The Causes of Thrust Bearing Failure

While it is not common for thrust bearings to fail, their failure can result in catastrophe for an engine. In addition to being a costly and arduous repair effort, thrust bearing failure poses a marked safety threat to operators in the surrounding area. In an engine block, crankshaft thrust bearings are placed into grooves formed by the engine block webbing. The purpose of thrust bearings is to limit the crankshaft’s forward and backward motion by keeping the crankshaft within a set range of motion. By doing this, tolerance within the entire rotating assembly is preserved, maintaining the entire engine’s lifespan.

As the proper function of thrust bearings is integral to the engine as a whole, it’s important to know what causes thrust bearing failure and how to prevent it. There are three main reasons why thrust bearings fail: contaminants and shoddy surface finish, misalignment, or overloading. This blog will explain all three and how to avoid them from causing bearing failure.

The presence of dirt and contaminants is detrimental to all types of bearings, so there’s no question that thrust bearings fall victim to it too. To avoid this, make sure you have an effective maintenance schedule in place and that cleaning is performed regularly with clean cloths and refined oil. Polishing the surface of the thrust bearing, preferably with a machine rather than by hand, is also important. If grinding marks are left on the face of the crankshaft, they can act like wiper blades, removing the bearing’s oil film. A properly finished crankshaft thrust face should have only minuscule polishing marks that go around the thrust surface in a circumferential pattern.

The second common cause of thrust bearing failure is misalignment. Without proper care, cleaning, and maintenance, thrust bearings will inevitably become misaligned and begin grinding against a surface. This will result in sparking and ‘hot spots’ which can damage the overall operation of the engine. It is crucial to maintain a thrust surface set at 90 degrees to the crankshaft centerline. This produces a thrust face that is square to the axis of the main bearing journal. Always verify that thrust bearings have been installed correctly and are properly aligned.

The final cause of thrust bearing failure is overloading. The thrust bearing must be able to absorb forward thrust loads delivered by the transmission, torque converter, or clutch. Overloading is usually caused by operator error or as the result of a distorted crankcase. In either case, overloading will cause unnecessary wear and tear, leading to failure. To avoid this, it’s important not to idle excessively or attempt to modify the engine. If the problem is related to the crankcase, removing additional loads and repairing the bearing with a 90 degree oil routine will help address the problem.

It is critical to take preventative actions against thrust bearing failure. Once failure is discovered, it’s almost always too late. The damage has been done not only to the bearing itself, but the crankshaft as well. Apart from caring for your thrust bearings, it's important to ensure that, for applications as important as an engine, your thrust bearings are of the highest quality. For top-quality thrust bearings and much more, look no further than ASAP Fulfillment.


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