Mazda 323/626/929/GLC/MX-6/RX-7 1978-1989

Cylinder Head

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REMOVAL & INSTALLATION



Gasoline Engines
GLC AND 1979-82 626

See Figures 1, 2, 3 and 4

Be sure that the cylinder head is cold before removal, as this will help prevent warpage.

  1. Disconnect the negative battery cable.
  2.  
  3. Rotate the crankshaft so that the No. 1 cylinder is at TDC.
  4.  
  5. Drain the cooling system.
  6.  
  7. Remove the air cleaner assembly.
  8.  
  9. On rear wheel drive models, remove the water pump.
  10.  
  11. Remove the distributor, as described earlier in this section.
  12.  
  13. Disconnect the front catalytic converter from the exhaust manifold, then unfasten and remove the exhaust manifold from the cylinder head.
  14.  
  15. Disconnect all applicable electrical wires and leads.
  16.  
  17. If necessary, remove the alternator drive belt, alternator and adjusting strap.
  18.  
  19. Remove the thermostat housing and thermostat.
  20.  



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Fig. Fig. 1: Removing the tensioner-GLC front wheel drive models



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Fig. Fig. 2: Cylinder head bolt loosening sequence for GLC and 1979-82 626 (1981-85 GLC shown)



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Fig. Fig. 3: Wire the camshaft sprocket and timing chain together to maintain their proper relationship



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Fig. Fig. 4: Cylinder head bolt tightening sequence for GLC and 1979-82 626 (1981-85 GLC shown)

  1. Disconnect the accelerator linkage.
  2.  
  3. Remove the intake manifold and carburetor assembly.
  4.  
  5. Remove the rocker arm cover and gasket, along with the semi-circular oil seal(s). Clean the mating surface of the rocker arm cover.
  6.  
  7. On front wheel drive GLC models, remove the tensioner (chain adjuster) from the timing chain cover.
  8.  
  9. Remove the locknut, washer and, on the 626 and GLC wagon only, the distributor drive gear and spacer from the camshaft.
  10.  
  11. If so equipped, remove the cylinder head-to-cylinder block bolt.
  12.  

Although 1.3L and 1.4L engines have their camshaft sprocket at the opposite end, they utilize the same loosening sequence (in reference to the front of the vehicle).

  1. Loosen the cylinder head bolts in several stages of the illustrated sequence. (In order to avoid cylinder head distortion, only loosen the bolts a few turns at a time.)
  2.  

The cylinder head bolts also retain the rocker arm assembly and camshaft.

  1. Remove the rocker arm assembly.
  2.  
  3. Separate the camshaft sprocket and chain from the camshaft. Be sure to support the timing chain so the tensioner will not come apart. On the front wheel drive GLC, even though the tensioner has been removed, you still must support the camshaft sprocket so the timing relationship between the chain links and upper/lower sprockets will not be lost.
  4.  

Do not remove the camshaft sprocket from the chain. Maintain the relationship between the timing chain and sprocket by temporarily wiring them together.

  1. Remove the camshaft.
  2.  
  3. Lift off the cylinder head and remove the gasket. Thoroughly clean off all old gasket material from the mating surfaces and inspect the components for wear or damage, as described later in this section. Repair or replace parts, as necessary.
  4.  

To install:
  1. Install a new head gasket on the engine block with all oil passages, water passages, and bolt holes matching up.
  2.  
  3. Place the cylinder head into position, aligning the dowels.
  4.  
  5. Coat all the camshaft bearing surfaces with clean engine oil before installing the camshaft. (These include the cylinder head and cap or bearing insert inner surfaces, as well as the camshaft journal surfaces).
  6.  
  7. Slide the sprocket (with the timing chain still attached) onto the camshaft. Install the camshaft and rocker arm assembly.
  8.  

The rocker arm assembly must be properly positioned before tightening the cylinder head bolts.

  1. Slide the rocker arm assembly to one side until the adjusting studs are offset 0.04 in. (1mm) from the centers of the valve stems. (This is necessary for proper valve rotation.) Then, torque the bolts using several stages of the indicated sequence.
  2.  

Although 1.3L and 1.4L engines have their camshaft sprocket at the opposite end, they utilize the same tightening sequence (in reference to the front of the vehicle).

  1. Check the valve clearance using a feeler gauge and adjust, if necessary, as described in Engine Electrical .
  2.  
  3. If applicable, install the cylinder head-to-cylinder block bolt.
  4.  
  5. On the 626 and GLC wagon, align the key groove with the pin, then install the spacer and distributor drive gear on the camshaft.
  6.  
  7. Install the washer and sprocket locknut on the camshaft. Tighten the locknut to 51-58 ft. lbs. (70-80 Nm).
  8.  
  9. Check the camshaft end-play (clearance between the sprocket and thrust plate) with a feeler gauge. If the clearance exceeds 0.008 in. (0.20mm), replace the thrust plate.
  10.  
  11. On front wheel drive GLC models, reset the chain adjuster by pushing the sleeve completely into the body, then securing it with the built-in latch and pin. Install this device on the timing chain cover.
  12.  

