GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual

Exhaust Manifold

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CAUTION
ALWAYS use extreme caution when working around the exhaust system. Make sure the engine has had time to thoroughly cool or personal injury from exhaust system burns may occur. Also, be sure to wear safety goggles when working on exhaust parts and they are likely to rust and loose particle will be falling from them during the procedure.

REMOVAL & INSTALLATION



See Figures 1, 2 and 3

1.9L Engine
  1. Disconnect the negative battery cable, then remove the air cleaner assembly and hot air hose.
  2.  
  3. Raise and support the front of the vehicle safely using jackstands.
  4.  
  5. Disconnect the exhaust pipe and the EGR pipe from the exhaust manifold, then lower the vehicle.
  6.  
  7. If equipped with an A/C compressor or a P/S pump, remove the drive belt(s), the compressor/pump (move them aside) and the mounting brackets.
  8.  
  9. Remove the exhaust manifold shield and the heat stove (if equipped).
  10.  
  11. Remove the exhaust manifold-to-cylinder head nuts, then remove the manifold from the engine.
  12.  

To install:
  1. Using a putty knife, clean the gasket mounting surfaces. Inspect the exhaust manifold for distortion, cracks or damage; replace it, if necessary.
  2.  
  3. Install the exhaust manifold to the engine using a new gasket, then tighten the exhaust manifold-to-cylinder head nuts to 16 ft. lbs. (22 Nm). Tighten the nuts gradually using a sequence, starting with the center and working outwards.
  4.  
  5. Install the remaining components in the reverse order of removal, then remove the jackstands and carefully lower the truck.
  6.  
  7. Install the air cleaner and hot air hoses, then connect the negative battery cable.
  8.  



Click image to see an enlarged view

Fig. Fig. 1: Unbolt the exhaust pipe from the rear of the manifold



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Fig. Fig. 2: Loosen and remove the manifold-to-cylinder head retainers (2.8L shown)



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Fig. Fig. 3: Remove the exhaust manifold from the side of the cylinder head

2.0L Engine

See Figure 4

  1. Disconnect the negative battery cable and remove the air cleaner assembly.
  2.  
  3. Raise and support the front of the vehicle safely using jackstands.
  4.  
  5. Disconnect the exhaust pipe from the exhaust manifold.
  6.  
  7. If equipped with an air injection reaction (AIR) system, remove the AIR hose, the AIR pipe bracket bolt and the dipstick tube bracket.
  8.  



Click image to see an enlarged view

Fig. Fig. 4: Exhaust manifold mounting-2.0L engine

  1. Remove the fuel vapor canister harness (steel) pipes.
  2.  
  3. Remove the exhaust manifold-to-cylinder head bolts and the manifold from the engine.
  4.  

To install:
  1. Using a putty knife, clean the gasket mounting surfaces. Inspect the exhaust manifold for distortion, cracks or damage; replace it, if necessary.
  2.  
  3. Install the exhaust manifold to the engine using a new gasket, then tighten the exhaust manifold-to-cylinder head bolts to 26 ft. lbs. (35 Nm). Tighten the fasteners gradually in a sequence, starting at the center and working outwards.
  4.  

2.2L Diesel Engine
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner and the PCV valve.
  4.  
  5. Disconnect the exhaust pipe from the exhaust manifold at the flange.
  6.  
  7. Remove the exhaust manifold-to-cylinder head nuts and the exhaust manifold from the engine.
  8.  

To install:

In order to replace the gasket, it will be necessary to remove the intake manifold as well.

  1. If not done already, loosen and remove the intake manifold.
  2.  
  3. Using a putty knife, clean the gasket mounting surfaces.
  4.  
  5. Inspect the manifold for cracks, damage or distortion; if necessary, replace the intake or exhaust manifold.
  6.  
  7. Using a new gasket, install the intake and exhaust manifolds onto the cylinder head. Torque the manifold-to-cylinder head nuts/bolts to 10-17 ft. lbs. (14-23 Nm) starting from the center and working outward.
  8.  
  9. Connect the exhaust pipe to the manifold at the flange.
  10.  
  11. Install the PCV valve and the air cleaner.
  12.  
  13. Connect the negative battery cable.
  14.  

