GM Astro/Safari 1985-1996 Repair Guide

Intake Manifold

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REMOVAL & INSTALLATION

2.5L Engine

See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: Exploded view of the intake manifold mounting-early-model 2.5L engines (NOTE that torque values apply ONLY to models retained by bolts and STUDS)

The intake manifold is located on the right side of the cylinder head.


CAUTION
Relieve the pressure on the fuel system before disconnecting any fuel line connection!

  1. From inside the vehicle, remove the engine cover. For details, please refer to General Information & Maintenance of this information.
  2.  
  3. Properly relieve the fuel system pressure, then disconnect the negative battery cable.
  4.  
  5. Place a catch pan under the radiator, open the drain cock and drain the cooling system.
  6.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by 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.

  1. Remove the air cleaner assembly.
  2.  
  3. Label and disengage the wiring harnesses and connectors at the intake manifold.
  4.  
  5. Disconnect the accelerator, TVS, and cruise control cables (as equipped) with brackets.
  6.  
  7. If equipped, remove the cruise control transducer.
  8.  
  9. Disconnect the EGR vacuum line.
  10.  
  11. Remove the emission sensor bracket at the manifold.
  12.  
  13. Tag and disconnect the fuel lines, vacuum lines and wiring from the TBI unit.
  14.  
  15. Disconnect the water pump bypass hose and, if applicable, the heater hoses at the intake manifold.
  16.  
  17. Remove the alternator rear bracket.
  18.  
  19. Tag and disconnect the vacuum hoses and pipes from the intake manifold and the vacuum line clips at the thermostat and manifold.
  20.  
  21. If necessary, tag and disconnect the spark plug wires and the bracket at the manifold. Depending on how the wires are run it may be possible to leave them attached to the spark plugs, but if you disconnect them BE SURE TO LABEL THEM BEFORE REMOVAL.
  22.  
  23. Disconnect the coil wires.
  24.  
  25. Remove the intake manifold bolts, then remove the manifold from the engine.
  26.  

To install:
  1. Using a plastic scraper, clean the gasket mounting surfaces.
  2.  
  3. Install the intake manifold to the engine using a new gasket and carefully thread the retainers.
  4.  
  5. Early-model 2.5L engines use a manifold retained by bolts and studs. For these engines (used through the mid-1980's) tighten the retainers slowly and evenly (starting at the middle and working outward) to 25-37 ft. lbs. (34-50 Nm) using the torque values for each specific fastener as shown in the accompanying illustration. For late-model engines which are retained only by bolts, slowly and evenly tighten all of the retainers to 25 ft. lbs. (34 Nm).
  6.  
  7. Engage the coil wires.
  8.  
  9. Install the spark plug wires and bracket.
  10.  
  11. Connect the vacuum hoses and pipes to the manifold and the vacuum line clips at the thermostat as noted during removal.
  12.  
  13. Install the alternator rear bracket, then connect the coolant bypass hose.
  14.  
  15. If applicable, connect the heater hose at the intake.
  16.  
  17. Connect the fuel lines, vacuum lines and the wiring to the TBI unit.
  18.  
  19. Install the emissions sensor bracket, then connect the EGR valve hose.
  20.  
  21. If equipped, install the cruise control transducer.
  22.  
  23. Connect the accelerator, TVS and cruise control cables (as equipped) with brackets.
  24.  
  25. Engage and secure the wiring harness connectors at the intake, as noted during removal.
  26.  
  27. Install the air cleaner assembly, then connect the negative battery cable.
  28.  
  29. Properly refill the engine cooling system, then check for leaks.
  30.  
  31. Once the engine has cooled sufficiently, install the engine cover to the passenger compartment.
  32.  

4.3L Engine

See Figures 2, 3, 4, 5, 6, 7 and 8



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Fig. Fig. 2: Disconnect all lines, hoses ...



