Mazda Trucks 1972-1986 Repair Guide

Camshaft and Bearings

Print

REMOVAL & INSTALLATION 1,586cc, 1,796cc and 1,970cc Engines



See Figures 1, 2 and 3

Click image to see an enlarged view

Fig. Fig. 1: Exploded view of the 1,586cc, 1,796cc and 1,970cc engine cylinder head components



Click image to see an enlarged view

Fig. Fig. 2: Using a dial indicator to check the camshaft for straightness



Click image to see an enlarged view

Fig. Fig. 3: Measuring points to determine camshaft lobe wear

Perform this operation on a cold engine only.

  1. Scribe alignment marks on the hood hinges and remove the hood.
  2.  
  3. Remove the water pump.
  4.  
  5. Disconnect the coil wire and vacuum line from the distributor.
  6.  
  7. Rotate the crankshaft to place the No. 1 cylinder on TDC of the compression stroke. This can be determined by removing the spark plug and feeling compression with your thumb. When compression is felt, rotate the crankshaft until the pointer aligns with the TDC mark on the pulley.
  8.  
  9. Remove the plug wires and distributor cap. Remove the distributor.
  10.  
  11. Remove the valve cover.
  12.  
  13. Release the tension on the timing chain.
  14.  
  15. Remove the cylinder head bolts. Only do this on a cold engine.
  16.  
  17. Remove the rocker arm assembly.
  18.  
  19. Remove the nut, washer and distributor gear from the camshaft.
  20.  
  21. Remove the nut and washer holding the camshaft gear.
  22.  
  23. Remove the camshaft. Do not remove the camshaft gear from the timing chain. Be sure that the hear teeth and chain relationship is not disturbed. Wire the chain and cam gear to a place so that they will not fall into the front cover.
  24.  

To install:
  1. Clean all the gasket surfaces.
  2.  
  3. Clean the cylinder head bolt holes.
  4.  
  5. Install the camshaft on the head and install the camshaft gear.
  6.  
  7. Check the valve timing.
  8.  
  9. Install the rocker arm assembly.
  10.  
  11. Install and torque the head bolts.
  12.  
  13. Install the cam gear washer and nut.
  14.  
  15. Install the distributor gear, washer and nut.
  16.  
  17. Adjust the timing chain tension.
  18.  
  19. Check the camshaft end-play. It should be 0.025-0.180mm (0.00098-0.00708 in.). If it exceeds 0.20mm (0.00787 in.), replace the thrust plate with a new one.
  20.  
  21. Install the distributor, distributor cap and plug wires.
  22.  
  23. Connect the vacuum line and coil wire.
  24.  
  25. Adjust the valve clearance cold. Install the valve cover and fill the cooling system.
  26.  
  27. Run the engine and check for leaks. When normal operating temperature is reached, adjust the hot valve clearance.
  28.  
  29. Adjust the carburetor and ignition.
  30.  
  31. Install the air cleaner and hood.
  32.  

1,998cc Engine See Figures 4 and 5



Click image to see an enlarged view

Fig. Fig. 4: Installing the 1,998cc engine camshaft with the locating dowel/pin in the 12 o'clock position



Click image to see an enlarged view

Fig. Fig. 5: Sealant application areas on the 1,998cc cylinder head

  1. Disconnect the battery ground.
  2.  
  3. Drain the cooling system.
  4.  


CAUTION
When draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Remove the distributor.
  2.  
  3. Remove the fan shroud and fan.
  4.  
  5. Remove the alternator.
  6.  
  7. Disconnect the air injection pipes.
  8.  
  9. Remove the fan pulley, hub and bracket.
  10.  
  11. If so equipped, remove the air conditioning compressor drive belt.
  12.  
  13. If so equipped, remove the power steering pump drive belt.
  14.  
  15. Remove the crankshaft pulley and baffle plate.
  16.  
  17. Remove the upper, then the lower, belt covers.
  18.  
  19. Turn the crankshaft so that the A mark on the camshaft pulley is at the top, aligned with the notch in the front housing.
  20.  
  21. Loosen the tensioner lockbolt and remove the tensioner spring.
  22.  
  23. Mark the forward rotation of the belt with paint to avoid confusion upon installation. Remove the belt.
  24.  
  25. Insert a bar through the hole in the camshaft sprocket to hold it in position and remove the sprocket bolt.
  26.  
  27. Disconnect the accelerator cable, if necessary.
  28.  
  29. If equipped, disconnect the air bypass valve cable.
  30.  
  31. Disconnect the spark plug wires. Remove the wires from the spark plug wire clips on the rocker covers and position them out of the way.
  32.  
  33. Remove the rocker cover and discard the gasket.
  34.  
  35. Remove the rocker arm shaft attaching bolts evenly in the order shown, and remove the rocker arm shafts.
  36.  
  37. Remove the camshaft rear seal cap.
  38.  
  39. Lift out the camshaft.
  40.  
  41. Inspect the camshaft for wear, heat scoring or obvious damage. Replace it if necessary. Check the lobes and journals for wear according to the specifications in the Camshaft Specification Chart.
  42.  