After the adjuster is installed, the pin is automatically released by the timing chain when the engine is cranked.

  1. Apply RTV or rubber sealer to the semi-circular oil seal(s) and install on the cylinder head with the "OUT" mark facing away from the engine.
  2.  
  3. Position a new gasket on the cylinder head, then install the rocker arm cover. Tighten the retaining nuts to 1.1-1.4 ft. lbs. (1.5-1.9 Nm), or the bolts to 1.4-2.5 ft. lbs. (1.9-3.4 Nm).
  4.  
  5. Complete the installation of the remaining components in reverse of the removal procedure. Be sure to use new gaskets and O-rings, and to properly tension the drive belt, if necessary.
  6.  
  7. Refill the cooling system to the proper level and connect the negative battery cable. Start the engine and check for leaks.
  8.  

1983-85 626

See Figures 5, 6, 7, 8, 9, 10, 11 and 12

Be sure that the cylinder head is cold before removal, as this will help prevent warpage.

  1. Rotate the crankshaft so that the No. 1 cylinder is at TDC.
  2.  
  3. Drain the cooling system.
  4.  
  5. Remove the air cleaner assembly.
  6.  
  7. Remove the distributor, as described earlier in this section.
  8.  
  9. Remove the thermostat housing and thermostat.
  10.  



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Fig. Fig. 5: With the bolts removed, use a prytool to carefully separate the cylinder head from the engine block



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Fig. Fig. 6: Lift the cylinder head from the engine block



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Fig. Fig. 7: Remove the cylinder head gasket from the engine block



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Fig. Fig. 8: Cylinder head bolt tightening sequence-1983-87 626



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Fig. Fig. 9: Exploded view of the cylinder head and upper engine components-1983-85 626



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Fig. Fig. 10: Cylinder head bolt loosening sequence-1983-87 626



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Fig. Fig. 11: Torque the cylinder head bolts in several stages, beginning with the front center bolt



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Fig. Fig. 12: Apply sealant to the shaded areas (indicated by the arrows) before installing the rocker arm cover-1983-87 626

  1. Remove the fuel pump.
  2.  
  3. Disconnect the accelerator cable.
  4.  
  5. Remove the intake manifold and carburetor assembly.
  6.  
  7. On vehicles equipped with air conditioning, remove the alternator and alternator strap.
  8.  
  9. On vehicles equipped with air conditioning, remove the A/C compressor and alternator bracket installation bolts.
  10.  
  11. Disconnect the engine ground wire.
  12.  
  13. Remove the upper timing belt cover.
  14.  
  15. Remove the timing belt, as described later in this section.
  16.  
  17. Disconnect the secondary air pipes.
  18.  
  19. Unfasten the oxygen sensor connector.
  20.  
  21. Remove the exhaust manifold insulator assembly.
  22.  
  23. Remove the three nuts and gasket which retain the front catalytic converter to the exhaust manifold.
  24.  
  25. Remove the cylinder head's rear housing and gasket.
  26.  
  27. Remove the rocker arm cover and gasket.
  28.  
  29. Remove the cylinder head bolts and washers in the appropriate sequence, as illustrated.
  30.  

In order to avoid cylinder head distortion, loosen and remove the cylinder head bolts only a few turns at a time.

  1. Remove the cylinder head and exhaust manifold as an assembly. If necessary, first unfasten and remove the exhaust manifold from the cylinder head.
  2.  

Exhaust manifold removal is normally unnecessary in order to remove the cylinder head.

  1. Remove the cylinder head gasket. Thoroughly clean off all old gasket material from the mating surfaces and inspect the components for wear or damage, as described later in this section. Repair or replace parts, as necessary.
  2.  

To install:
  1. If applicable, re-attach the exhaust manifold to the cylinder head, using a new gasket. (If preferred, this step may be performed after the cylinder head is installed.)
  2.  
  3. Install a new head gasket on the engine block with all oil passages, water passages, and bolt holes matching up.
  4.  
  5. Place the cylinder head into position, then insert the cylinder head washers and bolts. Torque the bolts to 59-65 ft. lbs. (82-88 Nm) in several stages, following the proper sequence.
  6.  
  7. Position a new gasket on the rocker arm cover. Apply a coating of sealant to the portions of the rocker shaft assembly which are shaded in the illustration, then position the gasket and cover on the cylinder head. Insert the retaining bolts with their seal washers and tighten to 2.2-2.9 ft. lbs. (3-4 Nm).
  8.  
  9. Complete the installation of the remaining components in reverse of the removal procedure. Be sure to use new gaskets and O-rings, and to properly tension the drive belt(s). For information on timing belt installation and adjustment, refer to the procedure later in this section.
  10.  
  11. Refill the cooling system to the proper level. Start the engine and check for leaks.
  12.  

