Mazda Trucks 1994-1998 Repair Guide

Camshafts

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REMOVAL & INSTALLATION



2.3L and 2.5L Engines

See Figure 1

The following procedure covers camshaft removal and installation with the cylinder head on or off the engine. If the cylinder head has been removed, follow Steps 7-9 then skip to Step 12.

  1. Drain the cooling system. Remove the air cleaner assembly and disconnect the negative battery cable.
  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 spark plug wires from the plugs, disconnect the retainer from the valve cover and position the wires out of the way. Disconnect rubber vacuum lines as necessary.
  2.  
  3. Remove all drive belts. Remove the alternator mounting bracket-to-cylinder head mounting bolts, position bracket and alternator out of the way.
  4.  
  5. Disconnect and remove the upper radiator hose. Disconnect the radiator shroud.
  6.  
  7. Remove the fan blades and water pump pulley and fan shroud. Remove cam belt and valve covers.
  8.  
  9. Align engine timing marks at TDC for No. 1 cylinder. Remove cam drive belt.
  10.  
  11. Remove the rocker arms (camshaft followers).
  12.  
  13. Remove the camshaft drive gear and belt guide using a suitable puller. Remove the front oil seal with a sheet metal screw and slide hammer.
  14.  
  15. Remove the camshaft retainer located on the rear mounting stand by unbolting the two bolts.
  16.  
  17. Jack up the front of the vehicle and support on jackstands. Remove the front motor mount bolts. Disconnect the lower radiator hose from the radiator. Disconnect and plug the automatic transmission cooler lines.
  18.  
  19. Position a piece of wood on a floor jack and raise the engine carefully as far as it will go. Place blocks of wood between the engine mounts and crossmember pedestals.
  20.  
  21. Remove the camshaft by carefully withdrawing toward the front of the engine. Caution should be used to prevent damage to cam bearings, lobes and journals.
  22.  
  23. Check the camshaft journals and lobes for wear. Inspect the cam bearings, if worn (unless the proper bearing installing tool is on hand), the cylinder head must be removed for new bearings to be installed by a machine shop.
  24.  



Click image to see an enlarged view

Fig. Fig. 1: Exploded view of the camshaft mounting on the 2.3L engine-2.5L engine similar

  1. Camshaft installation is in the reverse order of service removal procedure. Coat the camshaft with a heavy SF (or better) grade oil before sliding it into the cylinder head. Install a new front seal. Apply a coat of sealer or teflon tape to the cam drive gear bolt before installation. After any procedure requiring removal of the rocker arms, each lash adjuster must be fully collapsed after assembly, then released. This must be done before the camshaft is turned.
  2.  
  3. Refill cooling system. Start engine and check for leaks. Roadtest the vehicle for proper operation.
  4.  

3.0L Engine (B Series Pick-up)

See Figures 2 and 3

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner hoses.
  4.  
  5. Remove the fan and spacer, and shroud.
  6.  
  7. Drain the cooling system. Remove the radiator.
  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. Remove the condenser.
  2.  
  3. Relieve the fuel system pressure.
  4.  
  5. Remove the fuel lines at the fuel supply manifold.
  6.  
  7. Tag and disconnect all vacuum hoses in the way.
  8.  
  9. Tag and disconnect all wires in the way.
  10.  
  11. Remove the engine front cover and water pump.
  12.  
  13. Remove the alternator.
  14.  
  15. Remove the power steering pump and secure it out of the way. DO NOT disconnect the hoses!
  16.  
  17. Remove the air conditioning compressor and secure it out of the way. DO NOT disconnect the hoses!
  18.  
  19. Remove the throttle body.
  20.  
  21. Remove the fuel injection harness.
  22.  
  23. Drain the engine oil into a suitable container and dispose of it properly.
  24.  


CAUTION
The EPA warns that prolonged contact with used engine oil may cause a number of skin disorders, including cancer! You should make every effort to minimize your exposure to used engine oil. Protective gloves should be worn when changing the oil. Wash your hands and any other exposed skin areas as soon as possible after exposure to used engine oil. Soap and water, or waterless hand cleaner should be used.

