Diesel Diagnosis: Why Did My Diesel Camshaft Bearings Fail?

Camshafts are responsible for telling both your intake and exhaust valves exactly when to open and close. Camshaft bearings are responsible for keeping everything within very tight tolerances

139-0538-CATERPILLAR-C15-3406E-CAMSHAFT-NEWTo add insult to injury, the repair bill for failed camshaft bearings can be extremely high, depending on how far the damage extends. It is important to figure out the initial root of the problem so that it can be prevented from happening again.

Why do camshaft bearings fail? There are a variety of issues that can cause this. This question, along with many more, will be answered in this article. Read the entire article below!

Shop All Camshaft Bearings!

What Causes Camshaft Journal Bearing Damage?

Uneven Bearing Support

Bearing Wear Caused by Improper Support

Camshaft bearings, much like other moving engine parts, have the unfortunate possibility of metal-on-metal contact. Engineers have designed camshaft bearings to work within very precise tolerances. Over time, these parts can wear down and one of the reasons this happens is due to misaligned bearings. 

When examined closely, the camshaft bearings can show signs of uneven wear. Bearings, regardless of placement or manufacturer, are made to wear evenly. The picture below shows several marks alongside the housing of the bearing, which indicates the wear may have been likely due to misalignment. 

Lack Of Lubrication 

Discolored Journal Due to Lack of Lubrication

Oil is used in engines to provide a thin film of protection between two moving parts. Without lubrication, the parts would wear down much faster and generate tremendous amounts of heat.

For this example, you can see the camshaft has damaged the bearing due to it not having enough oil. Checking your oil regularly will help stop these types of issues from occurring in the first place.  

Poorly installed bearings 

Much like any other engine component, camshaft bearings need to be installed properly. They are engineered to work with clearance oftentimes measuring just thousands of an inch. 

For example, if the oil holes are not aligned properly, the lubricant can make its way to all parts of the camshaft. Therefore, improper lubrication takes place. Over time, this issue will cause both the camshaft and camshaft bearings to wear down much quicker. 

We have several posts that go over camshaft bearings in greater detail as well as proper installation tips. Have a look at it here!

Damaged Camshaft Bearing Improper Install

Excessive Wear

Too much of a good thing is never enough, and this statement is not exempt from camshaft bearings. Whether it's contaminated/low oil, poor installation, or just simply many hardworking miles, parts do wear out. 

There are several things you can do to help prevent camshaft bearings from failing prematurely, but like anything else, they will eventually succumb to the test of time. The best thing an owner-operator can do to prevent premature failure is preventative maintenance. 

Change your oil on time and make sure the right amount of oil is present in the crankcase. On top of that, using the right viscosity is key. Arguably, the most important thing that can be done for someone who’s replaced the camshaft bearings is to make sure that they are installed by a qualified technician. 

Keep in mind that these are just some of the most common examples that cause camshaft bearing journal damage, and there can be many more reasons as to why this happens. 

What Can Be Done To prevent Early Camshaft Bearing Failure?

Preventative maintenance is key to helping camshaft bearings last as long as possible. One such article, published by Brandon Flannery of EngineProfessional.com notes that one of the most common reasons for camshaft bearing failure is due to debris. 

3055146 CUMMINS N14 .010 CONNECTING ROD BEARING NEW HIGHWAY AND HEAVY PARTSMicroscopic particles make their way into the oil, which ultimately causes sludge buildup. The oiling holes on camshaft bearings can become plugged if the oil is contaminated. If you are replacing them, take extra care to get every last bit of sludge out. 

The best way to do this is by blowing compressed air through every nook and cranny while you got the head apart. We know this will be a messy job, but it’s what sets good shops apart from great ones(the same goes for mechanics).

Different cams have different ways they lubricate everything. For example, ISX injector cams are hollow. While it is a great way to reduce rotational mass, it makes a great hiding space for sludge and debris. Much like the principle of a centrifuge, the leftover debris finds its way in there and can end up plugging the oiling holes in the camshaft bearings.

Ultimately, the plugged oiling holes will starve critical components of oil. These include the cam, bearings, and in extreme cases, the head. 

In conclusion, if replacing the camshaft bearings, take extra caution in making sure every corner of the head and cams are spotless. These small details will make a big difference in how long your new camshaft bearings will last. 


Damaged or defective bearings can cause a whole host of issues. Highway & Heavy Parts carries a variety of camshaft bearings for several engines.  If you think you might be experiencing problems due to camshaft bearing damage, Give our ASE-certified techs a call at 844-304-7688 or request a quote online today!



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