Cummins/Onan — T-18A Assembly
Repair & overhaul · Rotor assembly
From a Cummins/Onan service manual covering: ST-50, T-18A, VT-50. Check it applies to your exact model before use.
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Before you start
- Do not damage the compressor turbine wheel when separating housings
- Do not tighten vise too much on shaft; it can bend the shaft
Procedure
- Install new snap rings in each end of center housing.
- Install new bearing washer against turbine-end snap ring, then new bearing secured with outer snap ring.
- Position shroud on center housing and install new piston ring on turbine shoulder.
- Insert turbine and shaft through center housing; install bearing washer and new bearing on compressor end.
- Position thrust washer (grooves out) and install thrust collar over shaft.
- Position new O-ring and align oil feed holes; install new back plate with lockplates and capscrews torqued to 90/110 in-lb [18.1/20.3 N-m].
- Install seal spacer, place impeller on shaft and torque nut per specified sequence.
- Install compressor housing and torque V-band coupling to 40/60 in-lb [4.5/6.8 N-m]; install turbine housing torqued to 100/110 in-lb [11.5/12.5 N-m].
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Back plate capscrews 90/110 in-lb [18.1/20.3 N-m] cast iron
- Impeller nut 125 to 150 in-lb then 35 to 55 in-lb greater than drag torque
- Shaft stretch 0.009 to 0.010 inch [0.23 to 0.25 mm]
- V-band coupling 40/60 in-lb [4.5/6.8 N-m]
- Turbine housing capscrews 100/110 in-lb [11.5/12.5 N-m]
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.