GM Astro/Safari 1985-1996 Repair Guide

Camshaft

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REMOVAL & INSTALLATION



2.5L Engine

See Figures 1 and 2



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Fig. Fig. 1: Aligning the timing gear marks-2.5L engine



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Fig. Fig. 2: Remove the camshaft-to-engine thrust plate bolts through the access hole in the gear-2.5L engine

  1. Disconnect the negative battery cable for safety. Refer to the Pushrod Cover, Removal and Installation and the Valve Lifters, Removal and Installation procedures in this section, then remove the cover, pushrods and the valve lifters from the engine.
  2.  

When removing the pushrods and the valve lifters, be sure to keep them in order for reassembly purposes.

  1. Place a catch pan under the radiator, open the drain cock and drain the cooling system.
  2.  


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 power steering reservoir from the fan shroud, then remove the upper fan shroud and the radiator. Remove the grille, the headlight bezel and the bumper filler panel.
  2.  
  3. Remove the accessory drive belts, the cooling fan and the water pump pulley.
  4.  
  5. If equipped with air conditioning, disconnect the condenser baffles and the condenser attaching bolts, then raise the condenser and block it aside. Be careful not to stress or damage the A/C refrigerant lines.
  6.  
  7. Remove the crankshaft drive belt pulley and the damper hub. Remove the timing gear cover-to-engine bolts and the cover.
  8.  
  9. Label and disconnect the distributor electrical connectors, then remove the hold-down bolt and the distributor from the engine. Remove the oil pump driveshaft.
  10.  
  11. Label and disconnect the vacuum lines from the intake manifold and the thermostat housing, then remove the Exhaust Gas Recirculation (EGR) valve from the intake manifold.
  12.  
  13. Remove the camshaft thrust plate-to-engine bolts. While supporting the camshaft (to prevent damaging the bearing or lobe surfaces), remove it from the front of the engine.
  14.  
  15. Inspect the camshaft for scratches, pitting and/or wear on the bearing and lobe surfaces. Check the timing gear teeth for damage.
  16.  

To install:
  1. Lubricate all of the parts with engine oil and install the camshaft carefully so not to damage the cam bearings. Torque the camshaft thrust plate-to-engine bolts to 90 inch lbs. (10 Nm).
  2.  
  3. Connect the vacuum lines to the intake manifold and the thermostat housing, then install the Exhaust Gas Recirculation (EGR) valve to the intake manifold.
  4.  
  5. Install the oil pump driveshaft.
  6.  
  7. Install the distributor, adjust the timing and connect the distributor electrical connectors.
  8.  
  9. Install the timing gear cover-to-engine bolts and the cover. Install the crankshaft drive belt pulley and the damper hub.
  10.  
  11. If equipped with air conditioning, connect the condenser baffles and the condenser.
  12.  
  13. Install the accessory drive belts, the cooling fan and the water pump pulley.
  14.  
  15. Install the power steering reservoir to the fan shroud, then the upper fan shroud, the radiator. Install the grille, the headlight bezel and the bumper filler panel.
  16.  
  17. Connect the negative battery cable. Refer to the Pushrod Cover, Removal and Installation and the Valve Lifters, Removal and Installation procedures in this section, then install the pushrods and the valve lifters to the engine.
  18.  
  19. Refill the engine with coolant, connect the negative battery cable, start the engine and check for leaks.
  20.  

4.3L Engine

See Figures 3 and 4



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Fig. Fig. 3: Using bolts as a handle, pull STRAIGHT back and carefully remove the camshaft from the engine



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Fig. Fig. 4: Exploded view of the camshaft and other cylinder block component mounting-VIN W shown (VIN B, N or Z similar, but without balance shaft)

The following procedure requires the use of a torsional damper puller/installer tool such as GM tool no. J-23523-E (1985-92 models), J-39046 (1993-96 models) or an equivalent.

  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 engine cooling fan.
  2.  
  3. Remove the radiator assembly.
  4.  
  5. Remove the rocker arm covers.
  6.  
  7. Remove the intake manifold.
  8.  
  9. Remove the timing cover.
  10.  
  11. Remove the valve lifters.
  12.  

When removing the pushrods and the valve lifters, be sure to tag, arrange or otherwise keep them in order to assure installation in their original locations. Of course, if the camshaft is being replaced, this would not be necessary for the lifters, since they would have to be replaced as well.