  1. Turn the engine by hand to 0 BTDC of the power stroke on No. 1 cylinder.
  2.  
  3. Disconnect the spark plug wires from the plugs.
  4.  
  5. If equipped, remove the distributor cap with the spark plug wires as an assembly.
  6.  
  7. If equipped, matchmark the rotor, distributor body and engine. Disconnect the distributor wiring harness and remove the distributor.
  8.  
  9. Remove the valve covers.
  10.  
  11. Remove the intake manifold.
  12.  
  13. Loosen the rocker arm bolts enough to pivot the rocker arms out of the way and remove the pushrods. Identify them for installation. They must be installed in their original positions!
  14.  
  15. Remove the valve lifters. Identify them for installation.
  16.  
  17. Remove the crankshaft pulley/damper.
  18.  
  19. Remove the starter.
  20.  
  21. Remove the oil pan.
  22.  
  23. Turn the engine by hand until the timing marks align at TDC of the power stroke on No.1 piston.
  24.  
  25. Check the camshaft end-play. If excessive, you'll have to replace the thrust plate.
  26.  
  27. Remove the camshaft gear attaching bolt and washer, then slide the gear off the camshaft.
  28.  
  29. Remove the camshaft thrust plate.
  30.  
  31. Carefully slide the camshaft out of the engine block, using caution to avoid any damage to the camshaft bearings.
  32.  

To install:
  1. Oil the camshaft journals and cam lobes with heavy SG engine oil (50W). Install the spacer ring with the chamfered side toward the camshaft, then insert the camshaft key.
  2.  
  3. Install the camshaft in the block, using caution to avoid any damage to the camshaft bearings.
  4.  
  5. Install the thrust plate. Tighten the attaching screws to 84 inch lbs.
  6.  
  7. Rotate the camshaft and crankshaft as necessary to align the timing marks. Install the camshaft gear and chain. Tighten the attaching bolt to 46 ft. lbs. (62 Nm).
  8.  



Click image to see an enlarged view

Fig. Fig. 2: Camshaft installation-3.0L engines



Click image to see an enlarged view

Fig. Fig. 3: Rocker arm positioning-3.0L engines

  1. Coat the tappets with 50W engine oil and place them in their original locations.
  2.  
  3. Apply 50W engine oil to both ends of the pushrods. Install the pushrods in their original locations.
  4.  
  5. Pivot the rocker arms into position. Tighten the fulcrum bolts to 8 ft. lbs. (11 Nm).
  6.  
  7. Rotate the engine until both timing marks are at the tops of their sprockets and aligned. Tighten the following fulcrum bolts to 18 ft. lbs. (24 Nm):

    No.1 intake
     
    No.2 exhaust
     
    No.4 intake
     
    No.5 exhaust
     

  8.  
  9. Rotate the engine until the camshaft timing mark is at the bottom of the sprocket and the crankshaft timing mark is at the top of the sprocket, and both are aligned. Tighten the following fulcrum bolts to 18 ft. lbs. (24 Nm):

