and dust in the lubrication system result in circumferential scratches lodged on the surface of the bearings.

These dirt or foreign particles will often remain in the bearing lining if you fail to clean the filter properly or replace it. Thus, it seems pretty important to keep to a regular cleaning schedule to avoid this problem.

There would be a need to get the lubrication system flushed right before you think of getting the engine reassembled. Ignoring such action would leave the bearing in bad shape. Look out for dirt or foreign particles that may get trapped between the engine bearing back and housing.

Debris creates a raised area in the engine bearing, causing it to have close contact with the crank journal. So, you should try to get rid of all the dirt when cleaning. When reinstalling engine bearings, make sure you do it on clean surfaces.

Lack of Lubrication

Lubrication is vital for the crankcase. Insufficient lubrication causes the bearing faces to seize. This causes the entire engine to fail, and the car will not function. Therefore, always ensure that the bearings are well lubricated to avoid metal-to-metal contact.

Lack of adequate oil may initially affect one bearing, but eventually, all the beatings will be affected. One way of knowing that such an issue exists is by taking a proper look at the metal of the bearing. If you notice a shining surface, then you need to add a lubricant.

Also, look out for malfunctioning oil pumps, blocked engine passages, and oil seal failures for further diagnosis. It will also help if you check out any improper bearing installation/selection and fuel dilution/aeration caused by an overfilled crankshaft.

Bearing Crush

The crush is the additional material you find extending above the bearing housing when you set the bearing halves in place. It helps hold the bearing’s outer diameter against the housing assembly with the specific assembly torque.

With increased surface contact with the housing bore, the crush minimizes the bearing’s movement. As this happens, there is heat transfer, and excessive crush may reduce the engine consumption as it files down the cap.

Improper Assembly

The installation of the engine bearings goes a long way, as an improper assembly could cause the bearing to fail. In most cases, the journal will not receive lubrication if a half bearing lacking a hole is improperly “placed”.

I am sure you remember the issues that result from oil starvation, right? So, it would help to avoid such problems. Similarly, if you install the rod/main bearing cap incorrectly, there will be a crankshaft bearing failure.

How to Prevent Engine Bearing Failure?

The engine bearing has a substantial service life, and various factors may cause it to wear sooner. It seems pretty imperative to get an accurate diagnosis on how to fix a failing bearing. This helps prevent the bearing from facing further problems and reduces cost.

By now, you should know that the bearing would fail “prematurely” if there is no proper maintenance. Thus, when such a thing occurs, it only means that it happened due to reasons that you could have avoided with great ease.

The major things that could cause many bearing problems (spalling, pitting, unusual wear patterns, corrosion/rust) are operational stress, lubrication, environmental influence, and bearing selection.

Nevertheless, here are some common ways you can prevent an engine-bearing failure. They include:

Adequate Lubrication

Lubricating bearings help to protect contact surfaces from rolling and sliding. It prevents direct metal-to-metal contact. This oil film reduces friction between the surfaces and decreases the occurrence of abrasion.

Lubrication prevents engine bearings from corrosion and rust and prolongs their service life. Always ensure that you use the right grease for lubricating the bearings. Using the wrong type of grease will lead to lubrication failure.

Also, avoid using grease that is already contaminated, for it will cause more problems instead of lubricating. Therefore, endeavor to remove all forms of contamination and foreign objects from the rolling elements.

Dealing with Material Fatigue

Material fatigue often happens when the bearing starts running above the stipulated fatigue limit. It could also happen if there is excessive oil clearance and fuel detonation. Nevertheless, you can easily prevent this problem and increase the service life of the bearing.

One way of doing so is choosing a bearing material with a high load capacity. Another way is replacing or repairing the distorted parts and closing the watch on the oil clearance. Also, use fuel with a high octane number.

Some other helpful tips to prevent the bearing from getting damaged due to various environmental factors include:

  • Using proper sealing techniques and conducting proper cleaning to get out dust and dirt
  • Employing the special type of seals that ends up not scoring the shaft to keep away water
  • Insulating the bearing to handle electrolyte corrosion and current passages may cause sparks and create pitting on bearing surfaces.

Crankshaft Bearing Roll-in (YouTube)

Frequently Asked Questions (FAQs)

Q: What Happens When Engine Bearings Fail?

When the engine bearing fails, there will be no friction between the rotary and stationary parts. In essence, the car will not function properly, and if you continue to drive in such a state, further damage will occur.

One symptom of a bad engine bearing is silver shavings in the engine oil. Soon, you may start noticing some awful noise from the engine due to the rod knock, and the oil pressure will reduce. Again, the belts start wearing out, and the transmission becomes noisy if the thrust bearing face is affected.

Q: What Does a Bad Motor Bearing Sound Like?

When the motor bearing is bad, you will start hearing a clattering noise, which indicates decreased oil pressure. The knocking or clanging sound becomes worse when you drive slowly.

It is quite dangerous to drive with such a problem since the wheel may suddenly stop while driving. Therefore fix the problem as quickly as possible to ensure that the vehicle runs smoothly.

Q: What Causes Big End Bearing to Knock?

Excessive clearance can easily cause the big end bearing to knock since it affects the movement. Normally, those pair of white metal shells found in the oil film afloat do not touch the crank, which is pretty good.

Nevertheless, when the oil pressure is affected, it reduces lubrication or oil starvation, and the bearing starts to hit the crank. With that, the shell begins to spin, which then leads to a total bearing failure.

Q: Can You Replace the Main Bearings Without Removing the Crank?

It is possible to remove the main bearing without removing the crank in some engines. All you need to do is loosen the bolts. However, you have to ensure that the crankshaft does not get overstressed.

On the other hand, you may not be able to achieve this in some engines. It is advisable to remove both the crank and the main bearings if the crankshaft is also damaged. Replacing both components will make the car run better.

Q: How Much Does It Cost to Fix Engine Bearings?

The cost of fixing worn engine bearings depends on the extent of the damages and the cause of bearing failure. However, the parts replacement cost starts from $2,500. This cost may cover the price for the crankshaft, rod and pistons, and cam bearings.

The price also varies from place to place since experts charge differently for the cost of labor. You can check various service stations close to you and see their “worn engine bearings cost.” You can then make your budget based on your findings.

Final Thoughts

Bearings are an essential component of the engine, and it helps in the proper functioning of the car. After using your vehicle for some time, you will start experiencing the bearing wearing out. It is pretty essential to fix the problem before it gets worse. It would therefore help if you were more observant to notice any of the engine-bearing failure symptoms.

The major reasons engine bearing starts failing are inadequate lubrication, debris, bearing crush, and incorrect assembly. This piece contains excellent tips that will help you avoid such issues and improve your vehicle engine bearings’ service life.


Hi There, I am R. Hasan Tito, a mechanic, and owner of this website. My friend and I created this website to share our knowledge, expertise, and experience with our fellow mechanics' community and car users. I am a specialist and certified automotive mechanic (Both Heavy Commercial and Private Cars). I have been working as a mechanic for over fifteen years. I worked for a long time at Global Rebound Automotive companies (Toyota, TATA, BMW, Nissan, TVs, and Others ) as a Mechanic and Mechanics Supervisor.

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