General Motors first produced the Northstar engine in 1991. Although the Northstar was used primarily in the Cadillac line, it was also used in Pontiacs, Buicks and Oldsmobiles. The Northstar engine features a single temperature sensor, sometimes referred to as a “sending unit.” The sensor relays the temperature of the engine coolant to the instrument panel. Fortunately, changing the sending unit is fairly straightforward.
Drain the radiator coolant into a container by removing the bolt at the base of the radiator with a wrench.
Pull the electrical harness off of the sensor. The sensor is located on the passenger’s side of the front of the engine and faces the back of the radiator.
Remove the sensor with a deep-set socket wrench.
Coat the threads of the new sensor with General Motors gasket sealing compound, part number 1050805.
Tighten the new sensor to 15 ft.-lbs. of torque with a torque wrench.
Connect the electrical harness to the sensor.
Tighten the radiator’s drain bolt with a wrench then fill the radiator with the drained coolant.