To install:
  1. Coat the camshaft with clean engine oil and install it in position, making sure that the lug on the nose of the shaft is at the 12 o'clock position.
  2.  
  3. Apply a thin coat of sealant to the areas shown, and install the rocker shaft assembly. Torque the bolts evenly, and in the order shown, to 15-20 ft. lbs. Install the camshaft sprocket. Torque the camshaft sprocket bolt to 40-45 ft. lbs.
  4.  
  5. Replace the belt if it has been contaminated by oil or grease, or shows any sign of damage, wear, cracks or peeling.
  6.  
  7. To ease installation of the belt, remove all the spark plugs.
  8.  
  9. Make sure that the timing mark on the camshaft is aligned as described above, and that the timing mark (notch) on the crankshaft sprocket is aligned with the triangular shaped mark on the front housing.
  10.  
  11. Install the tensioner and spring, positioning the tensioner all the way to the intake manifold side and temporarily secure it there with the lockbolt.
  12.  
  13. Install the belt onto the sprockets from YOUR right side. If you are reusing the original belt, make sure you follow the directional mark previously made.
  14.  
  15. Loosen the lockbolt so that the tensioner applies tension to the belt.
  16.  
  17. Turn the crankshaft two full revolutions in the direction of normal rotation. This will apply equal tension to all points of the belt.
  18.  
  19. Make sure that the timing marks are still aligned. If not, repeat the belt installation procedure.
  20.  
  21. Tighten the tensioner lockbolt to 30-35 ft. lbs.
  22.  
  23. Measure the timing belt tension by pressing on the belt at the midpoint of the longest straight run. Belt deflection should be 11-13mm (0.433-0.510 in.). If not, repeat the belt adjustment procedure, above.
  24.  
  25. Check the valve adjustment and reset, if necessary.
  26.  
  27. Clean the mating surfaces of the cylinder head and rocker cover.
  28.  
  29. Install the rocker cover with a new gasket.
  30.  
  31. Torque the bolts to 24-36 inch lbs.
  32.  
  33. Install the spark plug wire on the plugs. Place the wires in the clips on the rocker cover. Connect the choke and air by-pass valve cable.
  34.  
  35. Install the lower, then the upper, belt covers. Torque the belt cover bolts to 80 in. lbs.
  36.  
  37. Install the power steering pump drive belt.
  38.  
  39. Install the air conditioning compressor drive belt.
  40.  
  41. Install the fan pulley, hub and bracket. Torque the fan bracket bolts to 40 ft. lbs.
  42.  
  43. Connect the air injection pipes.
  44.  
  45. Install the alternator.
  46.  
  47. Install the fan shroud and fan.
  48.  
  49. Install the distributor.
  50.  
  51. Fill the cooling system.
  52.  
  53. Connect the battery ground.
  54.  

When installing the drive belts on the various accessories, check the belt deflection as follows:



Alternator
 

New: 7-8mm (0.276-0.315 in.) Used: 8-9mm (0.315-0.354 in.)



Power steering pump
 

New: 9-11mm (0.354-0.433 in.) Used: 11-13mm (0.433-0.510 in.)



Air conditioning compressor
 

New: 10-12mm (0.394-0.472 in.) Used: 12-14mm (0.472-0.552 in.) 2,209cc Diesel Engine

  1. Scribe the locations of the hood hinges and remove the hood.
  2.  
  3. Remove the engine splash shield.
  4.  
  5. Drain the coolant.
  6.  


CAUTION
When draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Drain the engine oil.
  2.  