2.5L Engine

See Figure 5

The exhaust manifold is located on the left-side of the engine.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner and heat stove pipe.
  4.  
  5. Remove the A/C compressor (if equipped), drive belt, and the rear adjusting bracket (if used). Lay the compressor aside in the engine compartment.
  6.  



Click image to see an enlarged view

Fig. Fig. 5: Exhaust manifold installation-2.5L engine

  1. Remove the dipstick tube and bracket.
  2.  
  3. Disconnect the exhaust pipe from the exhaust manifold.
  4.  
  5. Disengage the electrical connector from the oxygen sensor.
  6.  
  7. Remove the exhaust manifold-to-engine bolts/washers and the manifold from the engine.
  8.  

To install:
  1. Using a putty knife, clean the gasket mounting surfaces.
  2.  
  3. Install the manifold to the engine using a new gasket, then tighten the center retainers 36 ft. lbs. (49 Nm) and the outer retainers to 32 ft. lbs. (43 Nm).
  4.  
  5. Engage the oxygen sensor electrical connector, then connect and secure the exhaust pipe to the manifold.
  6.  
  7. Install the dipstick tube and bracket, then reposition and install the A/C compressor (if equipped), rear adjusting bracket (if used) and the drive belt.
  8.  
  9. Install the air cleaner and the heat stove pipe.
  10.  
  11. Connect the negative battery cable.
  12.  

2.8L Engine

See Figure 6

LEFT-SIDE
  1. Disconnect the negative battery cable, then raise and support the front of the vehicle safely using jackstands.
  2.  
  3. Disconnect the exhaust pipe from the exhaust manifold.
  4.  
  5. Remove the rear exhaust manifold-to-cylinder head bolts, then if necessary for underhood access, remove the jackstands and lower the vehicle.
  6.  
  7. If necessary, disconnect the air management hoses and wiring.
  8.  
  9. If applicable, disconnect the heat stove tube.
  10.  
  11. If equipped, remove the P/S pump and bracket; DO NOT disconnect the power steering hoses, instead reposition the pump with the hoses attached.
  12.  
  13. Remove the remaining exhaust manifold-to-cylinder head bolts, then remove the manifold from the engine.
  14.  

To install:
  1. Using a putty knife, clean the gasket mounting surfaces. Inspect the exhaust manifold for distortion, cracks or damage; replace if necessary.
  2.  
  3. Install the exhaust manifold to the cylinder using a new gasket, then tighten the exhaust manifold-to-cylinder head bolts to 25 ft. lbs. (34 Nm) using a circular pattern, working from the center to the outer ends.
  4.  
  5. If equipped, reposition and secure the P/S pump and bracket
  6.  
  7. If applicable, connect the heat stove tube.
  8.  
  9. If necessary, reconnect the air management hoses and wiring.
  10.  
  11. If lowered earlier for underhood access, raise and support the front of the truck safely using jackstands.
  12.  
  13. Connect the exhaust pipe to the manifold.
  14.  
  15. Remove the jackstands and carefully lower the vehicle, then connect the negative battery cable.
  16.  



Click image to see an enlarged view

Fig. Fig. 6: Exhaust manifold installation-2.8L engine

RIGHT-SIDE
  1. Disconnect the negative battery cable, then raise and support the front of the vehicle safely using jackstands.
  2.  
  3. Disconnect the exhaust pipe from the exhaust manifold.
  4.  
  5. Remove the rear exhaust manifold-to-cylinder head bolts, then if necessary for underhood access, remove the jackstands and lower the vehicle.
  6.  
  7. Remove the AIR system diverter valve and heat shield, then remove the AIR system pump and alternator brackets.
  8.  
  9. If necessary, disconnect the air management hoses and wiring.
  10.  
  11. Remove the remaining exhaust manifold-to-cylinder head bolts, then remove the manifold from the engine.
  12.  

