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Graco 164627 Seal Piston

Genuine OEM Graco 164627 Seal, Piston for Monark Hydra-Clean 5:1 205-638 (Series C). Prevents fluid bypass and stabilizes pump pressure—replace at first signs of leakage or pressure drop.

  • Part No.: 164627
  • Fits: Monark Hydra-Clean 205-638, Series C
  • Location: Displacement pump, Ref. 22
  • Material: Buna-N (nitrile)
  • Related Kit: 206-923 (includes this seal)
  • Function: Seals piston to maintain pressure & reduce bypass

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Function, Fitment & Specs for Graco 164627 Seal, Piston

Compatible Machines

  • 5:1 Ratio Monark Hydra-Clean Pump — Model 205-638, Series C (with polyethylene & rubber packings)

This Seal, Piston sits in the displacement pump of the above Hydra-Clean model and is referenced as item Ref. 22 in the Graco parts diagram.

What is the Graco 164627 Seal, Piston?

The Graco 164627 Seal, Piston is an OEM piston sealing element that prevents fluid bypass around the piston, maintaining pressure and smooth pump operation in compatible Graco Hydra-Clean systems.

Key Details

OEM Part Number 164627
Part Name Seal, Piston
Material (per diagram) Buna-N (nitrile)
Assembly Location Displacement Pump (Ref. 22) of Monark Hydra-Clean 205-638
Included In Repair Kit 206-923 Displacement Pump Repair Kit (kit contains Ref. 22 among other items)

Why this Seal, Piston matters

  • Maintains spray pressure by preventing internal leakage past the piston.
  • Supports consistent flow and extends packing life when kept in good condition.
  • Genuine Graco fit and material for reliable performance.

Fit & Install Notes

  • Confirm your pump is Monark Hydra-Clean 205-638 (Series C) before ordering.
  • Follow Graco procedures: fully depressurize, disassemble the lower, and install the Seal, Piston in the correct orientation.
  • If the piston, rod, or other packings are worn, consider the full 206-923 repair kit.

Frequently Asked Questions

No. The documented fitment is the Monark Hydra-Clean 205-638 (Series C) pump family. For other sprayers, check their parts breakdowns for the exact piston-seal reference.

No. 164627 is a single Seal, Piston. If your lower needs a full refresh, use the appropriate repair kit (for the 205-638 pump this is 206-923).

Noticeable fluid bypass, pressure drop, or erratic cycling often indicates a worn Seal, Piston. Inspect the piston and packings and replace at the first signs of wear.

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