Spun Bearing: Symptoms, and Diagnosis

Spun bearing is among the common problems any car, even lorry encounters anytime because it is the result of a chain of unfortunate events. The spun bearing includes high operating loads, excessive heat, or a loss of lubrication.

Spun bearings are the result of loss of oil pressure, but more contributing factors cause the bearing to seize and spin.

Symptoms of Worn-Out Engine Bearings

Whenever your vehicle has a worn-out main engine bearing or rod bearing, it will begin to display some or all of the common symptoms:

1. Dirt

Bearings can be damaged when dirt particles begin to enter the bearing and its housing, where ideally, there should be a thin layer of lubricating oil. These impurities will cause an abrasive effect on the bearing surface, reducing its clearance with the housing. This problem arises because the engine is not sufficiently clean, or due to dirt in the oil itself.

2. Knocking Noises

Knocking noises is also one of the major symptoms of spun bearing, if you realize that your car engine knocks upon starting the car, there is a chance that your engine bearings are worn and need to be replaced.

3. Incorrect Assembly/Gradual Wear

A spun bearing rod may be caused by the wearing down of the bearing because of improper assembly in the engine. In the long run, a connecting rod or bearings will begin to lose installation, resulting in excess clearance, noise, and damage.

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4. Thin Oil

A spun bearing rod can be caused by using a light oil because it is very low viscosity and it won’t be able to produce enough pressure to separate the bearings from the housing surface. Tiny oil will be more prominent when the engine is warm, as viscosity decreases with temperature.

5. Low Oil Pressure

Low oil pressure is also one of the popular symptoms of spun bearing. Immediately you experience a bearing that is beginning to fail (or has failed), you will notice several signs of decreased oil pressure. This is more evident upon first starting the vehicle. Bad rod bearing will lead to a “check engine oil” light being displayed on your dashboard.

Spun Bearing Diagnosis

It is very important to know the necessary steps when it comes to spun-bearing diagnosing.

To diagnose spun bearing, you need to follow the steps or method below:

1. Plug Wire Removal

One method of identifying the cylinder connected with the faulty rod bearing is to open the car hood and get out all the spark plug wires one by one.

Immediately you need to remove each wire and turn on the engine, now you need to check if the knocking sound persists.

If you realize that the sound has been eliminated, it means that the cylinder from where the plug wire was removed has a faulty bearing on its connecting rod.

2. Visual Inspection

You can also visually inspect the bearings to see if they are damaged or worn-out, out without removing parts of the engine.

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You need to raise the front wheels with a jack and get under the engine, now you need to set the parking brake.

You have to remove the long drainage bolt from the oil pan with a wrench, to drain off its oil. You need to make sure that you keep a catch pan underneath to prevent spills.

If the oil contains metal shavings, then it is an early sign of bearing failure.

You need to remove the oil pan by loosening the bolts surrounding it. Then, remove and inspect the bearings for any damage.

If it is not smooth wear all over, and the bearings show scratches, dirt buildup, discoloration, or pitted surfaces, then you need to replace it.

Does a spun bearing ruin the block?

Spun main bearings are a common disaster, however, if you kill the ignition before it gets critical and the parts hastily leave the crankcase, you will be able to save the block.

Can a spun bearing Be Fixed?

The best case for fixing a spun bearing is replacing the crank, rods, and pistons, but the block is toast so you need to replace a completely new bottom end on your motor.

What causes engine bearings to fail?

Several engine bearing failures are caused by these two factors:

Mixed lubrication with metal-to-metal contact between the bearing and crankshaft surfaces;

Fatigue of the bearing material. Mixed lubrication is one of the causes of engine bearing failures.

What damage can a spun bearing do?

Spun rod bearings are a common failure. A spun rod bearing can tear up the big end bore in the rod, ruin the rod journal on the crankshaft, and it may break the connecting rod. It will be bad news because a broken rod flailing around inside an engine will cause severe damage.

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How much does it cost to fix a spun bearing?

Currently, the average cost that is associated with repairing spun engine rod bearings is about $2,500 (parts plus labor). You’ll need to repair or replace parts like gaskets, cylinder head bolts, engine cooler lines, pistons, crankshafts, and more.

Is Rod knock fixable?

The most effective solution is an engine rebuild where you pull the rods and replace the bearings. The flailing rod damaged the crank journal surface, so you’ll need the crank polished and most likely turned.