The Honda 78118-YB3-004 O-Ring (49X5.7) is a genuine OEM sealing component designed for Honda WB20, WD20, WH15, and WH20 water pumps. As a direct OEM replacement, this o-ring is manufactured to Honda's exact dimensional specification — the 49x5.7 sizing is the defining detail, so confirm that measurement matches your pump's application before ordering. Honda supersedes parts at serial number breaks, so cross-reference the part number 78118-YB3-004 against your pump's serial number in the fitment table to ensure this is the correct seal for your unit.
Key Features
- Genuine OEM Sealing Integrity — sourced directly from Honda, this o-ring meets the exact dimensional and material specification required to maintain a leak-free seal in your water pump
- Sized for Correct Fitment — the 49x5.7 variant designation is critical; match this to your pump's service documentation to confirm you have the right seal before installation
- Broad Pump Compatibility — listed for WB20, WD20, WH15, and WH20 Honda water pumps; verify your serial number against the fitment table, as Honda issues parts by serial range
- Leak Prevention — a compromised or worn o-ring allows water or pressure to escape at the sealed joint, reducing pump output and potentially causing water intrusion into areas of the pump not designed to handle it
An o-ring is a precision loop seal that sits in a machined groove and compresses between two mating surfaces to prevent fluid from passing through the joint. In a centrifugal water pump like the WB20, WD20, WH15, and WH20, o-rings are used at key assembly interfaces to maintain internal pressure and keep water from bypassing or leaking at covers, housings, and fittings. When an o-ring hardens, cracks, or takes a permanent set over time, the seal fails — the pump may lose prime, output pressure drops, or water leaks visibly from the joint. Replacing it with the correct OEM part restores the sealed interface to its original condition.
Part Details
| Part Number | 78118-YB3-004 |
|---|---|
| Brand | Honda |
| Part Type | Genuine OEM |
| Description | O-Ring (49X5.7) |
Compatibility & Fitment
| Name | Models | Serial Range |
|---|---|---|
| Water Pump | WB20, WD20, WH15, WH20 | All |
Verify Before You Order
Fitment is machine-number and revision-specific; always confirm your model and serial number against the fitment list.
Why Buy From DHS Equipment
Every part is verified against the manufacturer's part number before it ships, so what you order is what arrives. We carry parts from leading OEM brands and our own DHS Quality Parts line of professional aftermarket components. Need help finding the right part? Our team is available to confirm compatibility whenever you need it. Orders are processed fast to keep your jobs on track. We don't just sell parts. We keep you jobsite ready.
Questions? Contact our team at [email protected] or 866-611-9369 — DHS Equipment is here to help you maintain peak performance.