    No.1 exhaust
     
    No.2 intake
     
    No.3 intake and exhaust
     
    No.4 exhaust
     
    No.5 intake
     
    No.6 intake and exhaust
     

  10.  
  11. Now, tighten all the bolts to 24 ft. lbs. (33 Nm).
  12.  
  13. Turn the engine by hand to 0 BTDC of the power stroke on No. 1 cylinder.
  14.  
  15. Install the engine front cover and water pump assembly.
  16.  
  17. Install the oil pan.
  18.  
  19. Install the crankshaft damper/pulley.
  20.  
  21. Install the intake manifold and tighten the mounting bolts to the specifications and in the sequence described under Intake Manifold removal and installation.
  22.  
  23. Install the valve covers.
  24.  
  25. Install the injector harness.
  26.  
  27. If equipped, install the distributor.
  28.  
  29. Install the cap and wires.
  30.  
  31. Install the throttle body.
  32.  
  33. Install the alternator.
  34.  
  35. Install the power steering pump.
  36.  
  37. Install the compressor.
  38.  
  39. Connect all wires.
  40.  
  41. Connect all vacuum lines.
  42.  
  43. Install the radiator and condenser.
  44.  
  45. Install the fan and clutch.
  46.  
  47. Install the fuel lines.
  48.  
  49. Install the starter.
  50.  
  51. Refill the cooling system.
  52.  
  53. Replace the oil filter and refill the crankcase with the specified amount of engine oil.
  54.  
  55. Reconnect the battery ground cable.
  56.  
  57. Start the engine and check the ignition timing and idle speed. Adjust if necessary. Run the engine at fast idle and check for coolant, fuel, vacuum or oil leaks.
  58.  

4.0L Engine

See Figures 4 and 5

  1. Disconnect the negative battery cable.
  2.  
  3. Drain the engine oil into a suitable container and dispose of it properly.
  4.  


CAUTION
The EPA warns that prolonged contact with used engine oil may cause a number of skin disorders, including cancer! You should make every effort to minimize your exposure to used engine oil. Protective gloves should be worn when changing the oil. Wash your hands and any other exposed skin areas as soon as possible after exposure to used engine oil. Soap and water, or waterless hand cleaner should be used.

  1. 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 radiator.
  2.  
  3. Remove the condenser.
  4.  
  5. Remove the fan and spacer, and shroud.
  6.  
  7. Remove the air cleaner hoses.
  8.  
  9. Tag and remove the spark plug wires.
  10.  
  11. Remove the EDIS ignition coil and bracket.
  12.  
  13. Remove the crankshaft pulley/damper.
  14.  
  15. Remove the clamp. bolt and oil pump drive from the rear of the block.
  16.  
  17. Remove the alternator.
  18.  
  19. Relieve the fuel system pressure.
  20.  
  21. Remove the fuel lines at the fuel supply manifold.
  22.  
  23. Remove the upper and lower intake manifolds as previously described.
  24.  
  25. Remove the rocker arm covers.
  26.  
  27. Remove the rocker shaft assemblies.
  28.  
  29. Remove the pushrods. Identify them for installation. They must be installed in their original positions!
  30.  
  31. Remove the tappets. Identify them for installation.
  32.  
  33. Remove the oil pan as previously described.
  34.  
  35. Remove the engine front cover and water pump.
  36.  
  37. Place the timing chain tensioner in the retracted position and install the retaining clip.
  38.  
  39. Turn the engine by hand until the timing marks align at TDC of the power stroke on No.1 piston.
  40.  
  41. Check the camshaft end-play. If excessive, you'll have to replace the thrust plate.
  42.  
  43. Remove the camshaft gear attaching bolt and washer, then slide the gear off the camshaft.
  44.  
  45. Remove the camshaft thrust plate.
  46.  
  47. Carefully slide the camshaft out of the engine block, using caution to avoid any damage to the camshaft bearings.
  48.  

To install:
  1. Oil the camshaft journals and cam lobes with a heavy (50W) SG grade (or better) engine oil.
  2.  
  3. Install the camshaft in the block, using caution to avoid any damage to the camshaft bearings.
  4.  
  5. Install the thrust plate. Make sure that it covers the main oil gallery. Tighten the attaching screws to 96 inch lbs. (11 Nm).
  6.  



