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Home›Repair guides›Cummins/Onan›Water Pump Impeller Inspection

Cummins/Onan — Water Pump Impeller Inspection

Maintenance

From a Cummins/Onan service manual covering: 0.6MAJ, 1.0MAJ, 1.5MAJ, 1.5MAJ-224R, 1.5MAJ-232R, 2.5MAJ. Check it applies to your exact model before use.

Applies to: Cummins/Onan 2.5MAJ

Before you start

  • The neoprene impeller pump should never be run dry.

Procedure

  1. Remove water pump cover and inspect neoprene impeller.
  2. If worn or damaged, install new impeller.
  3. Pump should discharge .56 gal/min at 1800 rpm or .85 gal/min at 3600 rpm when thermostat is open.
  4. Install pump cover air tight to prevent early impeller failure; tighten screws 15 to 17 in-lb.
  5. Prime pump at initial start and beginning of each season.
  6. Use Permatex or approved sealant on all pipe fittings in supply line to water pump.
  7. Check strainer in water suction line for obstructions.

Specs & values

  • .56 gal/min at 1800 rpm
  • .85 gal/min at 3600 rpm
  • 15 to 17 in-lb

Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

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