Cummins/Onan — Cooling System Test
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDKA, Cummins/Onan HDKAL/HDKAS engine
Procedure
- Complete a representative installation.
- Use a load bank adjustable to load the genset to its rated full-load.
- Conduct the test where the ambient air temperature is at least 21°C (70°F).
- Measure temperatures with thermocouples not heavier than No. 24 AWG (0.21 mm2).
- Measure engine coolant outlet temperature at the thermostat outlet, bead centered in the coolant.
- Measure ambient air temperature with a shielded thermocouple within 4 feet (1.2 m) of the genset and at the same height.
- Ensure the coolant system is free of air before starting the test.
- Run the genset under full load and record temperatures at 15 minute intervals until they stabilize.
- Calculate LAT = T(max) - T(test) + T(amb).
Tools required
- load bank Amazon
- thermocouples not heavier than No. 24 AWG (0.21 mm2) Amazon
- 2 inch diameter white PVC piping at least 6 inches long (thermocouple shield) Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- LAT goal 40°C (104°F)
- T(max) 107°C (225°F)
- Nominal engine shutdown temperature 110°C (230°F)
- Test ambient at least 21°C (70°F)
Full service-parts list: Cummins/Onan HDKA →
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.