Click image to see an enlarged view

Fig. Fig. 4: Camshaft installation-4.0L engines



Click image to see an enlarged view

Fig. Fig. 5: Timing mark alignment-4.0L engines

  1. Rotate the camshaft and crankshaft as necessary to align the timing marks. Install the camshaft gear and chain. Tighten the attaching bolt to 50 ft. lbs. (68 Nm).
  2.  
  3. Remove the clip from the chain tensioner.
  4.  
  5. Install the engine front cover and water pump assembly. Refer to the necessary service procedures in this Section.
  6.  
  7. Install the crankshaft damper/pulley.
  8.  
  9. Install the oil pan.
  10.  
  11. Coat the tappets with 50W engine oil and place them in their original locations.
  12.  
  13. Apply 50W engine oil to both ends of the pushrods. Install the pushrods in their original locations.
  14.  
  15. Install the upper and lower intake manifolds.
  16.  
  17. Install the rocker shaft assemblies.
  18.  
  19. Install the valve covers.
  20.  
  21. Install the fan and clutch.
  22.  
  23. Install the fuel lines.
  24.  
  25. Install the oil pump drive.
  26.  
  27. Install the alternator.
  28.  
  29. Install the EDIS coil and plug wires. Coat the inside of each wire boot with silicone lubricant.
  30.  
  31. Install the radiator and condenser.
  32.  
  33. Refill the cooling system.
  34.  
  35. Replace the oil filter and refill the crankcase with the specified amount of engine oil.
  36.  
  37. Reconnect the battery ground cable.
  38.  
  39. Start the engine and check the ignition timing and idle speed. Adjust if necessary. Run the engine at fast idle and check for coolant, fuel, vacuum or oil leaks.
  40.  

2.6L Engine

See Figure 6



Click image to see an enlarged view

Fig. Fig. 6: Camshaft and cylinder head components-2.6L engine

  1. Disconnect the negative battery cable, and drain the cooling system.
  2.  
  3. Remove the rocker cover. Check to ensure the engine is set on TDC. The timing mark on the camshaft sprocket should be 90 degrees to the right, parallel to the top of the cylinder head. Make sure the yellow crankshaft pulley timing mark is aligned with the indicator pin.
  4.  
  5. Remove the seal cover.
  6.  
  7. Mark the position of the distributor rotor in relation to the distributor housing, and the distributor housing in relation to the cylinder head. Remove the distributor. Do not rotate the engine after distributor removal.
  8.  
  9. Hold the crankshaft pulley with a suitable tool and remove the distributor drive gear/camshaft pulley retaining bolt and the drive gear. Remove the upper timing cover assembly.
  10.  
  11. Push the timing chain adjuster sleeve in towards the left, and insert a 2mm diameter x 45mm long pin into the lever hole to hold it in place.
  12.  
  13. Wire the chain to the pulley and remove the pulley from the camshaft. Do not allow the sprocket and chain to fall down into the engine and cause the chain to become disengaged from the crankshaft sprocket.
  14.  
  15. Remove the rocker arm/shaft assembly.
  16.  
  17. Remove the camshaft.
  18.  
  19. Inspect the camshaft for wear and/or damage and replace if necessary.
  20.  

To install:
  1. Apply clean engine oil to the camshaft journals, lobes and bearings. Install the camshaft with the dowel pin facing upwards.
  2.  
  3. Install the rocker arm/shaft assembly and tighten the bolts, in sequence, in 2-3 steps to 14-19 ft. lbs. (19-25 Nm). Make sure the rocker arm shaft spring does not get caught between the shaft and mounting boss during installation.
  4.  
  5. Install the camshaft sprocket and tighten the bolt to 37-44 ft. lbs. (50-60 Nm).
  6.  

Remove all old sealer from the distributor drive gear and apply sealer to the gear face, then seat the gear fully on the camshaft.

  1. Install the distributor drive gear and distributor.
  2.  
  3. Install the seal cover.
  4.  
  5. Coat a new gasket with silicone sealant and install on the rocker arm cover. Install the cover and tighten the bolts to 53-78 inch lbs. (6-9 Nm).
  6.  
  7. Remove the timing chain adjuster sleeve pin. Install the upper timing chain cover.
  8.  
  9. Connect the negative battery cable. Fill and bleed the cooling system.
  10.  
  11. Run the engine and check for leaks and proper operation. Check the idle speed and ignition timing.
  12.  

