Cummins/Onan — Removing and Installing the Heat Exchanger
Repair & overhaul
From a Cummins/Onan owner's manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MDDC, John Deere 4045TFM engine, John Deere 6068TFM engine
Before you start
- Disconnect negative battery cable before working on set.
- Engine components can be hot.
Procedure
- Remove rear doors and top and end panels if equipped.
- Have towels and containers ready to catch raw water.
- Drain enough coolant so it will not spill when heat exchanger is withdrawn.
- Disconnect raw water flow switch connector on front end cap.
- Disconnect raw water hoses from front and rear end caps.
- Remove heat exchanger.
- Lubricate the 4 O-rings (2 each end) with multi-purpose grease.
- Install small O-rings in bore groove and larger O-rings in face groove.
- Install rear end cap with 6 mm (1/4 inch) gap; ensure hose barb points correctly.
- Install front end cap with heat exchanger seated in bore; ensure hose barb points correctly.
- Evenly tighten front end cap screws until cap touches housing.
- Evenly tighten rear end cap screws until cap touches housing.
- Tighten end cap mounting screws to 24 N-m (18 ft-lb).
- Reconnect hoses and switch connector.
Tools required
- Wrenches Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Tighten end cap mounting screws to 24 N-m (18 ft-lb)
Full service-parts list: Cummins/Onan MDDC →, John Deere 4045TFM engine →
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.