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Fig. Fig. 3: ... and wiring from the intake manifold or from manifold mounted support brackets



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Fig. Fig. 4: Loosen and remove the intake manifold retaining bolts ...



Click image to see an enlarged view

Fig. Fig. 5: ... a ratchet with various extensions will be very helpful for this, then carefully ...



Click image to see an enlarged view

Fig. Fig. 6: ... remove the manifold-NOTE the TBI unit or carb need not be removed on VIN B, N or Z engines



Click image to see an enlarged view

Fig. Fig. 7: Once the manifold has been removed you have free access to the lifter valley



Click image to see an enlarged view

Fig. Fig. 8: To keep debris out of the engine, cover all openings before cleaning the gasket surfaces

VIN B, N AND Z MODELS

See Figures 9, 10 and 11



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Fig. Fig. 9: Exploded view of the 4.3L (VIN B, N and Z) engine intake manifold mounting and RTV sealant application-NOTE that bolt/stud locations will vary based on model year and emission packages



Click image to see an enlarged view

Fig. Fig. 10: Intake manifold bolt torque sequence-1985-90 4.3L (VIN B, N and Z) engines



Click image to see an enlarged view

Fig. Fig. 11: Intake manifold bolt torque sequence-1991-94 4.3L (VIN B or Z) engines

The intake manifold is located between the cylinder heads.


CAUTION
If equipped with a TBI system, relieve the pressure on the fuel system before disconnecting any fuel line connection!

  1. From inside the vehicle, remove the engine cover. For details, please refer to General Information & Maintenance of this information.
  2.  
  3. Properly relieve the fuel system pressure, then disconnect the negative battery cable.
  4.  
  5. Remove the air cleaner assembly and the heat stove tube.
  6.  
  7. Place a catch pan under the radiator, open the drain cock and drain the cooling system.
  8.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by 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.

  1. Matchmark and remove the distributor assembly.
  2.  
  3. If equipped, remove the cruise control transducer.
  4.  
  5. Disconnect the throttle linkage (accelerator, cruise control and the transmission detent cables, as equipped).
  6.  
  7. Remove the air conditioning compressor from the engine and support aside, leaving the refrigerant lines connected. Be sure not to stretch, stress or otherwise damage the A/C lines.
  8.  
  9. Disconnect the engine oil filler tube (at the manifold bracket) and the transmission dipstick/oil filler tube (if equipped) at the manifold or alternator brackets (as applicable).
  10.  
  11. If applicable on early-model vehicles, remove the air conditioning compressor belt idler (if equipped) from the alternator bracket, then the alternator bracket.
  12.  
  13. Tag and disconnect the fuel hoses, the vacuum lines and the electrical connectors from the carburetor or the throttle body, as applicable.
  14.  
  15. On early-model vehicles so equipped, remove the Air Injection Reactor (AIR) hoses and brackets.
  16.  
  17. Disconnect the heater hose and the upper radiator hose.
  18.  
  19. If used, remove the power brake vacuum pipe.
  20.  
  21. If equipped with an external ignition coil, disengage the wiring, then remove the coil.
  22.  
  23. Disconnect the EGR vacuum line.
  24.  
  25. Remove the sensors and bracket from the right side of the engine.
  26.  

When removing the intake manifold retainers, take careful note of the locations for all bolts and studs. The stud locations will vary based on production year and emission packages, but the studs must be installed in their original locations is all engine accessories and controls are to be properly reinstalled.

  1. Remove the intake manifold-to-cylinder head bolts, then carefully lift and remove the intake manifold from the engine.
  2.  
  3. Using a plastic scraper, clean the gasket mounting surfaces, the carbon deposits from the exhaust/EGR passages and the scale/deposits from the coolant passages.
  4.  
  5. Inspect the intake manifold for cracks.
  6.  

