GM Chevy Mid-Size Cars 1964-1988 Repair Guide

Sending Units and Sensors

Print

REMOVAL & INSTALLATION



Coolant Temperature

On most vehicles covered in this guide the coolant temperature sensor is located in the left cylinder head between spark plugs. The coolant sensor may also be found on the opposite cylinder head or even in the intake manifold. For most fuel injected vehicles the coolant sensor is threaded into the front of the intake manifold.

  1. Disconnect the negative battery cable.
  2.  
  3. Drain the engine cooling system to a level below the sensor.
  4.  
  5. Disengage the sensor connector.
  6.  
  7. Using a special sensor tool or a 12-point socket, loosen the sensor, then carefully unthread and remove it from the engine.
  8.  

To install:
  1. Thread the sensor into the engine by hand, then tighten using the socket or tool. If a replacement sensor came with instructions use a torque wrench to assure proper tightening.
  2.  
  3. Engage the sensor wiring harness.
  4.  
  5. Connect the negative battery cable.
  6.  
  7. Properly refill the engine cooling system, then run the engine and check for leaks.
  8.  

Oil Pressure

The oil pressure switch is usually threaded into the rear of the intake manifold, just in front of the distributor. If the switch is not there, possible alternate locations include the block, above the starter or the oil filter adapter.

  1. Disconnect the negative battery cable.
  2.  
  3. Disengage the sensor electrical connector.
  4.  
  5. Using a special sensor tool or a 12-point socket, loosen the sensor, then carefully unthread and remove it from the engine.
  6.  

To install:
  1. Thread the sensor into the engine by hand, then tighten using the socket or tool. If a replacement sensor came with instructions use a torque wrench to assure proper tightening.
  2.  
  3. Engage the sensor wiring harness.
  4.  
  5. Connect the negative battery cable, then check for proper sensor operation.
  6.  

Oxygen Sensor

See Figure 1

Beginning in the early 1980s most GM vehicles were equipped with an oxygen sensor for feedback carburetor control. Fuel injected engines, introduced in the later years of this information also required an oxygen sensor for computer air/fuel mixture management. On vehicles so equipped, the oxygen sensor is usually mounted in an exhaust manifold. On some engines, the sensor is mounted at the end of the crossover pipe.

The oxygen sensor must be replaced every 30,000 miles (48,000 km.). The sensor may be difficult to remove when the engine temperature is below 120°F (48°C). Excessive removal force may damage the threads in the exhaust manifold or pipe so follow the removal procedure carefully.

  1. Disconnect the negative battery cable.
  2.  
  3. Locate the oxygen sensor. On the V8 engines, it is normally on the front of the left side exhaust manifold, just above the point where it connects to the exhaust pipe. On the V6 engines, it is on the inside of the exhaust pipe where it bends toward the back of the car.
  4.  

On the V6 engine you may find it necessary to raise the front of the car and remove the oxygen sensor from underneath.



Click image to see an enlarged view

Fig. Fig. 1: Oxygen sensor location and installation

  1. Trace the wires leading from the oxygen sensor back to the first connector and then disengage the sensor harness connector (the connector on the V6 engine is attached to a bracket mounted on the right, rear of the engine block, while the connector in the V8 engine is attached to a bracket mounted on the top of the left side exhaust manifold).
  2.  

The sensor may be extremely difficult to remove when engine temperature is below 120°F (48°C). Be careful as excessive force could damage threads in the exhaust manifold or pipe.

  1. Using a special sensor tool or a socket, loosen the sensor, then carefully unthread and remove it from the engine. If sensor removal is difficult, spray a small amount of commercial heat riser solvent onto the sensor threads and allow it to soak in for at least five minutes, then attempt to loosen and remove the sensor again.
  2.  


CAUTION
Avoid using cleaning solvents of any type on the oxygen sensor. Keep the louvered end free of grease, dirt or other contaminants. Do not drop or roughly handle the sensor. If any of these cautions are ignored, the sensor could be damaged resulting in poor engine performance and excessive exhaust emissions.

To install:
  1. New oxygen sensors will be packaged with an anti-seize lubricant already applied to the threads. If a sensor is removed from the exhaust and is to be reinstalled for any reason, the sensor threads must be coated with a fresh anti-seize compound. Use G.M. anti-seize compound No. 5613695 or the equivalent. This is not a conventional anti-seize paste. The use of a regular compound may electrically insulate the sensor, rendering it inoperative. You must coat the threads with an electrically conductive anti-seize compound.
  2.  
  3. Carefully thread the sensor into the exhaust bore, then tighten to 30 ft. lbs. (41 Nm) using a torque wrench.
  4.  
  5. Engage the sensor harness.
  6.  
  7. Connect the negative battery cable, then start and run the engine to check for proper operation.
  8.  

Knock Sensor

See Figures 2, 3 and 4

  1. Disconnect the negative battery cable.
  2.  
  3. Disengage the wiring harness connector from the knock sensor
  4.  
  5. Loosen and remove the sensor from the engine.
  6.  

To install:
  1. Apply thread sealer (such as soft sealing tape) to the sensor threads.
  2.  
  3. Install the sensor to the engine and tighten.
  4.  
  5. Engage the sensor wiring harness.
  6.  
  7. Connect the negative battery cable and check for proper engine operation.
  8.  



Click image to see an enlarged view

Fig. Fig. 2: Example of a knock sensor



Click image to see an enlarged view

Fig. Fig. 3: Knock sensor installation-late-model carbureted engines



Click image to see an enlarged view

Fig. Fig. 4: Knock sensor installation-fuel injected engines

 
label.common.footer.alt.autozoneLogo