Toyota 90916-03084 Thermostat

Before assuming the thermostat is the cause of a cooling system issue, perform a general check by examining the coolant level, drive belt tension, and temperature gauge or light operation. If the engine takes a long time to warm up or the thermostat is stuck open, replace it with a new one. To further test the thermostat, remove it from the vehicle and suspend it in cold water using a string or wire. Heat the water while observing the thermostat and note the temperature at which it begins to open and when it is fully open. Compare these temperatures to the specifications. If the thermostat fails to open or close as specified, or if it sticks in any position, it should be replaced. To remove the thermostat, disconnect the negative battery cable, drain the coolant, and detach the radiator hose or water inlet pipe. Remove the water inlet pipe on four-cylinder models or unbolt it on V6 models. Remove the fasteners and electrical connectors from the thermostat housing, detach the housing from the engine, and remove the thermostat while noting its installation direction. Clean the sealing surfaces thoroughly. During installation, ensure a new gasket is evenly fitted onto the thermostat, position the thermostat and housing with the jiggle pin at the highest point, tighten the housing fasteners to the specified torque, and reinstall the remaining components in reverse order. Refill the cooling system and, for V6 models, bleed any air from the system. Run the engine, check for leaks, and verify proper operation.

First of all, to check the thermostat for a cooling system problem, start by inspecting the coolant level, drive belt tension, and temperature gauge or light operation. If the thermostat is stuck open, replace the thermostat. If the engine runs hot and the lower radiator hose is not hot, the thermostat is stuck closed, impeding coolant from flowing into the radiator, the thermostat should be replaced. Then, to remove the thermostat, begin by disconnecting the negative cable and draining the coolant, remove the engine drive belt and the alternator, then detach the thermostat housing from the engine. Also, the radiator hose can remain attached unless the housing needs replacement. Next, remove the thermostat, and clean the sealing surfaces thoroughly. Place a new gasket evenly onto the thermostat, ensuring it fits properly all the way around, install the thermostat along with the housing, and secure the housing fasteners to the proper torque. The installation is the reverse order of removal. Finally, refill the cooling system, start the engine, and check for any leaks or irregularities.

Before assuming the thermostat is the cause of a cooling system issue, perform a general check by examining the coolant level, drive belt tension, and temperature gauge or light operation. If the engine takes a long time to warm up or the thermostat is stuck open, replace it with a new one. To further test the thermostat, remove it from the vehicle and suspend it in cold water using a string or wire. Heat the water while observing the thermostat and note the temperature at which it begins to open and when it is fully open. Compare these temperatures to the specifications. If the thermostat fails to open or close as specified, or if it sticks in any position, it should be replaced. To remove the thermostat, disconnect the negative battery cable, drain the coolant, and detach the radiator hose or water inlet pipe. Remove the water inlet pipe on four-cylinder models or unbolt it on V6 models. Remove the fasteners and electrical connectors from the thermostat housing, detach the housing from the engine, and remove the thermostat while noting its installation direction. Clean the sealing surfaces thoroughly. During installation, ensure a new gasket is evenly fitted onto the thermostat, position the thermostat and housing with the jiggle pin at the highest point, tighten the housing fasteners to the specified torque, and reinstall the remaining components in reverse order. Refill the cooling system and, for V6 models, bleed any air from the system. Run the engine, check for leaks, and verify proper operation.

If the engine runs hot and the lower radiator hose is not hot, it indicates that the thermostat is probably stuck closed and should be replaced.

Disconnect the bypass hose and radiator hose from the thermostat housing, then remove the thermostat housing mounting bolts.

If the engine runs hot and the lower radiator hose is not hot, it indicates that the thermostat is probably stuck in the closed position and should be replaced.

The important things to check are the coolant level, drivebelt tension, and temperature gauge or light operation.

90916-A3003 16325-62010 NO