Cummins/Onan — Cooling System - Flush
Maintenance
From a Cummins/Onan owner's manual covering: QSM11, QSM11 Industrial, QSM11 Marine, QSM1i. Check it applies to your exact model before use.
Applies to: Cummins/Onan QSM1i, Cummins/Onan QSM11 engine
Before you start
- Do not remove pressure cap from a hot engine; coolant is toxic.
Procedure
- Drain the cooling system; do not allow it to dry out.
- Do not remove the coolant filter.
- Add 3.8 liters Fleetguard RESTORE per 38 to 57 liters capacity; fill with clean water.
- Operate engine at normal temperature (at least 85°C) for 1 to 1-1/2 hours.
- Shut off, cool to 50°C and drain.
- Fill with clean water and operate 5 minutes above 85°C.
- Drain; repeat flushing until drained water is clean.
- Fill with 50/50 fully formulated coolant; install pressure cap and check for leaks.
Tools required
- CC-2800 refractometer Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Cummins/Onan QSM1i →
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.