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 you 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. Disconnect the battery cables and remove the battery.
  2.  
  3. Remove the air cleaner and the oil dipstick.
  4.  
  5. Remove the radiator shroud and the engine fan. Place the fan in an upright position to avoid fluid loss from the fan clutch.
  6.  
  7. Disconnect and tag all wires, hoses, cables, pipes and linkage from the engine.
  8.  
  9. Remove the clutch release cylinder.
  10.  
  11. Remove the oil cooler.
  12.  
  13. Remove the radiator.
  14.  
  15. Disconnect the exhaust pipe at the manifold and remove the exhaust manifold.
  16.  
  17. Dismount the air conditioning compressor and position it out of the way. Don't disconnect any refrigerant lines.
  18.  
  19. Dismount the power steering pump and position it out of the way without disconnecting any hoses.
  20.  
  21. Raise and support the truck on jackstands.
  22.  
  23. Attach a lifting sling and shop crane to the engine lifting eyes and take up the weight of the engine.
  24.  
  25. Support the transmission with a floor jack and remove the transmission-to-engine bolts.
  26.  
  27. Remove the engine support plates and mounting nuts, push the engine forward to clear the transmission and lift it out of the truck.
  28.  
  29. Remove the rocker arm cover, rocker arm assemblies and pushrods, making sure you keep the pushrods in order of their removal. Remove the lifters, marking them also, for installation.
  30.  
  31. Remove the timing gear case cover.
  32.  
  33. Remove the camshaft gear.
  34.  
  35. Remove the oil pan and oil pump.
  36.  
  37. Remove the camshaft thrust plate.
  38.  
  39. Carefully slide the camshaft from the block.
  40.  
  41. Inspect the camshaft for wear, damage or heat scoring. Check the dimensions of the shaft according to the specifications given in the Camshaft Specifications Chart.
  42.  

To install:
  1. Coat the camshaft journal and bearings with clean engine oil, and the lobes with polyethylene grease, prior to installation.
  2.  
  3. Carefully slide the camshaft into the block.
  4.  
  5. Install the camshaft thrust plate and new gasket. Torque the thrust plate bolts to 95 inch lbs.
  6.  
  7. Install the oil pump.
  8.  
  9. Install the oil pan.
  10.  
  11. Install the camshaft gear.
  12.  
  13. Install the timing gear case cover and new gasket.
  14.  
  15. Install the lifters.
  16.  
  17. Install the pushrods.
  18.  
  19. Install the rocker assemblies.
  20.  
  21. Install the rocker arm cover.
  22.  
  23. Lower the engine into the truck and push it rearward to engage the transmission.
  24.  
  25. Install the support plates and mounting nuts. Torque the fasteners to 35 ft. lbs.
  26.  
  27. Install the transmission-to-engine bolts. Torque them to 35 ft. lbs.
  28.  
  29. Remove the shop crane.
  30.  
  31. Install the power steering pump.
  32.  
  33. Install the air conditioning compressor.
  34.  
  35. Install the exhaust manifold.
  36.  
  37. Connect the exhaust pipe at the manifold.
  38.  
  39. Install the radiator.
  40.  
  41. Install the oil cooler.
  42.  
  43. Install the clutch release cylinder.
  44.  
  45. Connect all wires, hoses, cables, pipes and linkage at the engine.
  46.  
  47. Install the engine fan.
  48.  
  49. Install the radiator shroud.
  50.  
  51. Install the air cleaner.
  52.  
  53. Install the oil dipstick.
  54.  
  55. Install the battery.
  56.  
  57. Connect the battery cables.
  58.  
  59. Fill the engine with the proper amount of oil.
  60.  
  61. Fill the cooling system.
  62.  
  63. Install the engine splash shield.
  64.  
  65. Install the hood.
  66.  

INSPECTION Camshaft Lobe Lift



Check the lift of each lobe in consecutive order and make a note of the reading.

  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 pushrod is in the valve tappet socket. Install a dial indicator so that the actuating point of the indicator is in the pushrod socket (or the indicator ball socket adaptor is on the end of the pushrod) and in the same plane as the pushrod movement.
  6.  
  7. Install an auxiliary starter switch. 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 pushrod will be in its lowest position.
  8.  
  9. Zero the dial indicator. Continue to rotate the crankshaft slowly until the pushrod is in the fully raised position.
  10.  
  11. Compare the total lift recorded on the dial indicator with the specification shown on the Camshaft Specification chart.
  12.  

To check the accuracy of the original indicator reading, continue to rotate the crankshaft until the indicator reads zero. If the left on any lobe is below specified wear limits listed, the camshaft and the valve tappet operating on the worn lobe(s) must be replaced.

  1. Install the dial indicator and auxiliary starter switch.
  2.  
  3. Install the rocker arm, fulcrum seat and stud nut or fulcrum bolts. Check the valve clearance. Adjust if required (refer to procedure in this section).
  4.  
  5. Install the valve rocker arm cover(s) and the air cleaner.
  6.  

Camshaft End-Play

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. After checking the camshaft end-play, check the valve clearance. Adjust if required (refer to procedure in this section).

  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.  

 
label.common.footer.alt.autozoneLogo