To install:
  1. Using a putty knife, clean the gasket mounting surfaces. Inspect the exhaust manifold for distortion, cracks or damage; replace if necessary.
  2.  
  3. Install the exhaust manifold to the cylinder using a new gasket, then tighten the exhaust manifold-to-cylinder head bolts to 25 ft. lbs. (34 Nm) using a circular pattern, working from the center to the outer ends.
  4.  
  5. If necessary, reconnect the air management hoses and wiring.
  6.  
  7. Install the AIR system pump and alternator brackets, then install the AIR system diverter valve and heat shield.
  8.  
  9. If lowered earlier for underhood access, raise and support the front of the truck safely using jackstands.
  10.  
  11. Connect the exhaust pipe to the manifold.
  12.  
  13. Remove the jackstands and carefully lower the vehicle, then connect the negative battery cable.
  14.  

4.3L Engine, Except MFI-Turbo
  1. Disconnect the negative battery cable, then raise and support the front of the vehicle safely using jackstands.
  2.  

It will be easier if the vehicle is only supported to a height where underhood access is still possible, the vehicle may be left in position for the entire procedure. If the vehicle is raised too high for underhood access, it will have to lowered, raised and lowered again during the procedure.

  1. Disconnect the exhaust pipe from the exhaust manifold.
  2.  
  3. If necessary for underhood access, remove the jackstands and lower the vehicle.
  4.  
  5. Tag and disconnect the spark plug wires from the plugs and from the retaining clips.
  6.  
  7. If removing the left side manifold:
    1. Remove the air cleaner with heat stove pipe and cold air intake pipe.
    2.  
    3. Remove the power steering/alternator rear bracket.
    4.  
    5. Check for sufficient clearance between the manifold and the intermediate steering shaft. On some models it will be necessary to disconnect the intermediate shaft from the steering gear in order to reposition the shaft for clearance.
    6.  

  8.  
  9. If necessary when removing the right side manifold, unbolt the A/C compressor and bracket, then position the assembly aside. DO NOT disconnect the lines or allow them to become kinked or otherwise damaged.
  10.  
  11. If necessary for the right side manifold, remove the spark plugs, dipstick tube and wiring.
  12.  
  13. Unbend the locktangs then remove the exhaust manifold retaining bolts, washers and tab washers. Remove the exhaust manifold, then remove and discard the old gaskets.
  14.  

To install:
  1. Using a putty knife, clean the gasket mounting surfaces. Inspect the exhaust manifold for distortion, cracks or damage; replace if necessary.
  2.  
  3. Install the exhaust manifold to the cylinder using a new gasket, then tighten the exhaust manifold-to-cylinder head bolts to 26 ft. lbs. (36 Nm) on the center exhaust tube and to 20 ft. lbs. (28 Nm) on the front and rear exhaust tubes. Once the bolts are tightened, bend the tabs on the washers back over the heads of all bolts in order to lock them in position.
  4.  
  5. If removed on the right side, install the spark plugs, dipstick tube and wiring.
  6.  
  7. If unbolted, reposition and secure the A/C compressor and bracket assembly.
  8.  
  9. If the left manifold was removed:
    1. If unbolted, reconnect the intermediate shaft to the steering gear.
    2.  
    3. Install the power steering/alternator rear bracket.
    4.  
    5. Install the air cleaner along with the heat stove pipe and cold air intake pipe.
    6.  

  10.  
  11. Connect the spark plug wires to the retainer clips and to the plugs as noted during removal.
  12.  
  13. If lowered for underhood access, raise and support the front of the vehicle again using the jackstands.
  14.  
  15. Connect the exhaust pipe to the manifold.
  16.  
  17. Remove the jackstands and carefully lower the vehicle, then connect the negative battery cable.
  18.  

