Cummins/Onan — Thermostats and Seals Replacement
Maintenance · Cooling system
From a Cummins/Onan owner's manual covering: K1800, K2000E, K38, K50, KT38, KTA38, KTA50, KTTA38, KTTA50, KtA38, KtA50, KttA38. Check it applies to your exact model before use.
Applies to: Cummins/Onan K38, Cummins/Onan K50, Cummins/Onan KTA38, Cummins/Onan KTA50, Cummins/Onan K38 and K50 engine
Before you start
- K50 thermostats contain a nitrile rubber seat and must be used on K50 engines.
Procedure
- Remove the capscrews, cover plate, o-ring seals, heat shield (right bank only), thermostat housing and gasket.
- Remove the thermostats and remove the seals from the housing. Discard the seals.
- Check the thermostats for wear; discard if the barrel is worn or fretted.
- Clean all gasket surfaces and bores with solvent or steam.
- Install the seal with the part number positioned up, no more than 0.51 mm [0.020 in] below the top of the cast edge.
- Install the thermostat by pushing on the outer rim.
- Install the gasket, housing, capscrews, heat shield, o-ring seals, cover plate and capscrews.
- Tighten the capscrews to 45 Nm [35 ft-lb].
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Capscrew torque: 45 Nm [35 ft-lb]
- Seal depth: no more than 0.51 mm [0.020 in] below top of cast edge
Full service-parts list: Cummins/Onan K38 →, Cummins/Onan K50 →, Cummins/Onan KTA38 →, Cummins/Onan KTA50 →
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.