1986-87 626

See Figures 8, 10, 12 and 13

  1. Disconnect all applicable electrical wires and leads.
  2.  
  3. Disconnect the drive belt(s), then remove the alternator.
  4.  
  5. Remove the cylinder head's rear housing and gasket.
  6.  

Be sure that the cylinder head is cold before removal, as this will help prevent warpage.

  1. Disconnect the negative battery cable.
  2.  
  3. Drain the cooling system.
  4.  
  5. Disconnect the accelerator cable.
  6.  
  7. On turbocharged models, disconnect the secondary air pipe from the exhaust manifold.
  8.  
  9. Remove the distributor.
  10.  
  11. Remove the rear housing and gasket.
  12.  



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Fig. Fig. 13: Exploded view of the cylinder head and upper engine components-1986-87 626 turbo

  1. Disconnect the intake air hose.
  2.  
  3. On turbo models, disconnect the secondary air pipes from the front catalytic converter. Then, disconnect the oil pipe from the turbocharger.
  4.  
  5. Remove the exhaust manifold insulator. On turbo models, also remove the two smaller insulators near the front catalytic converter.
  6.  
  7. On turbo models, remove the bracket connecting the turbocharger to the front catalytic converter. Disconnect the front catalytic converter and the oil return hose from the turbocharger. Then, disconnect the water inlet and outlet hoses, and the EGR pipe.
  8.  
  9. On non-tubo models, disconnect the exhaust pipe from the manifold.
  10.  
  11. Remove the exhaust manifold (or manifold/turbocharger assembly) and gasket.
  12.  
  13. Remove the intake manifold assembly and gasket.
  14.  
  15. Remove the upper timing belt cover.
  16.  
  17. Remove the timing belt, as described later in this section.
  18.  
  19. Remove the rocker arm cover.
  20.  
  21. In order to avoid cylinder head distortion, loosen and remove the cylinder head bolts only a few turns at a time. The bolts should be removed in the appropriate sequence, as illustrated.
  22.  
  23. Lift off the cylinder head and remove the gasket. Thoroughly clean off all old gasket material from the mating surfaces and inspect the components for wear or damage, as described later in this section. Repair or replace parts, as necessary.
  24.  

To install:
  1. Install a new head gasket on the engine block with all oil passages, water passages, and bolt holes matching up.
  2.  
  3. Place the cylinder head into position, then insert the cylinder head washers and bolts. Torque the bolts to 59-65 ft. lbs. (82-88 Nm) in several stages, following the proper sequence.
  4.  
  5. Position a new gasket on the rocker arm cover. Apply a coating of sealant to the portions of the rocker shaft assembly which are shaded in the illustration, then position the gasket and cover on the cylinder head. Insert the retaining bolts with their seal washers and tighten to 2.2-2.9 ft. lbs. (3-4 Nm).
  6.  
  7. Complete the installation of the remaining components in reverse of the removal procedure. Be sure to use new gaskets and O-rings, and to properly tension the drive belt(s). For information on timing belt installation and adjustment, refer to the procedure later in this section.
  8.  
  9. Refill the cooling system to the proper level. Start the engine and check for leaks.
  10.  

1986-89 323 NON-TURBO

See Figures 14, 15, 16 and 17

  1. Disconnect the negative battery cable and drain the cooling system.
  2.  
  3. Remove or disconnect the following parts:

    Air cleaner
     
    Oil dipstick
     
    Accelerator cable and (if so equipped) cruise control cable
     
    Fuel hoses (drain fuel into a suitable container, then plug them)
     
    Fuel pump (carbureted engines only)
     
    Heater hoses
     
    Power brake vacuum hose
     
    Emissions canister hoses
     
    Engine electrical harness connectors
     
    High tension wires (label them first)
     
    Distributor
     
    Spark plugs
     
    Secondary air pipe assembly (carbureted engines only)
     
    Front engine hanger and the nearby ground wire
     
    Upper radiator hose (at the thermostat housing)
     
    Water bypass hose and bracket
     
    Intake and exhaust manifolds
     
    Engine side cover
     
    Alternator and drive belt(s)
     
    Water pump pulley
     
    Crankshaft pulley and baffle plate
     

  4.  
  5. Remove the timing belt covers, as described later in this section. Rotate the crankshaft until the matchmarks on the camshaft and timing belt pulleys are aligned with the corresponding marks on the cylinder block. Then, remove the timing belt, also as described later in this section.
  6.  