3.0L Engine (MPV)

See Figure 7



Click image to see an enlarged view

Fig. Fig. 7: Camshaft and cylinder head components-3.0L engine


CAUTION
Fuel injection systems remain under pressure after the engine has been turned OFF. Properly relieve fuel pressure before disconnecting any fuel lines. Failure to do so may result in fire or personal injury. Do not allow fuel spray or fuel vapors to come in contact with a spark or open flame. Keep a dry chemical fire extinguisher nearby. Never store fuel in an open container due to risk of fire or explosion.

  1. Disconnect the negative battery cable.
  2.  
  3. Drain the cooling system.
  4.  
  5. Relieve the fuel system pressure.
  6.  
  7. Remove the PCV valve and blind cover.
  8.  
  9. Remove the cylinder head.
  10.  
  11. If removing the driver's side camshaft, remove the distributor and the distributor spacer.
  12.  
  13. Remove the camshaft sprocket bolt and sprocket.
  14.  
  15. Remove the seal plate. Pry out the camshaft seal, being careful not to damage the seal housing.
  16.  
  17. Remove the rocker arm/shaft assembly.
  18.  
  19. Remove the thrust plate bolts and remove the thrust plate. Slide the camshaft out of the cylinder head. If removing the driver's side camshaft, remove the distributor drive gear.
  20.  
  21. Inspect the camshaft for wear and/or damage and replace if necessary.
  22.  

To install:

If installing the driver's side camshaft, remove all old sealer from the distributor drive gear and apply sealer to the gear face, then seat the gear fully on the camshaft.

  1. Apply clean engine oil to the camshaft journals, lobes and bearings. Install the camshaft and the thrust plate. Tighten the thrust plate to 69-95 inch lbs. (7.8-11.0 Nm).
  2.  
  3. Apply clean engine oil to a new camshaft seal lip and press the seal into the cylinder head, using a seal installer.
  4.  
  5. Install the rocker arm/shaft assembly and tighten the bolts, in sequence, in 2-3 steps to 14-19 ft. lbs. (19-25 Nm). Make sure the rocker arm shaft spring does not get caught between the shaft and mounting boss during installation.
  6.  
  7. Install the seal plates and tighten the bolts to 69-95 inch lbs. (7.8-11.0 Nm).
  8.  
  9. Align and install the camshaft sprocket. Tighten the bolt to 52-59 ft. lbs. (71-80 Nm).
  10.  
  11. If installing the driver's side camshaft, apply clean engine oil to a new O-ring and install on the distributor spacer. Install the spacer and tighten the nuts to 69-95 inch lbs. (7.8-11.0 Nm). Install the distributor.
  12.  
  13. Install the cylinder head.
  14.  
  15. Install the blind cover and PCV valve.
  16.  
  17. Connect the negative battery cable.
  18.  
  19. Fill and bleed the cooling system.
  20.  
  21. Run the engine and check for leaks and proper operation. Check the idle speed and ignition timing.
  22.  

INSPECTION



Camshaft Lobe Lift

See Figure 8



Click image to see an enlarged view

Fig. Fig. 8: Checking camshaft lobe lift

2.3L, 2.5L, 2.6L AND 3.0L (MPV) ENGINES

Check the lift of each lobe in consecutive order and make a note of the readings. Camshaft assembly specifications are sometimes modified by Mazda after production. Refer to a local reputable machine shop as necessary.

  1. Remove the valve cover.
  2.  
  3. Measure the distance between the major (A-A) and minor (B-B) diameters of each cam lobe with a Vernier caliper and record the readings. The difference in the readings on each cam diameter is the lobe lift.
  4.  
  5. If the readings do not meet specifications, replace the camshaft and all rocker arms/cam followers.
  6.  
  7. Install the valve cover.
  8.  

3.0L (B SERIES PICK-UP) AND 4.0L ENGINES

Check the lift of each lobe in consecutive order and make a note of the reading. Camshaft assembly specifications are sometimes modify by MAZDA after production. Refer to a local reputable machine shop as necessary.

