Cummins/Onan — Cooling System Pressure Test
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Before you start
- Do not pressurize the cooling system beyond 138 kPa (20 psi).
Procedure
- Remove the radiator cap from the radiator filler neck.
- Fill the radiator as needed.
- Fit the pressure tester to the radiator neck.
- Pump the cooling system to a maximum of 138 kPa (20 psi) and hold for 2 minutes.
- If the pressure drops within this time, inspect for leaks and repair.
Tools required
- Pressure tester Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Maximum test pressure 138 kPa (20 psi)
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.