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Fig. Fig. 14: Cylinder head bolt loosening sequence-1986-87 323 non-turbo



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Fig. Fig. 15: Cylinder head bolt loosening sequence-1988-89 323 non-turbo



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Fig. Fig. 16: Cylinder head bolt torque sequence-1986-87 323 non-turbo



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Fig. Fig. 17: Cylinder head bolt torque sequence-1988-89 323 non-turbo

  1. If you will be removing the camshaft or performing other major work on the cylinder head itself, remove the camshaft pulley. To remove the pulley, insert a small prytool in one of the slots on the face of the pulley to hold it in place while loosening the bolt with a wrench. After removing the bolt, withdraw the pulley from the camshaft.
  2.  
  3. If you will be removing the camshaft or performing other major work on the cylinder head itself, also remove the rocker assembly, as described earlier in this section.
  4.  
  5. Remove the rear engine hanger from the cylinder head.
  6.  
  7. Loosen the cylinder head cover retaining bolts and remove the cover.
  8.  
  9. Loosen the cylinder head bolts using several stages of the the sequence shown. Remove the head bolts, then lift off the cylinder head and head gasket. If necessary, remove the thermostat cover and thermostat.
  10.  
  11. Thoroughly clean both mating surfaces and inspect the components for warping or other damage, as described later in this section. Repair or replace parts, as necessary.
  12.  

To install:
  1. If removed, install the thermostat with the jiggle pin facing upward and the printed side of the new gasket facing the thermostat. Torque the cover bolts to 14-19 ft. lbs. (19-26 Nm).
  2.  
  3. Install a new head gasket on the engine block with all oil passages, water passages, and bolt holes matching up.
  4.  
  5. Place the cylinder head into position and install the head bolts finger-tight. Then, torque the cylinder head bolts to 63-67 ft. lbs. (85-91 Nm) in three stages, using the appropriate sequence.
  6.  

Step 11 of the torque sequence only applies to 1988 engines.

  1. Install the camshaft pulley onto the end of the camshaft with the dowel pin and keyway in proper positions and the matchmark straight up. Install the retaining bolt and torque it to 36-45 ft. lbs. (49-61 Nm).
  2.  
  3. Perform the remaining installation steps in reverse of the removal procedure. Note the following points:
    1. Replace all gaskets which were removed with new ones.
    2.  
    3. Install and adjust the timing belt, as described later in this section.
    4.  
    5. If applicable, install the rocker assembly following the torque sequence and specifications outlined earlier in this section.
    6.  
    7. Torque the intake and exhaust manifold bolts/nuts to specification.
    8.  
    9. When installing the distributor, be sure that the distributor rotor is pointing in the direction of the No. 1 cylinder wire connection at the cap. The distributor's drive blade should then be aligned with the oil hole on the base of the distributor prior to engaging the distributor drive gear with the corresponding gear on the camshaft.
    10.  
    11. Adjust the valves as described in Engine Electrical .
    12.  
    13. Apply a coating of sealer along the groove in the cylinder head cover before installing the gasket, and torque the bolts to 43-78 inch lbs. (5-9 Nm).
    14.  
    15. Refill the cooling system and connect the negative battery cable.
    16.  
    17. Start the engine and check for leaks.
    18.  

  4.  

1988-89 323 TURBO

See Figures 18 and 19

  1. Properly relieve the fuel system pressure. Disconnect the negative battery cable. Drain the cooling system.
  2.  
  3. Remove the air cleaner assembly.
  4.  
  5. Remove the distributor, distributor wires and spark plugs.
  6.  
  7. Remove the air intake pipe, air pipe, air bypass valve and hoses.
  8.  
  9. Remove the radiator.
  10.  
  11. Remove the engine side cover and the engine under cover.
  12.  
  13. Disconnect the exhaust pipe at the exhaust manifold. Remove the turbocharger mounting bracket, along with the the exhaust manifold and turbocharger insulators. Unfasten the exhaust manifold retaining bolts, then remove the exhaust manifold and turbocharger assembly from the engine.
  14.  
  15. Remove the radiator hose and coolant bypass pipe. Disconnect the accelerator cable.
  16.  



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Fig. Fig. 18: Cylinder head bolt loosening sequence-323 turbo



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Fig. Fig. 19: Cylinder head bolt torque sequence-323 turbo

  1. Disconnect all required electrical connections, vacuum hoses and fuel line couplings.
  2.  
  3. Remove the surge tank and bracket.
  4.  
  5. Loosen the cylinder head cover retaining bolts and remove the cover.
  6.  
  7. Remove the timing cover assembly retaining bolts. Remove the timing cover assembly.
  8.  
  9. Remove the timing belt, as described later in this section.
  10.  
  11. Loosen the cylinder head bolts gradually in the appropriate sequence. Remove the cylinder head and intake manifold assembly from the engine.
  12.  
  13. Remove the attaching bolts and separate the intake manifold from the cylinder head. If necessary, remove the thermostat cover and thermostat. Remove any old gasket material and clean all gasket mounting surfaces.
  14.  
  15. Thoroughly clean the cylinder head and engine block mating surfaces, then inspect the components for warping or other damage, as described later in this section. Repair or replace parts, as necessary.
  16.  

To install:
  1. If removed, install the thermostat with the jiggle pin facing upward and the printed side of the new gasket facing the thermostat. Torque the cover bolts to 14-19 ft. lbs. (19-26 Nm).
  2.  
  3. Install the intake manifold with a new gasket. Torque the intake manifold bolts to 14-19 ft. lbs. (19-26 Nm).
  4.  
  5. Place a new head gasket onto the engine block and position the cylinder head. Install the bolts and torque them to 56-60 ft. lbs. (76-81 Nm) in several stages, following the proper sequence.
  6.  

