5.7L ENGINE
The thermostat on the 5.7L gas powered engine is located behind the thermostat housing at the front of the intake manifold (Scheme 24)
Scheme 24
The thermostat is a wax pellet driven, reverse poppet choke type.
Coolant leakage into the pellet container will cause the thermostat to fail in the open position. Thermostats very rarely stick. Do not attempt to free a thermostat with a prying device.
The same thermostat is used for winter and summer seasons. An engine should not be operated without a thermostat, except for servicing or testing. Operating without a thermostat causes longer engine warmup time, unreliable warmup performance, increased exhaust emissions and crankcase condensation that can result in sludge formation.
The thermostat of the 5.9L diesel engine is located in the front of the cylinder head, underneath the thermostat housing (Scheme 25)
Scheme 25
The same thermostat is used for winter and summer seasons. An engine should not be operated without a thermostat, except for servicing or testing. Operating without a thermostat will cause overheating.
The wax pellet is located in a sealed container at the spring end of the thermostat. When heated, the pellet expands, overcoming closing spring tension and water pump pressure to force the valve to open.