Cummins/Onan 5MDKAU — Replacing the Raw Water Pump Impeller
Repair & overhaul
For the Cummins/Onan 5MDKAU, from the Cummins/Onan service manual.
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Before you start
- Do not lubricate with petroleum products like grease and oil which attack impeller materials
- Close the sea cock before removing the pump
Procedure
- Disconnect negative battery cable, let engine cool and close the sea cock.
- Remove front and top access doors; loosen hose clamps and disconnect hoses.
- Loosen pump mounting bolts, remove the belt and remove the pump.
- Remove the 4 pump cover screws and remove the impeller and O-ring.
- Clean out impeller pieces from heat exchanger and exhaust elbow if vanes broke.
- Install the new impeller, twisting it counter-clockwise into the housing.
- Wet the inside of the pump and impeller with water, soap solution or silicone lubricant.
- Remount pump, reconnect hoses, adjust V-belt tension and reassemble enclosure.
Tools required
- two pliers Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
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.