Step 11 of the torque sequence only applies to 1988 engines.

  1. Apply sealant to the cylinder head cover and install a new gasket. Torque the cover bolts to 26-35 inch lbs. (3-4 Nm).
  2.  
  3. Complete the installation of the remaining components in reverse of the removal procedure.
  4.  
  5. Refill the cooling system to the proper level and connect the negative battery cable.
  6.  
  7. Start the engine and check for leaks. Perform any necessary tune-up adjustments.
  8.  

1988-89 626/MX-6

See Figures 20, 21 and 22

  1. Disconnect the negative battery cable and drain the cooling system.
  2.  
  3. Disconnect the spark plug wires and remove the spark plugs.
  4.  
  5. Disconnect the accelerator cable. If equipped with an automatic transaxle, disconnect the throttle cable and route it off to the side.
  6.  
  7. Remove the air intake pipe.
  8.  
  9. Remove the air intake pipe and fuel hose. Cover the fuel hose to prevent leakage.
  10.  
  11. Remove the upper radiator hose, water bypass hose, heater hose, oil cooler hose (turbo only) and brake vacuum hose.
  12.  
  13. Remove the 3-way and EGR solenoid valve assemblies.
  14.  



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Fig. Fig. 20: Camshaft pulley and front housing alignment marks-1988-89 626 and MX-6



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Fig. Fig. 21: Cylinder head bolt loosening sequence-1988-89 626 and MX-6



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Fig. Fig. 22: Cylinder head bolt torque sequence-1988-89 626 and MX-6

  1. Disconnect the engine harness connector and ground wire.
  2.  
  3. Remove the vacuum chamber and exhaust manifold insulator.
  4.  

  1. Remove the EGR pipe, turbo oil pipes (if so equipped) and exhaust pipe.
  2.  
  3. Remove the exhaust manifold and the turbocharger, if so equipped.
  4.  
  5. Remove the intake manifold bracket and the intake manifold.
  6.  
  7. Remove the distributor, as described earlier in this section.
  8.  
  9. Loosen the air conditioning compressor and bracket assembly; position and tie it off to the side and out of the way.
  10.  

Do not disconnect the refrigerant lines.

  1. Remove the upper timing belt cover and the timing belt tensioner spring.
  2.  
  3. To remove the timing belt, perform the following:
    1. Rotate the crankshaft so that the 1 on the camshaft pulley is aligned with the timing mark on the front housing (see illustration).
    2.  
    3. When the timing marks are aligned, loosen the timing belt tensioner lockbolt. Pull the tensioner as far out as it will go, then temporarily tighten the lockbolt to hold it there.
    4.  
    5. Lift the timing belt from the camshaft pulley and position it out of the way.
    6.  

  4.  
  5. Loosen the retaining bolts, then remove the cylinder head cover and gasket.
  6.  
  7. Loosen the cylinder head bolts in the proper sequence, then remove the cylinder head and head gasket.
  8.  
  9. Thoroughly clean the cylinder head and engine block mating surfaces, then inspect the components for warping or other damage as described later in this section. Repair or replace parts as necessary.
  10.  

To install:
  1. Position a new head gasket on the mating surface of the engine block.
  2.  

Turbocharged and non-turbocharged engines use different cylinder head gaskets. To ensure proper sealing and compression, make sure that the proper type gasket is being installed.

  1. Position the cylinder head on the gasket.
  2.  
  3. Coat the cylinder head bolt threads and seat faces with clean engine oil, then torque the bolts to 59-64 ft. lbs. (80-87 Nm) in three stages, following the proper sequence.
  4.  
  5. Apply a suitable sealant to the 4 corners where the rocker assembly end caps meet the cylinder head, then install the cylinder head cover with a new gasket. Torque the cover bolts to 52-69 inch lbs. (6-8 Nm).
  6.  
  7. Make sure that the camshaft pulley and front housing timing marks are still aligned, then install the timing belt, as described later in this section.
  8.  
  9. Complete the remainder of the installation procedures in reverse of their removal. Be sure to replace all gaskets which were removed with new ones.
  10.  
  11. Refill the cooling system to the proper level and connect the negative battery cable.
  12.  
  13. Start the engine and check for leaks. Check and adjust the ignition timing and idle speed, as described in Engine Electrical .
  14.  

929

See Figures 23, 24, 25, 26 and 27

The following procedure applies to removal of either side cylinder head.

