The Honda 78118-YB4-004 O-Ring (71X5.7) is a genuine OEM sealing component designed for WB30 and WD30 water pumps. As a direct Honda OEM part, it is manufactured to the exact dimensions and material specification Honda requires for a leak-free seal. This O-Ring is sized at 71X5.7 — confirm that measurement matches your unit's requirement before ordering. Honda supersedes parts at serial breaks, so verify your pump's serial number against the fitment table to ensure part number 78118-YB4-004 is correct for your machine.
Key Features
- Exact OEM Dimensions — manufactured to Honda's 71X5.7 specification, delivering the sealing surface geometry the pump requires with no gap or distortion.
- Leak-Free Sealing — a worn or deformed O-ring allows water to bypass the sealed joint under pump pressure; this genuine replacement restores that seal cleanly.
- WB30 and WD30 Fitment — sourced directly from Honda and listed for WB30 and WD30 water pumps; match the 71X5.7 size to your pump's sealing groove before installation.
- Serial Number Check Recommended — Honda updates part numbers at production breaks, so cross-reference your pump's serial number with the fitment table to confirm this is the right O-ring for your unit.
An O-ring is a precision loop of sealing material seated in a machined groove, where it is compressed between two mating surfaces to prevent fluid from passing through the joint. In a water pump such as the WB30 and WD30, O-rings maintain watertight connections at critical points in the pump's housing or plumbing circuit, keeping the flow path sealed under operating pressure. When an O-ring degrades, flattens, or takes a set over time, the seal breaks down and water begins to leak at that joint — a small part whose condition has a direct effect on the pump's ability to move water efficiently.
Part Details
| Part Number | 78118-YB4-004 |
|---|---|
| Brand | Honda |
| Part Type | Genuine OEM |
| Description | O-Ring (71X5.7) |
Compatibility & Fitment
| Name | Models | Serial Range |
|---|---|---|
| Water Pump | WB30, WD30 | 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.
