Sealed-for-life bearings: lubrication & maintenance
Sealed-for-life describes a maintenance concept, not infinite bearing or grease life.
On this page8 sections ⌄
What to check
Check if replenishment is intended
Many sealed small bearings are not designed for routine regreasing. Do not lift a seal or inject grease merely because an open bearing would need relubrication.
Identify the failure mode
Noise, heat and drag can arise from fit, contamination, electrical damage or overload as well as lubricant condition. Adding grease cannot reverse damaged raceways.
Keep replacement specifications
Record the original closure, grease and clearance when replacing a sealed bearing. Matching dimensions alone can lose the intended service-life characteristics.
Direct answer
A factory-filled bearing is serviced according to its exact design, not by a general rule that every bearing needs more grease. Seals and shields describe closures; they do not by themselves grant permission to wash out the fill, remove the closure or inject lubricant.
Open, shielded and sealed: choose the correct service question
On a small screen, scroll the table sideways to read every column.
| Observed design | What to establish first | Do not assume |
|---|---|---|
| Open bearing | The housing's grease or oil supply arrangement | That exposed rolling elements require grease rather than oil |
| Metal-shielded bearing / ZZ / 2Z | Exact product's factory fill and replenishment design | That a visible gap is a service port |
| Sealed bearing / 2RS-type description | Complete closure, lubricant and maintenance specification | That the seal should be lifted for routine greasing |
| Housing with a grease fitting | That fitting's intended flow path and discharge | That it feeds every bearing or a sealed cartridge inside |
| Solid or self-lubricating component | Its own material and service instructions | That 'lubrication-free' means unlimited life |
Retain the specification when replacing a factory-filled bearing
Record the complete designation, closure description, clearance and known lubricant specification. A same-size open bearing is not an automatic replacement for a filled sealed version. Likewise, changing the factory lubricant changes a specified part of the product.
If the bearing is noisy, overheated or corroded, inspect the cause and its permitted service scope. Adding oil through a seal is not evidence that damage has been corrected. Lubricant life and rolling-contact fatigue life are different limits; 'sealed for life' is not a promise of indefinite operation.
Reference scope
Manufacturer and technical-institute records reviewed for this page: JTEKT bearing lubrication methods; JTEKT lubricant selection reference; retrieved 2026-10-01 UTC. Values are a dated reference snapshot, not an OEM approval or a substitute for the current technical and safety documents. Original source addresses and retrieval evidence are retained in the private content audit.
Continue with real catalogue data
Preserve the full model, source description and unknown fields when making your shortlist. This reference website does not sell bearings or certify a replacement.
Related questions and tools
Grease vs oil bearing lubrication
Choose the lubrication system before choosing a product name.
Read and apply →Bearing grease viscosity vs NLGI consistency
NLGI grade and base-oil viscosity describe different properties.
Read and apply →Bearing grease compatibility: mixing & changeover
Grease colour does not identify its chemistry or establish compatibility.
Read and apply →Lithium, polyurea & moly bearing greases
A thickener or additive name alone does not define an approved bearing lubricant.
Read and apply →Bearing regreasing quantity & interval
A useful maintenance schedule needs the actual equipment duty, not a universal number of pumps or months.
Read and apply →High-temperature bearing lubrication checklist
Check the whole bearing system at temperature: lubricant, seals, cage, clearance and material stability.
Read and apply →Low-temperature bearing grease & starting torque
A bearing that runs acceptably when warm may struggle at a cold start.
Read and apply →High-speed bearing grease, oil-air & oil-mist checks
High-speed selection combines bearing geometry, lubricant supply, heat and preload.
Read and apply →Water exposure & food-grade bearing lubrication
A food-contact category and water resistance answer different questions.
Read and apply →Cleaning bearings before relubrication
Cleaning is a controlled maintenance operation, not a cure for damaged raceways.
Read and apply →Plain, linear & solid-lubricated bearing maintenance
Not every component in a bearing catalogue follows a rolling-bearing greasing procedure.
Read and apply →Wheel-bearing grease: NLGI ratings, types & product comparison
Choose wheel-bearing grease from the hub specification and service conditions, not its colour or the word 'premium'. Compare documented automotive and marine examples, then check the exact assembly before use.
Read and apply →Reference basis & data limits
Manufacturer terminology is retained in the product records. Technical reference basis: JTEKT Basic Bearing Knowledge (boundary dimensions, tolerance classes and lubrication); NSK Bearing ABCs (lubrication, designations and clearance); NTN technical FAQs (closure codes and component interchange); SKF rolling-bearing selection and maintenance references.
Selection workflows and catalogue grouping are BearingScope editorial aids. Verify the current drawing and application requirements before using a candidate. Missing database information is not converted into an assumed match.