Cummins/Onan — Thermostat Replacement
Repair & overhaul · Cooling system
From a Cummins/Onan owner's manual covering: GTA8.3, GTA8.3 CD1, GTAR 3. Check it applies to your exact model before use.
Applies to: Cummins/Onan GTA8.3 engine
Before you start
- Always use the correct thermostat and never operate the engine without a thermostat.
Procedure
- Disconnect the negative battery cable.
- Drain the cooling system to a position lower than the thermostat housing.
- Remove the radiator hose from the outlet connection.
- Remove the drive belt.
- Loosen the lower alternator link capscrews.
- Remove the upper alternator mounting capscrews.
- Lower the alternator.
- Remove the thermostat housing, lifting bracket, thermostat and thermostat seal.
- Clean the gasket surfaces.
- Package the thermostat, housing and lifting bracket; align gasket with capscrew holes and install capscrews finger tight.
- Tighten all capscrews; torque 24 N.m [18 ft-lb].
- Position the alternator and install the mounting capscrews.
- Install the drive belt and check tensioner capscrew torque 43 N.m [32 ft-lb].
- Fill the cooling system, operate the engine and check for leaks.
Specs & values
- Thermostat housing torque 24 N.m [18 ft-lb]
- Alternator larger top capscrew 43 N.m [32 ft-lb]
- Alternator smaller bottom capscrew 24 N.m [18 ft-lb]
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.