The sending unit is located in the front section of the intake manifold in the vicinity of the thermostat.
Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant can be reused unless it is contaminated or is several years old.
See Figure 1
Fig. Fig. 1: The temperature gauge sending unit is located in the front section of the intake manifold, just to the right of the alternator-4.6L engine
Check the appropriate fuse before attempting any other diagnostics.
Disconnect the sending unit electrical harness.
Remove the radiator cap and place a mechanic's thermometer in the coolant.
Using an ohmmeter, check the resistance between the sending unit terminals.
Resistance should be high (74 ohms) with engine coolant cold and low (9.7 ohms) with engine coolant hot.
It is best to check resistance with the engine cool, then start the engine and watch the resistance change as the engine warms.
If resistance does not drop as engine temperature rises, the sending unit is faulty.
REMOVAL & INSTALLATION
Disconnect the negative battery cable.
Drain the cooling system into a suitable container.
See Figures 2 and 3
Fig. Fig. 2: Detach the connector for the temperature sending unit
Fig. Fig. 3: Using a suitable size socket and drive tool, loosen the sending unit
When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.
Detach the electrical connector at the temperature sender/switch.
Remove the temperature sender/switch.
See Figures 4 and 5
Fig. Fig. 4: Remove the sending unit from the intake manifold by carefully unthreading it
Fig. Fig. 5: Install some Teflon® tape on the threads of the new sending unit to help prevent a leak
Apply pipe sealant or Teflon® tape to the threads of the new sender/switch.
Install the temperature sender/switch and connect the electrical connector.
Connect the negative battery cable. Fill the cooling system.
Run the engine and check for leaks.