To install:
  1. Use new gaskets and RTV sealant (apply a 3 / 16 in. (5mm) bead to the front and rear manifold seals, extend the bead approximately 1 / 2 in. (13mm) up each cylinder head to seal and retain the gaskets). Tighten the intake manifold-to-cylinder head bolts/studs using 2 passes of the proper sequence to 35 ft. lbs. (48 Nm). On 1991-94 vehicles, then tighten bolt 9 to 41 ft. lbs. (56 Nm)
  2.  
  3. Install the emission sensors and bracket.
  4.  
  5. Connect the EGR vacuum line.
  6.  
  7. If equipped with an external ignition coil, install the coil and engage the wiring.
  8.  
  9. If used, install the power brake vacuum pipe.
  10.  
  11. Connect the upper radiator hose and the heater hose.
  12.  
  13. If equipped, install the Air Injection Reactor (AIR) hoses and brackets.
  14.  
  15. Install the fuel hoses, the vacuum lines and the electrical connectors to the carburetor or throttle body, as tagged during removal.
  16.  
  17. If applicable on early-model vehicles, install the air conditioning compressor belt idler (if equipped) to the alternator bracket, then the alternator bracket.
  18.  
  19. Reposition and secure the engine oil filler tube and the transmission dipstick/filler tube (as applicable).
  20.  
  21. If equipped, reposition and secure the A/C compressor.
  22.  
  23. Connect the throttle linkage (accelerator, cruise control and transmission detent cables, as equipped).
  24.  
  25. Align and install the distributor assembly.
  26.  
  27. If equipped, install the cruise control transducer.
  28.  
  29. Install the air cleaner and heat stove tube assembly.
  30.  
  31. Connect the negative battery cable.
  32.  
  33. Properly refill the engine cooling system, then check for leaks.
  34.  
  35. Once the engine has cooled sufficiently, install the engine cover to the passenger compartment.
  36.  

CMFI VIN W

MODELS-1992-95



See Figures 12, 13 and 14



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Fig. Fig. 12: Lower intake manifold bolt torque sequence-1992-95 4.3L (VIN W) engine



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Fig. Fig. 13: Upper intake manifold bolt torque sequence-1992-95 4.3L (VIN W) engine



Click image to see an enlarged view

Fig. Fig. 14: Exploded view of the upper and lower intake manifold assembly-1992-95 4.3L (VIN W) engine

The manufacturer warns that it may be necessary to disconnect the refrigerant lines from the back of the compressor in order to remove the upper intake manifold assembly. If your vehicle is equipped with A/C, before beginning this procedure you must remove determine if this is necessary. If so, take the vehicle to a reputable repair facility and have the A/C system discharged and recovered using a suitable recovery station. ALSO, remember that if you are wrong and later decide that the system must be discharged, you may have to significantly reassemble the motor so the van may be driven to the repair facility.

Unlike previous versions of the 4.3L engine, the VIN W utilizes separate upper and lower intake manifold assemblies. It is possible to remove only the upper manifold assembly for access to fuel injection components. If this is all that is necessary on your vehicle, follow only the steps up to upper intake manifold removal, then skip to that portion of the installation procedure.

  1. Open the hood, then from inside the vehicle, remove the engine cover. For details, please refer to General Information & Maintenance of this information.
  2.  
  3. If your vehicle is equipped with A/C determine if the compressor can be unbolted and repositioned in order to allow upper manifold removal or if the A/C refrigerant lines will have to be removed from the compressor. If you determine they must be removed from the compressor, take the vehicle to a reputable repair facility to have the system discharged and recovered.
  4.  

If only the upper intake manifold is being removed, the fuel system pressure does not need to be released. ALWAYS release the pressure before disconnecting any fuel lines.

