Cummins/Onan 4MCCK / 605MCCK — Cooling System Testing
Testing & diagnosis
For the Cummins/Onan 4MCCK / 605MCCK, from the Cummins/Onan service manual.
Applies to: Cummins/Onan 605MCCK, Cummins/Onan MCCK, Cummins/Onan MCCK engine
Procedure
- Install a tank of known capacity at the water outlet.
- Run the engine until the thermostat opens.
- Measure the time necessary to fill the tank to obtain flow in gallons per minute.
- If water flow is below 3.5 GPM, check pump operation and inspect passages and water lines for clogging.
- To test for air leaks, insert the cooling system outlet into a tank of water and watch for bubbles.
Tools required
- tank of known capacity Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- If water flow is below 3.5 GPM, check pump operation and inspect the passages and water lines for clogging.
Full service-parts list: Cummins/Onan 605MCCK →, Cummins/Onan MCCK →
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.