  1. Remove the fresh air inlet tube and the air cleaner. Remove the heater hose and crankcase ventilation hoses. Remove valve rocker arm cover(s).
  2.  
  3. Remove the rocker arm stud nut or fulcrum bolts, fulcrum seat and rocker arm.
  4.  
  5. Make sure the push rod is in the valve tappet socket. Install a dial indicator D78P-4201-B (or equivalent) so that the actuating point of the indicator is in the push rod socket (or the indicator ball socket adapter Tool 6565-AB is on the end of the push rod) and in the same plane as the push rod movement.
  6.  
  7. Disconnect the I terminal and the S terminal at the starter relay. Install an auxiliary starter switch between the battery and S terminals of the starter relay. Crank the engine with the ignition switch off. Turn the crankshaft over until the tappet is on the base circle of the camshaft lobe. At this position, the push rod will be in its lowest position.
  8.  
  9. Zero the dial indicator. Continue to rotate the crankshaft slowly until the push rod is in the fully raised position.
  10.  
  11. Compare the total lift recorded on the dial indicator with the specification. To check the accuracy of the original indicator reading, continue to rotate the crankshaft until the indicator reads zero. If the lift on any lobe is below specified wear limits, the camshaft and the valve tappet operating on the worn lobe(s) must be replaced.
  12.  
  13. Remove the dial indicator and auxiliary starter switch.
  14.  
  15. Install the rocker arm, fulcrum seat and stud nut or fulcrum bolts.
  16.  
  17. Install the valve rocker arm covers and the air cleaner.
  18.  

Camshaft End Play

See Figure 9



Click image to see an enlarged view

Fig. Fig. 9: Checking camshaft end play with the cylinder head removed from the engine

2.3L/2.5L ENGINES

See Figure 10



Click image to see an enlarged view

Fig. Fig. 10: Camshaft thrust plate installation on 2.3L/2.5L engines

Remove the camshaft drive belt cover. Push the camshaft toward the rear of the engine. Install a dial indicator so that the indicator point is on the camshaft sprocket attaching screw or gear hub. Zero the dial indicator. Position a prybar between the camshaft sprocket or gear and the cylinder head. Pull the camshaft forward and release it. Compare the dial indicator reading with specifications. If the end play is excessive, replace the thrust plate at the rear of the cylinder head. Remove the dial indicator and install the camshaft drive belt cover. The camshaft end-play specification is 0.001-0.007 inch and the service limit is 0.003 inch. Camshaft specifications are sometimes modified by Mazda after production.

2.6L AND 3.0L (MPV) ENGINES

On engines with an aluminum or nylon camshaft sprocket, prying against the sprocket, with the valve train load on the camshaft, can break or damage the sprocket. Therefore, the rocker arm adjusting nuts must be backed off, or the rocker arm and shaft assembly must be loosened sufficiently to free the camshaft.

  1. Push the camshaft toward the rear of the engine. Install a dial indicator so that the indicator point is on the camshaft sprocket attaching screw.
  2.  
  3. Zero the dial indicator. Position a prybar between the camshaft gear and the block. Pull the camshaft forward and release it. Compare the dial indicator reading with the specifications.
  4.  
  5. If the end play is excessive, check the spacer for correct installation before it is removed. If the spacer is correctly installed, replace the thrust plate.
  6.  
  7. Remove the dial indicator.
  8.  

3.0L (B SERIES PICK-UP) AND 4.0L ENGINES
  1. Push the camshaft toward the rear of the engine. Install a dial indicator (Tool D78P-4201-C or equivalent so that the indicator point is on the camshaft sprocket attaching screw.
  2.  
  3. Zero the dial indicator. Position a prybar between the camshaft gear and the block. Pull the camshaft forward and release it. Compare the dial indicator reading with the specification. The camshaft end-play specification is 0.0008-0.004 inch and the service limit is 0.009 inch (0.007 inch on 3.0L engine). Camshaft specifications are sometimes modified by Mazda after production.
  4.  
  5. If the end play is excessive, check the spacer for correct installation before it is removed. If the spacer is correctly installed, replace the thrust plate.
  6.  

The spacer ring and thrust plate are available in two thicknesses to permit adjusting the end play.

  1. Remove the dial indicator.
  2.  

 
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