  1. Unless only the upper intake manifold is being removed, properly relieve the fuel system pressure.
  2.  
  3. Disconnect the negative battery cable for safety.
  4.  
  5. Unless only the upper intake manifold is being removed, drain the engine cooling system.
  6.  
  7. Remove the air cleaner box and inlet duct.
  8.  
  9. Disengage the wiring harness from the necessary upper intake components including:

    Throttle Position (TP) sensor
     
    Idle Air Control (IAC) motor
     
    Manifold Absolute Pressure (MAP) sensor
     
    Communicator valve
     

  10.  
  11. Disengage the throttle linkage, and the TV linkage if applicable) from the upper intake manifold.
  12.  
  13. Disengage the wiring, then remove the ignition coil.
  14.  
  15. Disconnect the PCV hose at the rear of the upper intake manifold, then tag and disengage the vacuum hoses from both the front and rear of the upper intake.
  16.  
  17. If equipped with A/C, either unbolt and reposition the compressor (you will have to remove the serpentine drive belt first) or disconnect the refrigerant lines from the rear of the compressor. Remember that the A/C refrigerant must be recovered using a suitable recycling/recovery station before the lines can be disconnected.
  18.  
  19. Remove the upper intake manifold bolts and studs, making sure to note or mark the location of all studs to assure proper installation. Remove the upper intake manifold from the engine.
  20.  
  21. Disengage the wiring from the distributor (or HVS as applicable, they both perform the job of "distributing'' secondary ignition voltage to the plugs and are visually very similar) and matchmark the distributor or HVS, then remove the assembly from the engine.
  22.  
  23. Disconnect the upper radiator hose at the thermostat housing and the heater hose at the lower intake manifold.
  24.  
  25. Disconnect the fuel supply and return lines at the rear of the lower intake manifold.
  26.  
  27. Disengage the wiring harness connectors from the necessary lower intake components including:

    Fuel injector
     
    Exhaust Gas Recirculation (EGR) valve
     
    Engine Coolant Temperature (ECT) sensor
     

  28.  
  29. Remove the lower intake manifold retaining bolts, then remove the manifold from the engine.
  30.  
  31. Using a plastic scraper, carefully clean the gasket mounting surfaces. Be sure to inspect the manifold for warpage and/or cracks; if necessary, replace the manifold.
  32.  

To install:
  1. Position the gaskets to the cylinder heads with the port blocking plates to the rear and the "this side up'' stamps facing upward, then apply a 3 / 16 in. (5mm) bead of RTV sealant to the front and rear of the engine block at the block-to-manifold mating surface. Extend the bead 1 / 2 in. (13mm) up each cylinder head to seal and retain the gaskets.
  2.  
  3. Install the lower intake manifold taking care not to disturb the gaskets. Apply sealer such as GM 1052080 or equivalent to the lower manifold retaining bolts, then install and tighten the manifold retainers to 35 ft. lbs. (48 Nm) using the proper torque sequence.
  4.  
  5. Engage the wiring harness to the lower manifold components, including the injector, EGR valve and ECT sensor.
  6.  
  7. Connect the fuel supply and return lines to the rear of the lower intake. Temporarily reconnect the negative battery cable, then pressurize the fuel system (by cycling the ignition without starting the engine) and check for leaks. Disconnect the negative battery cable for safety and continue installation.
  8.  
  9. Connect the heater hose to the lower intake and the upper radiator hose to the thermostat housing.
  10.  
  11. Align the matchmarks and install the distributor or HVS assembly, then engage the wiring.
  12.  
  13. Position a new upper intake manifold gasket on the engine, making sure the green sealing lines are facing upward.
  14.  
  15. Install the upper intake manifold being careful not to pinch the fuel injector wires or fuel lines between the manifolds.
  16.  
  17. Install the manifold retainers, making sure the studs are properly positioned, then tighten them gradually and evenly to 124 inch lbs. (14 Nm).
  18.  
  19. Either reposition and secure the A/C compressor or remove the plugs and reconnect the A/C refrigerant lines to the rear of the compressor.
  20.  
  21. Connect the PCV hose to the rear of the upper intake manifold and the vacuum hoses to both the front and rear of the manifold assembly.
  22.  
  23. Install the ignition coil and engage the wiring.
  24.  
  25. Connect the throttle linkage to the upper intake.
  26.  
  27. Engage the necessary wiring to the upper intake components including the TP sensor, IAC motor, MAP sensor and the communicator valve.
  28.  
  29. Install the air cleaner and air inlet duct.
  30.  
  31. Connect the negative battery cable.
  32.  
  33. Properly refill the engine cooling system, then check for leaks.
  34.  
  35. Once the engine has cooled sufficiently, install the engine cover to the passenger compartment.
  36.  
  37. If the A/C system was discharged, take the van to a reputable repair facility to have the system evacuated, recharged and leak tested. DO NOT WAIT LONG to do this or moisture which entered the system while it was discharged will cause corrosion and internal system damage. ALSO, DO NOT run the compressor until the system has been properly recharged. Depending on how your model is equipped this may mean you CANNOT use the defogger (this automatically turns the compressor on in some vehicles).
  38.  