  1. Properly relieve the fuel system pressure. Disconnect the negative battery cable.
  2.  
  3. Drain the coolant and remove the air cleaner assembly.
  4.  
  5. Rotate the crankshaft so that the No. 1 cylinder is at TDC. (All the pulley matchmarks should be aligned.)
  6.  
  7. Remove the timing cover assembly. Mark the timing belt's direction of rotation (if it will be re-used), then remove the belt.
  8.  
  9. Disconnect and plug the canister, brake vacuum and fuel hoses. If equipped with an automatic transmission, disconnect the automatic transmission vacuum hose.
  10.  
  11. Remove the 3-way solenoid valve assembly and disconnect all engine harness connectors and grounds.
  12.  
  13. If equipped with an automatic transmission, remove the dipstick. Disconnect the required vacuum hoses. Disconnect the accelerator linkage.
  14.  
  15. Remove the distributor, as described earlier in this section, and the EGR pipe.
  16.  

  1. Remove the six extension manifolds. Remove and discard the O-rings from the extension manifolds (new ones must be used). Remove the intake manifold by loosening the retaining bolts in the proper sequence.
  2.  
  3. Remove the cylinder head cover, gasket and seal washers.
  4.  
  5. Remove the insulator and center exhaust pipe pipe. Disconnect the exhaust manifold retaining bolts. Remove the exhaust manifold with insulator.
  6.  
  7. Remove the seal plate.
  8.  



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Fig. Fig. 23: Cylinder head bolt loosening sequence-929



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Fig. Fig. 24: Measure the length of each head bolt before installation, and replace any that do not meet specifications-929



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Fig. Fig. 25: Be sure to properly position the cylinder head gaskets with the marks facing up-929



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Fig. Fig. 26: Cylinder head bolt torque sequence-929



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Fig. Fig. 27: After tightening the head bolts to specification, paint a reference mark on each bolt head and use the angular torque method to achieve proper final torque-929

  1. Remove the cylinder head retaining bolts in the proper sequence, in 2 or 3 stages. Remove the cylinder head from the vehicle.
  2.  
  3. Thoroughly clean the cylinder head and engine block mating surfaces, then inspect the components for warping or other damage, as described later in this section. Repair or replace parts, as necessary.
  4.  

To install:
  1. After they have been cleaned, measure the length of each cylinder head bolt. Replace any out-of-specifications bolts as required.
  2.  

Length:


Intake-4.25-4.29 in. (108-109mm)
 
Exhaust-5.43-5.47 in. (138-139mm)
 

  1. Check the oil control plug projection at the cylinder block. The projection should be 0.0209-0.0224 in. (0.53-0.57mm). If correct, apply clean engine oil to a new O-ring and position it on the control plug.
  2.  
  3. Position the new correct side cylinder head gasket on the engine block.
  4.  

A left bank gasket should be positioned with theLmark facing up, and a right bank gasket should be positioned with theRmark facing up.

  1. Install the cylinder head onto the block. Tighten the head bolts in the following manner:
    1. Coat the threads and the seating faces of the head bolts with clean engine oil.
    2.  
    3. Torque the bolts in the proper sequence to 14 ft. lbs. (19 Nm).
    4.  
    5. Paint a mark on the head of each bolt.
    6.  
    7. Using this mark as a reference, tighten the bolts in the proper sequence an additional 90 degrees.
    8.  
    9. Repeat Step d.
    10.  

  2.  
  3. Complete the installation of the remaining components in reverse of their removal. Be sure to replace all gaskets which were removed with new ones. For timing belt installation and adjustment, refer to the procedure later in this section.
  4.  
  5. Refill the cooling system to the proper level and connect the negative battery cable.
  6.  
  7. Start the engine and check for leaks. Perform any required tune-up adjustments.
  8.  

Diesel Engines

See Figures 28, 29, 30 and 31

To perform this procedure, you will need two size M8 x 1.25 x 45mm bolts, a wheel puller for a selection of bolts with metric threads, and plastic caps (or another appropriate means to seal off fuel injection line openings).

  1. Disconnect the negative battery cable. Disconnect the air cleaner hose at the intake manifold.
  2.  
  3. Position a suitable pan, then drain the coolant by opening the radiator drain plug.
  4.  
  5. Disconnect the following hoses/electrical connectors at the cylinder head:

    Heater outlet hose at the oil cooler
     
    Upper radiator hose at both ends
     
    Fuel supply and return hoses at the injection pump (and plug or cap the hoses and pump openings, once disconnected)
     
    Temperature gauge sending unit electrical connector
     
    Glow plug electrical connector
     
    Engine ground strap
     

  6.  
  7. Disconnect the exhaust pipe at the exhaust manifold. Then, remove the right side splash shield.
  8.  
  9. Remove the drive belts. Remove the attaching bolts, then remove the cam cover and gasket.
  10.  



