Why do bearings seize?

There is more than one possible cause

• Too little lubricant, blocked oil passages or an incorrect specification
• Prolonged overheating that prevents the oil film from holding up
• Metal particles, dust or water entering the lubrication system
• Incorrect bearing clearance, orientation or fastening
• Component fatigue or misalignment causing uneven loading

Noise is a warning, not a diagnosis

Humming, knocking or scraping can come from bearings, but also from belts, tyres, gears or other parts. Sound alone is difficult to diagnose, and continued driving may make damage worse.

What should you do?

If sudden noise is accompanied by vibration, overheating, an oil-pressure warning or abnormal power delivery, stop safely and arrange an inspection. Do not use thicker oil simply to hide the symptoms.