1999 Ford Expedition: Bad Coolant Temperature Sensor

In 1997, Ford eliminated the boxy looking Bronco and released the sleeker looking Expedition. Just as its predecessor, the Bronco, Ford based the Expedition on its F-series pickups. The 1999 Expedition had two engines available: a 240-horsepower, 4.6-liter V-8 and a 260-horsepower, 5.4-liter V-8. Both engines used a small sensor -- the coolant temperature sensor -- to read the temperature of the coolant and relay the information to the temperature gauge and the cooling fan system. Replacing the 1999 Expedition's coolant temperature sensor is a straightforward task, as Ford positioned it in an easily accessed area.

Instructions

1

Open the Expedition's hood and find the coolant temperature sensor on the intake manifold, to the right of the alternator. Slide a drain pan under the engine, below the coolant temperature sensor.

2

Allow the Expedition's engine to cool until it is cool to the touch. Remove the radiator cap to relieve any residual pressure in the cooling system.

3

Press the locking button on the coolant temperature sensor wiring harness and pull the harness from the sensor. Remove the coolant sensor with a ratchet and deep well socket. A small amount of coolant may seep from the hole that the temperature sensor was in.

4

Apply a thin coat of thread sealer on the coolant sensor. Allow the sealer to dry for the amount of time prescribed by the thread sealer's instructions. Hand-tighten the coolant sensor into the top of the engine.

5

Tighten the coolant temperature sensor to 10 to 14 foot-pounds, using a torque wrench and deep-well socket. Press the wiring harness back onto the coolant temperature sensor.

6

Start the engine and allow it to reach operating temperature -- roughly halfway up the Expedition's temperature gauge. Add 50-50 premixed ethylene glycol-based (green) coolant to the radiator until the level reaches the base of the radiator filler neck, if needed.

7

Take the drain pan to a used automotive fluid recycling center, if the engine lost any fluid while removing the sensor.