Cummins/Onan GTA38 / GTA50 — Thermostat Remove and Install
Repair & overhaul · Cooling system
For the Cummins/Onan GTA38 / GTA50, from the Cummins/Onan owner's manual.
Applies to: Cummins/Onan GTA38 engine, Cummins/Onan GTA50 engine
Before you start
- GTA50 must use the K50 thermostat with vulcanized nitrile rubber seat.
Procedure
- Disconnect the negative battery cable.
- Drain cooling system to just below the thermostat housing.
- Remove both upper radiator hoses from the thermostat housing.
- Remove the twelve cap-screws; remove thermostat housing and gasket.
- Remove the thermostats and seals.
- Clean and inspect housing for cracks, pitting or damage.
- Check thermostat operation; install seal with part number up.
- Install seal with mallet and driver 3375411 (max 0.51 mm below cast edge).
- Install thermostat by pushing on the outer rim.
- Install new gasket, housing and cap-screws; torque 45 Nm [35 ft-lb].
- Install upper radiator hoses; tighten clamps to 6 Nm [50 in-lb].
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Housing cap-screws 45 Nm [35 ft-lb]
- Hose clamps 6 Nm [50 in-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.