4.3L MFI-Turbo Engine
LEFT SIDE
  1. Disconnect the negative battery cable, then remove the air cleaner and duct.
  2.  
  3. Remove the turbocharger air inlet elbow, then remove the upper fan shroud.
  4.  
  5. Loosen the fan nuts, then remove the serpentine drive belt. Remove the fan and pulley assembly.
  6.  
  7. Using a suitable pulley remover (such as J-25034-B or equivalent) pull the power steering pump pulley from the pump.
  8.  
  9. Remove the rear brace from the alternator.
  10.  
  11. Raise and support the front of the truck safely using jackstands.
  12.  
  13. Remove the left tire and wheel, then remove the left wheelhouse panel.
  14.  
  15. Disconnect the power steering inlet and outlet hoses from the pump. Immediately plug all openings in order to prevent system contamination or excessive fluid loss.
  16.  
  17. Disconnect the oil filter line bracket from the power steering pump.
  18.  
  19. Disconnect the intermediate shaft.
  20.  
  21. Unbolt the exhaust crossover pipe from the manifold.
  22.  
  23. Remove the power steering pump and rear brace as an assembly from the front bracket.
  24.  
  25. Tag and disconnect the wires from the spark plugs, then remove the plugs from the left cylinder head.
  26.  
  27. Bend back the locktabs, then remove the exhaust manifold bolts, studs, locktabs, washers and heat shields. Remove the exhaust manifold.
  28.  

To install:
  1. Using a putty knife, clean the gasket mounting surfaces. Inspect the exhaust manifold for distortion, cracks or damage; replace if necessary.
  2.  
  3. Install the exhaust manifold to the cylinder using a new gasket, then tighten retainers to 33 ft. lbs. (45 Nm). Once the retainers are tightened, bend the tabs on the washers back over the hex-heads of all bolts/studs in order to lock them in position.
  4.  
  5. Install and tighten the spark plugs, then connect the spark plug wires.
  6.  
  7. Install the power steering pump and rear brace to the front bracket. Tighten the bracket bolts to 37 ft. lbs. (50 Nm) and the rear brace nut to 33 ft. lbs. (45 Nm).
  8.  
  9. Connect the crossover pipe and tighten the retaining nuts to 12 ft. lbs. (16 Nm).
  10.  
  11. Connect the intermediate shaft, then secure the oil filter line bracket to the power steering pump.
  12.  
  13. Remove the plugs, then connect the power steering outlet and inlet hoses to the pump. Tighten the hose fittings to 20 ft. lbs. (27 Nm).
  14.  
  15. Install the left wheelhousing panel, then install the left front tire and wheel assembly.
  16.  
  17. Remove the jackstands and carefully lower the vehicle.
  18.  
  19. Install the rear brace to the alternator and tighten the retaining bolt to 18 ft. lbs. (25 Nm).
  20.  
  21. Install the power steering pump pulley using a suitable installer tool.
  22.  
  23. Install the fan and pulley to the water pump, then install the serpentine drive belt. With the belt installed, tighten the fan and pulley nuts to 18 ft. lbs. (24 Nm).
  24.  
  25. Install the upper fan shroud, then install the turbocharger air inlet elbow.
  26.  
  27. Install the air cleaner and duct.
  28.  
  29. Connect the negative battery cable.
  30.  
  31. Refill the power steering pump and bleed air from the system.
  32.  

RIGHT SIDE
  1. Disconnect the negative battery cable, followed by the positive cable from the battery. Loosen the battery hold-down clamp and remove the battery from the vehicle.
  2.  
  3. Drain the engine cooling system, then remove the battery tray and vacuum tank.
  4.  
  5. Disconnect the turbocharger oil feed hose and the coolant return pipe.
  6.  
  7. Disengage the oxygen sensor connector, then raise and support the vehicle safely using jackstands.
  8.  

It will be easier if the vehicle is only supported to a height where underhood access is still possible, the vehicle may be left in position for the entire procedure. If the vehicle is raised too high for underhood access, it will have to lowered, raised and lowered again during the procedure.