  1. Align the timing marks, then remove the timing chain and camshaft sprocket.
  2.  
  3. Thread two or three, 5 / 16 -18 in. bolts, which are 4-5 in. (100-125mm) long into the camshaft sprocket retaining holes. Using these camshaft bolts as handles, support the camshaft and pull it from the front of the engine block. Pull the shaft STRAIGHT back and from the bearings, while rotating it slightly; be careful not to damage the camshaft bearing or lobe surfaces.
  4.  
  5. Inspect the camshaft for scratches, pitting and/or wear on the bearing and lobe surfaces. Check the timing sprockets teeth and timing chain for damage and/or wear, replace the damaged parts (if necessary).
  6.  

To install:
  1. Before installing the camshaft, coat the lobes and bearings using either a high viscosity oil with zinc (such as GM 12345501) or with a suitable engine pre-lube.
  2.  

GM recommends that whenever a new camshaft and/or a set of new lifters has been installed, that you change the engine oil and filter, and then add GM engine oil supplement 1052367 to the engine oil upon refill.

  1. Using the bolts as handles, carefully slide the camshaft into the engine. Be certain to push the shaft straight inward to help prevent possible damage to the camshaft bearings.
  2.  
  3. Install the timing chain and camshaft sprocket, making sure to align the timing marks.
  4.  

REMEMBER that if the lifters and/or pushrods are not replaced, they must be reinstalled in their original positions.

  1. Install the valve lifters.
  2.  
  3. Install the timing cover.
  4.  
  5. Install the intake manifold.
  6.  
  7. Install the rocker arm covers.
  8.  
  9. Install the radiator assembly.
  10.  
  11. Install the engine cooling fan.
  12.  
  13. If the camshaft was replaced, change the engine oil and filter.
  14.  
  15. Connect the negative battery cable and properly refill the engine cooling system.
  16.  
  17. Run the engine and check for leaks.
  18.  
  19. Check and/or adjust the engine timing, as necessary.
  20.  
  21. Once the engine has cooled sufficiently, install the engine cover to the passenger compartment.
  22.  

INSPECTION



See Figures 5, 6 and 7



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Fig. Fig. 5: Use a dial indicator to measure the camshaft for straightness (camshaft runout)



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Fig. Fig. 6: Subtract measurement B from measurement A (width from height) in order to determine camshaft lobe lift



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Fig. Fig. 7: A dial gauge can be used to measure lobe lift with the camshaft installed

Using solvent, degrease the camshaft and clean out all of the oil holes. Visually inspect the cam lobes and bearing journals for excessive wear. If a lobe is questionable, check all of the lobes as indicated. If a journal or lobe is worn, the camshaft MUST BE reground or replaced.

If a journal is worn, there is a good chance that the bushings are worn and need replacement.

If the lobes and journals appear intact, place the front and rear journals in V-blocks and rest a dial indicator on the center journal. Rotate the camshaft to check the straightness. If deviation exceeds 0.001 in. (0.0254mm), replace the camshaft.

Check the camshaft lobes with a micrometer, by measuring the lobes from the nose to the base and again at 90° (see illustration). The lobe lift is determined by subtracting the second measurement from the first. If all of the exhaust and intake lobes are not identical, the camshaft must be reground or replaced.

Camshaft lobe lift can also be measured with the shaft still installed.

To determine camshaft lobe wear, with the shaft still installed.

  1. Remove the rocker arm covers.
  2.  
  3. Loosen and reposition the rocker arms so the pushrods can be accessed.
  4.  
  5. Mount a dial gauge so the plunger rests on the end of the pushrod (so it will read pushrod movement).
  6.  
  7. Turn the crankshaft slowly in the normal direction of rotation until the lifter is on the base of the camshaft lobe (the pushrod will not be at its lowest point of travel), then zero the gauge.
  8.  
  9. Rotate the crankshaft slowly until the pushrod moves to the fully raised position.
  10.  
  11. Compare the readings for each camshaft lobe (as shown by the dial indicator) with the specifications.
  12.  

Keep in mind that hydraulic lifters can allow for some camshaft lobe height loss. If a camshaft is close, but out of specification, verify that plunger movement is not responsible for the difference before replacing the shaft.

  1. Reposition and install the rocker arms. For details, please refer to the procedure found earlier in this section.
  2.  
  3. Install the rocker arm covers.
  4.  

 
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