Cummins/Onan — Piston/Rod Assembly Installation
Repair & overhaul · piston/connecting rod
From a Cummins/Onan service manual covering: 4.5 MCE, 5.0 MCE, 6.5 MCE. Check it applies to your exact model before use.
Applies to: Cummins/Onan 4.5 MCE, Cummins/Onan 5.0 MCE, Cummins/Onan 6.5 MCE, Cummins/Onan MCE engine
Procedure
- Turn crankshaft until crankpins are at bottom of stroke.
- Lubricate pistons and cylinders and compress rings with a ring compressor.
- Position piston/rod assemblies with connecting rod cap bolt offsets outward.
- Tap pistons down with wood hammer handle until rods seat on crank pins.
- Use Plasti-gage (green code) to check crankpin bearing clearance.
- Lubricate crankpin, attach cap, torque cap bolts to specification.
- Confirm rod moves freely side-to-side; loosen and retap cap if not.
- Crank engine by hand to check all bearings are free.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Cummins/Onan 4.5 MCE →, Cummins/Onan 5.0 MCE →, Cummins/Onan 6.5 MCE →
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.