Cummins/Onan — Servicing the Crankcase Breather Valve
Maintenance
From a Cummins/Onan owner's manual — check it applies to your exact model before use.
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Before you start
- Avoid crushing the baffle or allowing shreds to fall into the crankcase.
Procedure
- Lift the rubber cap from the breather tube and lift out the valve.
- Soak then wash the valve in kerosene or suitable solvent so the disc will work freely.
- Run the engine and hold the valve assembly in place to prove it opens and closes.
- Replace a faulty valve with a new one.
- If the metal mesh baffle is restricted, lift it out with a hooked wire, clean and reinstall leaving only 2-1/4 inch of empty space in the top of the breather tube.
- Reassemble the valve as illustrated.
Tools required
- Hooked wire Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Leave 2-1/4 inch of empty space in the top of the breather tube
Source: Cummins/Onan owner's 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.