Yamada 640002 O-Ring 4.9 mm x 1.9 mm, Buna-N for NDP-5 to NDP-25
The Yamada 640002 is the genuine replacement o-ring for NDP-5, NDP-15, NDP-20, NDP-25 and G15 Series pumps. It is a static seal: it sits in a machined groove, gets squeezed when the joint is closed, and that squeeze is the only thing standing between the fluid or the compressed air inside the pump and the outside world.
Elastomer seals fail in a predictable way. Heat and time take the flexibility out of the rubber, the ring takes a permanent set in the shape of its groove, and it stops pushing back against the surfaces it is meant to seal. Chemical attack does the same job faster, swelling the ring until it will not fit the groove or hardening it until it cracks. Either way the first sign is usually a weep rather than a spray, so it pays to look at the joint faces whenever the pump is apart.
Key Features
- Genuine Yamada replacement o-ring
- Material: Buna-N (NBR), 70 durometer
- Nominal size: 4.9 mm x 1.9 mm
- Fits NDP-5, NDP-15, NDP-20, NDP-25 and G15 Series pumps
- One per pump in the assemblies that use it
- Restores a positive seal at the joint without machining or adjustment
Applications
- NDP-5, NDP-15, NDP-20, NDP-25 and G15 Series pumps
- Scheduled rebuilds and seal kit top-ups
- Chasing a weep at a joint face after reassembly
- Replacing a ring that has taken a compression set
- Service after a fluid change that attacked the old elastomer
- Marine, industrial and transfer duty
Specifications
- Brand: Yamada
- Manufacturer: Yamada America
- Manufacturer Part Number: 640002
- Part Type: O-Ring
- Material: Buna-N (NBR), 70 durometer
- Nominal Size: 4.9 mm x 1.9 mm
- Fits: NDP-5, NDP-15, NDP-20, NDP-25 and G15 Series pumps
- Quantity Used: One per pump
- Series Port Size: 3/4 in on the NDP-20 Series
- Condition: New
Frequently Asked Questions
Q: Can I reuse the old O-ring if it looks fine?
It is a false economy. A ring that has been compressed for months has taken a set in the shape of its groove and no longer springs back against the sealing faces. It will often pass a dry test and then weep once the pump is running under pressure.
Q: How do I stop damaging the new ring during assembly?
Use a plastic or brass pick to remove the old one, clean the groove so no grit is trapped under the new ring, and lubricate it lightly with something compatible with the fluid before closing the joint. Most premature failures are assembly damage, not material failure.
Q: Does the durometer number matter?
Yes. Hardness sets how far the ring deflects under a given squeeze. A softer ring in a groove designed for a harder one extrudes into the gap and nibbles away at the edge; a harder one in a soft ring groove may not fill the groove at all.
Q: Should I replace all the O-rings at once?
If the pump is open, yes. They are inexpensive next to the labor of opening the pump, they have all seen the same hours and the same fluid, and replacing one of a set usually means coming back for the others.
Not sure this is the right part? Send us a Picture of the Pump Plate on your pump and the CLR Marine team will confirm the correct o-ring.
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