Lubricant failure (starved, over-filled, mixed or worn-out)

The oil film is gone, and the metal has noticed. Urgency

Not separate ISO modes, but the overheating, seizure, cage and alignment problems that surround them.

What lubricant failure (starved, over-filled, mixed or worn-out) looks like

• Grease that is black, burnt-smelling, hard, lumpy, or milky, or almost none at all
• Heat colours on the races and rollers, and in the worst case metal flow and welding
• Wear that runs through four stages: discolouration, peeling and scoring, roller-end heat damage, then lockup

Rotec AI schematic illustration. It shows the typical pattern and is not a photograph of a real bearing.

How lubricant failure (starved, over-filled, mixed or worn-out) develops

Grease is an oil held in a thickener with additives. Too much of it churns and heats, too little starves the contact, the wrong type or a mix with an incompatible grease softens or hardens, and age and heat wear it out. As the film fails, metal touches metal, heat builds, and the oil oxidises still faster. Oxidation rate doubles for every 10 degrees C of temperature rise.

How fast it progresses: It runs through four levels, from colour change to total lockup. The worse the level, the harder it is to see the original cause, so take samples early.

Causes of lubricant failure (starved, over-filled, mixed or worn-out)

Lubrication

• Over-filling, under-filling, wrong viscosity or additives, mixed greases, worn-out grease, or water in the grease
• Missed relubrication, or the wrong lubrication system for the duty (oil level with splash where circulation is needed)

Environment & sealing

• High operating temperature that accelerates oxidation
• Water, dirt and process fluids that spoil the lubricant

Design & seats

• Seals or housing that trap grease or heat, or block the supply

How to confirm it is lubricant failure (starved, over-filled, mixed or worn-out)

• Compare used grease with a sample of fresh grease: colour, smell, consistency, shiny metal, water
• Do the crackle test on a small sample (see the Lubrication view) if water is suspected
• Check the quantity: weigh what was added against what the bearing needs
• Check the relubrication record for the interval, the grease type and any change of product

How to fix and prevent lubricant failure (starved, over-filled, mixed or worn-out)

• Fill to the quantity the OEM recommends, no more
• Use the specified grease and make sure any switch is compatible (see the compatibility checker)
• Shorten the interval when the bearing runs hot: the grease wears out faster
• Fix the cause of heat or water, then clean the housing and renew the grease

Easily confused with

• Overheating & lubricant breakdown: Overheating is the heat result; lubricant failure is one of its main causes.
• Adhesive wear (smearing & skidding): Smearing is the sliding damage that often follows a thin film.

Catching lubricant failure (starved, over-filled, mixed or worn-out) early

Rising temperature that does not settle, or ultrasonic readings that creep up between relubrications, are the usual early signs of a starved film. Trend both.

Other related modes

Questions about lubricant failure (starved, over-filled, mixed or worn-out)