CSFI VIN W MODELS-1996

See Figures 15, 16, 17 and 18



Click image to see an enlarged view

Fig. Fig. 15: Exploded view of the upper intake manifold and Central Sequential Fuel Injection (CSFI) components



Click image to see an enlarged view

Fig. Fig. 16: Exploded view of the lower intake manifold mounting-1996 4.3L (VIN W) CSFI engines



Click image to see an enlarged view

Fig. Fig. 17: Lower intake manifold-to-block RTV sealer area



Click image to see an enlarged view

Fig. Fig. 18: Lower intake manifold bolt torque sequence-1996 4.3L (VIN W) CSFI engines

Unlike early versions of the 4.3L engine, the VIN W utilizes separate upper and lower intake manifold assemblies. It is possible to remove only the upper manifold assembly for access to fuel injection components. If this is all that is necessary on your vehicle, follow only the steps up to upper intake manifold removal, then skip to that portion of the installation procedure.

  1. From inside the vehicle, remove the engine cover. For details, please refer to General Information & Maintenance of this information.
  2.  

If only the upper intake manifold is being removed, the fuel system pressure does not need to be released. ALWAYS release the pressure before disconnecting any fuel lines.

  1. Unless only the upper intake manifold assembly is being removed, properly relieve the fuel system pressure.
  2.  
  3. Disconnect the negative battery cable for safety.
  4.  
  5. Unless only the upper intake manifold is being removed, drain the engine cooling system.
  6.  
  7. Remove the air cleaner box and inlet duct.
  8.  
  9. Disengage the wiring harness from the necessary upper intake components (including brackets), then position the harness aside.
  10.  
  11. Disengage the throttle linkage and cruise control cable (if equipped), along with the bracket from the upper intake manifold.
  12.  
  13. Disconnect the fuel line bracket from the rear of the lower intake manifold.
  14.  
  15. Disconnect the PCV hose at the upper intake manifold.
  16.  
  17. Disengage the wiring, then remove the ignition coil and bracket.
  18.  
  19. Remove the purge solenoid and bracket.
  20.  
  21. Remove the upper intake manifold bolts and studs, making sure to note or mark the location of all studs to assure proper installation. Remove the upper intake manifold from the engine.
  22.  
  23. Matchmark the relationship of the HVS housing and rotor for proper installation, then remove the HVS distributor assembly from the engine.
  24.  
  25. Disconnect the upper radiator hose at the thermostat housing and the heater hose at the lower intake manifold.
  26.  
  27. Remove the EGR valve.
  28.  
  29. Disconnect the coolant bypass hose.
  30.  
  31. Disconnect the fuel supply and return lines at the rear of the lower intake manifold.
  32.  
  33. Disengage the wiring harness connectors and brackets from the necessary lower intake components.
  34.  
  35. Remove the throttle linkage and cable(s) with bracket from the lower intake manifold.
  36.  
  37. Remove the transmission fluid level indicator tube.
  38.  
  39. Remove the EGR tube, clamp and bolt.
  40.  
  41. Remove the PCV valve and vacuum hoses.
  42.  
  43. Remove the air conditioning compressor, bracket and accessory drive bracket. Reposition and support the A/C compressor aside with the refrigerant lines intact.
  44.  
  45. If needed, remove the alternator bracket bolt next to the thermostat housing
  46.  
  47. Remove the lower intake manifold retaining bolts, then remove the manifold from the engine.
  48.  
  49. Using a plastic scraper, carefully clean the gasket mounting surfaces. Be sure to inspect the manifold for warpage and/or cracks; if necessary, replace the manifold.
  50.  

