Crankshaft Failure Symptoms & Sensor Signs

The crankshaft is one of the most vital components in any internal combustion engine. It converts the up-and-down motion of the pistons into the rotational force that turns the wheels, drives pulleys, and keeps the engine running smoothly. When it fails—whether from physical damage or a faulty sensor—the effects can be serious and expensive.

In this guide, we’ll walk through common crankshaft failure symptoms, signs of crankshaft position sensor failure, how to tell them apart, and what steps to take for diagnosis and repair. Whether you’re dealing with crankshaft sensor problems or engine damage itself, this post will help you understand what’s at stake and how to fix it.

What Is a Crankshaft and Why Does It Matter?

The crankshaft is a precision-balanced steel shaft located at the bottom of your engine. It’s connected to the pistons by connecting rods and rotates within the engine block. Each piston’s up-and-down motion causes the crankshaft to spin, which drives the flywheel and transfers energy to the drivetrain.

It’s tightly linked with the camshaft, timing chain or belt, and most critically, the engine crankshaft position sensor. This sensor tracks the crankshaft’s rotational speed and angle to help control ignition and fuel injection timing. Problems with either the crankshaft itself or its sensor can produce overlapping symptoms—understanding the difference is key to accurate diagnosis.

Most Common Crankshaft Failure Symptoms

Mechanical crankshaft damage is rare but severe. It’s more common in high-mileage engines or those with lubrication or bearing issues. Here are the primary symptoms:

Knocking or Clunking Noises from the Engine

One of the first signs of a bad crankshaft is unusual knocking or clunking noises. This happens when crankshaft journals become worn or bearings begin to fail. These noises are typically deeper and more metallic than valve tapping or injector ticks. Ignoring them may lead to catastrophic internal damage.

Loss of Oil Pressure or Oil Warning Light

If the crankshaft bearing clearances become too wide due to wear, oil pressure drops. The engine's oil warning light may come on. Without enough lubrication, the crankshaft and connecting rods overheat and wear faster. Consistently low pressure should trigger immediate inspection.

Metal Shavings in the Oil

When the crankshaft or bearings start to deteriorate, tiny metal particles enter the oil. This is a red flag for internal wear. Checking the oil filter or magnetic drain plug during an oil change can help identify early-stage damage before a full failure occurs.

Engine Vibration or Uneven Operation

A damaged crankshaft may become unbalanced, leading to noticeable engine vibrations—especially under load. These symptoms affect timing accuracy and smoothness. Vibration in sync with engine speed is often tied to crankshaft or harmonic balancer problems.

Engine Won’t Start or Seized Crankshaft

In extreme cases, the crankshaft can seize, locking the engine completely. This is usually due to oil starvation, bearing collapse, or a broken connecting rod. If the engine cranks but doesn't turn over—or doesn’t crank at all—internal teardown is likely required.

Crankshaft Position Sensor: What It Does & Why It Fails

The crankshaft position sensor (often called the CPS sensor) tracks the position and rotation speed of the crankshaft. This data is fed to the engine control module (ECM) to determine precise ignition and injection timing. Without this sensor, most modern engines won’t start.

It’s mounted near the crank pulley, flywheel, or engine block, depending on the engine design. A bad crankshaft sensor can create symptoms that mimic mechanical failure—even though the internal parts are intact.

Reasons for failure include:

How to Diagnose Crankshaft and Sensor Problems

Because the symptoms of crankshaft failure and crankshaft sensor problems can overlap, accurate diagnosis is essential.

Step 1: Scan for Diagnostic Trouble Codes

Use an OBD-II scanner to check for codes related to the crankshaft position sensor. Common ones include:

These point to timing or sensor signal problems and are a good starting point.

Step 2: Inspect the Sensor and Wiring

Locate the crankshaft position sensor and check for oil leaks, cracked housings, or frayed wires. Sensor connectors often corrode or come loose. Ensure it's seated properly and clean.

Step 3: Look for Oil Contamination or Metal Shavings

Drain the oil and check for glittery metal particles or sludge. This helps confirm internal crankshaft wear or bearing failure.

Step 4: Run a Multimeter or Oscilloscope Test

If you suspect a faulty sensor but see no physical damage, test the sensor’s resistance or waveform output with a multimeter or scope. Compare values with factory specs.

Step 5: Manual Crank Rotation

If the engine is locked or stiff, attempt to rotate the crankshaft manually with a breaker bar. Resistance or grinding indicates serious internal failure.

Repair Options for Crankshaft or Sensor Failure

Once diagnosed, here are your most common repair paths:

Crankshaft Sensor Repairs

This is often a quick and affordable fix.

Mechanical Crankshaft Repairs

Engines with high mileage or multiple failures may be better off replaced rather than rebuilt.

Final Thoughts

Distinguishing between crankshaft failure symptoms and crankshaft sensor failure symptoms is critical to avoid unnecessary repairs. Start with diagnostic codes, inspect the sensor, and don’t ignore signs like knocking, low oil pressure, or engine vibration.

With proper diagnosis and timely action, many crankshaft-related problems can be resolved before catastrophic engine damage occurs. For reliable parts and guides, explore The Diesel Store’s inventory or reach out to a qualified technician for a full diagnostic.

FAQ About Crankshaft Failure Symptoms