Cummins/Onan — Cylinder Head Repair
Repair & overhaul
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Procedure
- Air pressure test head for coolant leaks.
- Fuel line passages test at 80-100 psi.
- Magnetic particle inspect valve seats and injector ports.
- Check valve seat insert security and width.
- Inspect injector sleeves for scratches and seating.
- Inspect valve guides for wear and out-of-round.
- Resurface head if scratched or uneven.
- Replace valve seat inserts if loose or damaged.
Tools required
- ST-1012 hydrostatic tester Amazon
- ST-1166 magnetic crack detector Amazon
- ST-1279 valve seat insert puller 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.