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Fig. Fig. 28: Turn the crankshaft (on the injection pump end of the engine) clockwise until the timing marks align, then turn it an additional 45 degrees. In this position, the work can be performed on the diesel engine without risking piston or valve damage



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Fig. Fig. 29: Loosen the timing belt tensioner lockbolt, depress the belt as shown, then retighten the lockbolt-diesel engine



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Fig. Fig. 30: Cylinder head bolt loosening sequence-diesel engine



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Fig. Fig. 31: Cylinder head bolt torque sequence-diesel engine

  1. Remove the rear timing belt. For details, refer to the timing belt procedure later in this section.
  2.  
  3. Put an open-end wrench on the flats of the camshaft to keep it from turning and loosen the camshaft rear pulley mounting bolt. Then, remove the pulley with a puller.
  4.  
  5. Screw two M8 x 1.25 x 45mm bolts into the rear seal plate so they pass through the two holes in the injection pump drive pulley. Remove the pulley lockbolt, then remove the affixing bolts, pulley and Woodruff key.
  6.  
  7. Remove the tensioner, spring and lockbolt from the rear timing belt mechanism. Then, remove the rear seal plate.
  8.  
  9. Remove the right timing belt cover from the front timing belt mechanism. Remove the top bolt from the left timing belt cover.
  10.  
  11. Turn the crankshaft to align the mark on the front camshaft pulley with the mark on the front seal plate. Then, turn the crankshaft 45 degrees ahead, as shown.
  12.  
  13. Loosen the tensioner lockbolt, and depress the timing belt toward the center of the engine. Hold the belt in the depressed position, then retighten the lockbolt.
  14.  
  15. Install a wrench onto the camshaft pulley, then turn the pulley gently counterclockwise and hold it there, in order to make belt removal easier. Remove the belt.
  16.  
  17. Install a large, open-end wrench onto the camshaft flats, then loosen the camshaft front pulley mounting bolt. Remove the pulley with a puller. Discard the pulley lockbolt, as it must be replaced with a new one when the pulley is reinstalled.
  18.  

Do not attempt to hammer the pulley or camshaft to remove the pulley.

  1. Remove the front seal lockplate bolts, then remove the lockplate and seals. For details on seal removal, refer to the camshaft procedure later in this section.
  2.  
  3. If you will probably be working on the valves or prechambers, remove the camshaft cap bolts and the camshaft at this time (see the appropriate procedure, later in this section). Otherwise, remove the cylinder head mounting bolts in several stages, turning them a little at a time in the indicated order. Remove the cylinder head.
  4.  
  5. Thoroughly clean the cylinder head and engine block mating surfaces, then inspect the components for warping or other damage, as described later in this section. If distortion of the head surface which mates with the block exceeds the limit, replace the head. If distortion of either manifold contact surface exceeds the limit, grind or replace the head. Repair or replace other parts, such as cylinder head bolts, as necessary.
  6.  

To install:
  1. Position a new head gasket onto the block. Make sure the crankshaft is still positioned as described in Step 10. Then, position the cylinder head onto the block.
  2.  
  3. Measure the length of every head bolt from the lower surface of the cap to the lower end of the bolt. If the length exceeds 4.5079 in. (114.5mm), replace the bolt. Lubricate the threads on all the bolts you are going to use with engine oil.
  4.  
  5. Install the bolts finger-tight.
  6.  
  7. Torque the head bolts to 22 ft. lbs. (29 Nm) in the numbered sequence. Paint or punch a mark on the outer surface of the bolt head. Then, in the same sequence, turn each bolt 90-105 degrees. When this is completed, turn each bolt in the same sequence another 90-105 degrees.
  8.  

The double tightening of each cylinder head bolt by 90-105 degrees is to secure the uniform force load on the head gasket. If not done properly, air-tightness of the cylinders may be insufficient.

  1. If applicable, install the camshaft. Install the front and rear camshaft oil seals by first oiling the lips of the seals with clean engine oil, then install them by pressing on either side with your thumbs. Note that the rear seal is just slightly larger.
  2.  
  3. Install the front camshaft pulley with its Woodruff key onto the camshaft. Hold the camshaft in position, using a wrench on the flats, then install a new pulley lockbolt, torquing it to 41-48 ft. lbs. (56-65 Nm). Turn the camshaft to align the mark on the pulley with the mark on the front seal plate (at about 2 o'clock).
  4.  
  5. Remove the cover for the inspection hole from the clutch housing. Then, turn the crankshaft back to Top Dead Center (TDC), as marked on the flywheel.
  6.  
  7. Install and adjust the timing belt. For details, refer to the timing belt procedure found later in this section. Install the top bolt for the left side belt cover (removed in Step 9). Install the right side timing belt cover.
  8.  
  9. Install the rear seal plate. Install the fuel injection pump pulley with its Woodruff key. Then, rotate the pulley until the mark on the pulley aligns with the mark on the rear seal plate. Install the two bolts used in removal, then install the pulley bolt and torque it to 43-51 ft. lbs. (58-69 Nm). Leave the affixing bolts in place until the rear timing belt has been installed.
  10.  
  11. Install the rear camshaft pulley and Woodruff key onto the camshaft. Hold the camshaft in place, using a wrench on the flats, and install the lockbolt, torquing to 41-48 ft. lbs. (56-65 Nm).
  12.  
  13. Install the tensioner, spring and lockbolt in the fully loosened position. Rotate the tensioner clockwise as far as it will go, then temporarily tighten it.
  14.  
  15. Install and tension the rear timing belt as described under Rear Timing Belt Removal and Installation, later in this section.
  16.  
  17. Remove the affixing bolts from the fuel injection pump pulley.
  18.  
  19. Check the valve clearance and adjust as necessary, using the appropriate procedure in Engine Electrical .
  20.  
  21. Perform the remaining steps in reverse of the removal procedure.
  22.  
  23. Start the engine and check for leaks. Perform any necessary adjustments.
  24.  