  1. Remove the right front tire and wheel, then remove the right wheelhousing panel.
  2.  
  3. Disconnect the mufflers and tailpipe from the catalytic converter.
  4.  
  5. Remove the catalytic converter support bolts, then if necessary for underhood access, install the wheel, remove the jackstands and carefully lower the vehicle.
  6.  
  7. Disengage the turbocharger solenoid electrical connector and loosen the turbocharger coolant feed line.
  8.  
  9. If the vehicle was lowered, raise and support it safely using jackstands, then remove the turbocharger outlet pipe nuts.
  10.  
  11. Remove the turbocharger outlet pipe support bolt. Move the outlet pipe and catalytic converter away from the turbocharger.
  12.  
  13. Remove the turbocharger oil return pipe from the turbocharger, then remove the turbocharger mounting nuts.
  14.  
  15. Disconnect the coolant feed line from the turbocharger, then remove the turbocharger assembly.
  16.  
  17. Disconnect the exhaust crossover pipe from the manifold.
  18.  
  19. Tag and disconnect the wires from the spark plugs, then remove the plugs from the left cylinder head.
  20.  
  21. Remove the charger air cooler lower supports.
  22.  
  23. Bend back the locktabs, then remove the exhaust manifold bolts, studs, locktabs, washers and heat shields. Remove the exhaust manifold.
  24.  

To install:
  1. Using a putty knife, clean the gasket mounting surfaces. Inspect the exhaust manifold for distortion, cracks or damage; replace if necessary.
  2.  
  3. Install the exhaust manifold to the cylinder using a new gasket, then tighten retainers to 33 ft. lbs. (45 Nm). Once the retainers are tightened, bend the tabs on the washers back over the hex-heads of all bolts/studs in order to lock them in position.
  4.  
  5. Install and tighten the spark plugs, then connect the spark plug wires.
  6.  
  7. Install the charge air cooler lower supports.
  8.  
  9. Connect the exhaust crossover pipe to the manifold, then tighten the retaining nuts to 12 ft. lbs. (16 Nm).
  10.  
  11. Position the turbocharger, then connect the coolant feed pipe and loosely install the bolt.
  12.  
  13. Loosely install the turbocharger mounting nuts followed by the return pipe and bolts. Tighten the coolant feed pipe bolt to 26 ft. lbs. (35 Nm), then mounting nuts to 33 ft. lbs. (45 Nm) and the oil return pipe bolts to 35 inch lbs. (4 Nm).
  14.  
  15. Install the turbocharger outlet pipe and nuts along with the outlet pipe support bolt. Tighten the pipe nuts to 41 ft. lbs. (55 Nm) followed by the support bolt to 22 ft. lbs. (30 Nm).
  16.  
  17. Engage the turbocharger solenoid electrical connector.
  18.  
  19. Loosely install the catalytic converter support bolts, then engage the mufflers and tailpipe to the catalytic converter. Tighten the support bolts to 25 ft. lbs. (34 Nm), then tighten the tailpipe bolts to 24 ft. lbs. (32 Nm).
  20.  
  21. If reinstalled to lower the vehicle earlier, remove the tire and wheel assembly, then install the wheelhousing panel.
  22.  
  23. Install the tire and wheel assembly, then remove the jackstands and carefully lower the vehicle.
  24.  
  25. Engage the oxygen sensor electrical connector.
  26.  
  27. Connect the turbocharger oil feed hose and the coolant return pipe. Tighten the oil hose fitting to 13 ft. lbs. (17 Nm) and the coolant pipe fittings to 16 ft. lbs. (22 Nm).
  28.  
  29. Install the battery tray and vacuum tank.
  30.  
  31. Install the battery and secure using the hold-down clamp.
  32.  
  33. Connect the positive cable, then the negative cable to the battery.
  34.  
  35. Properly refill the engine cooling system.