MeridexionSealing parts are the cheapest items in an overhaul and the most likely to stop one. A joint that weeps on pressure test means opening the job again, and the cost is not the gasket, it is the waiting. Buying sealing per unit, as a kit, is the habit that avoids it.
A parts list drawn up at the last minute always misses the consumables.
The four specifications that matter
The comparison, in one table:
| Specification | Why it matters | Typical values |
|---|---|---|
| Dimensions | Fit and compression | ID, OD, cross-section — or the original part number |
| Material | Resistance to oil, fuel, water, heat | NBR, FKM/Viton, EPDM, PTFE, graphite, spiral-wound |
| Hardness | Sealing force versus deformation | 70-90 Shore A for O-rings |
| Temperature / pressure rating | Service life at operating conditions | Match to the specific location, not to the engine generally |
Material selection by location
- NBR (nitrile) — general purpose, good with mineral oil and diesel, limited high-temperature resistance.
- FKM (Viton) — high temperature and chemical resistance; used in exhaust and fuel-adjacent locations.
- EPDM — water and steam service; not suitable for oil.
- PTFE — chemically inert, used for aggressive media and low-friction seals.
- Graphite / spiral-wound — high-temperature flanged joints such as exhaust and steam lines.
Using NBR where FKM was specified is the most common substitution error: it fits, seals initially, then hardens and leaks within weeks at elevated temperature.
Why kits are usually the right unit of purchase
When a joint is opened, every seal in it is disturbed. Reusing an O-ring that has taken a compression set is a false economy. Overhaul kits are assembled per unit — per cylinder, per pump, per cooler — so that everything needed for reassembly arrives together rather than in three separate orders.
Kits are listed under gaskets, O-rings and sealing kits.
Storage matters
Elastomers age. Seals stored in sunlight, near ozone sources such as electric motors, or in a hot store will harden before use. Keep them in sealed bags, dark and cool, and respect the shelf life on the packet — typically five years for NBR, longer for FKM.
What we need from you
- Engine or equipment make, model and serial number
- Original part number, or dimensions with a photo of the joint
- Material and hardness if known — say so if it is not
- Medium and operating temperature at that location
- Whether individual seals or a complete overhaul kit
- Quantity per engine and number of units being opened
Seals are also a sensible item to hold on board: they are small, inexpensive, and a missing O-ring can stop a repair. See what to keep as spares.
In short: The expensive version of this mistake involves a crane and a surveyor, and most of the rest is common sense.
Get this sourced
Send what you have – part number, drawing, or a photo. We confirm the specification before we quote, not after.
Common questions
Can I use a standard O-ring instead of the OEM one?
Only if dimensions, material and hardness all match. A dimensionally identical O-ring in the wrong material will seal initially and fail at temperature, which is worse than a visible leak.
How long can gaskets and O-rings be stored?
Typically up to five years for NBR and longer for FKM, if stored sealed, dark and cool, away from ozone sources. Age-hardened seals should not be fitted.
Why do cylinder head gaskets fail repeatedly?
Usually because the joint face is not flat, the correct torque sequence was not followed, or the gasket material is not rated for the temperature and pressure at that location. Replacing the gasket without checking the face gives the same result.