CLEANING AND INSPECTION



See Figures 32, 33, 34, 35, 36, 37, 38, 39, 40, 41 and 42

  1. Thoroughly clean the cylinder head and cylinder block contact surfaces to remove any dirt, oil or old gasket material.
  2.  



Click image to see an enlarged view

Fig. Fig. 32: Use a gasket scraper to remove the bulk of the old head gasket from the cylinder head's mating surface

  1. Check the cylinder head for distortion in six planes, as shown, by placing a straightedge horizontally and diagonally across the cylinder head, and across each end, while attempting to insert a feeler gauge between the head surface and the straightedge. The permissible limit is 0.006 in. (0.15mm) for 4-cylinder gasoline engines or 0.004 in. (0.10mm) for 6-cylinder and diesel engines.
  2.  

If distortion exceeds the limit, measure the cylinder head height. If the height is within specifications, based on the following figures, resurface (grind) the cylinder head surface (except diesel engines) or replace it. If a diesel engine cylinder head's distortion exceeds the limit, replace the head.



1978-85 GLC: 3.551-3.560 in. (90.3-90.5mm)
 
1986-89 323: 4.228-4.236 in. (107.40-107.60mm)
 
1979-82 626: 4.289-4.293 in. (108.95-109.05mm)
 
1983-89 626/MX-6: 3.620-3.624 in. (91.95-92.05mm)
 
1988-89 929: 4.931-4.935 in. (125.25-125.35mm)
 



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Fig. Fig. 33: An electric drill equipped with a wire wheel will expedite complete gasket removal



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Fig. Fig. 34: Check the cylinder head for distortion by using a straightedge and feeler gauge along six planes of the block mating surface (as indicated by the straight lines)-4-cylinder gasoline engine

As long as the specified minimum height is maintained, a cylinder head may be ground up to the appropriate maximum amount, as follows:



1978-85 GLC: 0.008 in. (0.20mm)
 
1986-89 323: 0.008 in. (0.20mm)
 
1979-82 626: 0.008 in. (0.20mm)
 
1983-89 626/MX-6 (except diesel): 0.008 in. (0.20mm)
 
1988-89 929: 0.006 in. (0.15mm)
 

  1. On 1979-82 engines, also check the intake and exhaust manifold mating surfaces for distortion by placing a straightedge horizontally across the manifold, while attempting to insert a feeler gauge between the manifold surface and the straightedge. The permissible limit is 0.006 in. (0.15mm). If excessive distortion is detected, grind or replace the manifold.
  2.  



Click image to see an enlarged view

Fig. Fig. 35: The cylinder heads on 6-cylinder gasoline engines should also be checked for warpage across 6 planes



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Fig. Fig. 36: Check the diesel cylinder head for distortion in the same manner as for gasoline engines



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Fig. Fig. 37: When checking for warpage be sure to use a precision straightedge and a feeler gauge



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Fig. Fig. 38: Check for warpage at all angles, not just one or two of them



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Fig. Fig. 39: Check the cylinder head's intake and exhaust manifold contact surfaces for distortion in three planes each-1988-89 4-cylinder engine

  1. On diesel engines and 1988-89 gasoline engines, also check the cylinder head's intake and exhaust manifold contact surfaces for distortion in three planes each, as shown. Do this by placing a straightedge across the contact surface, while attempting to insert a feeler gauge between the surface and the straightedge. Repeat for the opposite side. The limit is 0.006 in. (0.15mm) for 4-cylinder gasoline engines, 0.004 in. (0.10mm) for 6-cylinder engines, or 0.008 in. (0.20mm) for diesel engines.
  2.  

If distortion exceeds the limit, grind (resurface) the cylinder head contact surface or replace it.

  1. Inspect the cylinder head's water passages to make sure they are fully open. If necessary, hot tank the head in a solution that is compatible with aluminum to clean the passages.
  2.  
  3. Inspect the cylinder head bolts for damaged threads and make sure they are free from grease and dirt. Repair or replace any damaged threads or broken studs.
  4.  



Click image to see an enlarged view

Fig. Fig. 40: Again, the cylinder heads on 1988-89 6-cylinder engines should be checked along 3 planes for each of the manifold mating surfaces



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Fig. Fig. 41: Check the diesel engine cylinder head's manifold contact surfaces in the same manner as for gasoline engines



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Fig. Fig. 42: Before installing the cylinder head, be sure to also remove old gasket material from the engine block

RESURFACING



Due to the special equipment and required precision, it is recommended that cylinder head regrinding only be performed by an experienced and reputable machine shop.

 
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