To install:
  1. Position the gaskets to the cylinder head with the port blocking plates to the rear and the "this side up'' stamps facing upward, then apply a 3 / 16 in. (5mm) bead of RTV sealant to the front and rear of the engine block at the block-to-manifold mating surface. Extend the bead 1 / 2 in. (13mm) up each cylinder head to seal and retain the gaskets.
  2.  
  3. Install the lower intake manifold taking care not to disturb the gaskets. Apply sealer such as GM 1052080 or equivalent to the lower manifold retaining bolts, then install and tighten the manifold retainers in 3 passes of the proper sequence.
    1. First, tighten lower manifold bolts to 26 inch lbs. (3 Nm).
    2.  
    3. Then, tighten the bolts to 106 inch lbs. (12 Nm).
    4.  
    5. Finally, tighten the bolts to 11 ft. lbs. (15 Nm).
    6.  

  4.  
  5. Install the alternator bracket bolt, next to the thermostat housing.
  6.  
  7. Connect the coolant bypass hose, then install the EGR valve.
  8.  
  9. Connect the upper radiator hoses at the thermostat housing and the heater hose at the lower manifold.
  10.  
  11. Engage the wiring harness and brackets to the lower manifold components.
  12.  
  13. Connect the fuel supply and return lines at the rear of the lower intake. Temporarily reconnect the negative battery cable, then pressurize the fuel system (by cycling the ignition without starting the engine) and check for leaks. Disconnect the negative battery cable for safety and continue installation.
  14.  
  15. Install the throttle linkage cable(s) and bracket to the lower manifold.
  16.  
  17. Install the transmission fluid level indicator tube.
  18.  
  19. Install the EGR tube, clamp and bolt.
  20.  
  21. Install the PCV valve and connect the vacuum hoses.
  22.  
  23. If equipped, carefully reposition and secure the A/C compressor, bracket and accessory drive bracket.
  24.  
  25. Align the matchmarks and install the HVS distributor assembly, then engage the wiring.
  26.  
  27. Position a new upper intake manifold gasket on the engine.
  28.  
  29. Install the upper intake manifold being careful not to pinch the fuel injector wires or lines between the manifolds.
  30.  
  31. Install the manifold retainers (starting with the 2 corner studs first to help align the 2 halves), making sure the studs are properly positioned, then tighten them using the proper sequence to 83 inch lbs. (10 Nm).
  32.  
  33. Install the purge solenoid and bracket.
  34.  
  35. Install the ignition coil and bracket, then engage the wiring.
  36.  
  37. Connect the PCV hose at the upper intake manifold assembly.
  38.  
  39. Secure the fuel lines to the intake at the rear of the block.
  40.  
  41. Connect the throttle linkage to the upper intake.
  42.  
  43. Engage the necessary wiring and brackets to the upper intake components.
  44.  
  45. Install the air cleaner and air inlet duct.
  46.  
  47. Connect the negative battery cable.
  48.  
  49. Properly refill the engine cooling system and check for leaks.
  50.  
  51. Once the engine has cooled sufficiently, install the engine cover to the passenger compartment.
  52.  

 
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