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4.8 Removing and Installing Cylinder Head

The cylinder head can be removed without removing the engine from the vehicle, and without removing the camshaft(s). On diesel and 16-valve engines, new cylinder head bolts should be used every time the cylinder head is installed.

If a failed head gasket or warped head is suspected, a compression test, as described in 3.2 Diagnostic Testing, may aid diagnosis and should be performed before the cylinder head is removed. A failed head gasket may be caused by a warped cylinder head. When replacing a failed head gasket, always check the cylinder head for straightness. Specifications for maximum permissible warpage can be found in 4.9 Disassembly, Assembly, and Reconditioning.

To remove cylinder head:
1. Disconnect the battery negative (-) terminal from the battery. Disconnect the ground strap from the cylinder head or intake manifold.
2. On gasoline engines, disconnect the intake air duct from the throttle body on the intake manifold.
3. On diesel engines, remove the air cleaner and the intake air duct. On turbo diesel engines, remove the turbocharger as described in EXHAUST SYSTEM AND EMISSION CONTROLS.
4. Drain the coolant as described in COOLING SYSTEM.
5. Remove the camshaft drive belt. For gasoline engines, see 4.2 Camshaft Drive Belt. For diesel engines, see FUEL SYSTEM-DIESEL.
6. On diesel engines only, disconnect the accelerator cable and the fuel injection pipes as described in FUEL SYSTEM-DIESEL. Disconnect the wire from the glow plug bus.
7. On gasoline engines, pull out the fuel injectors and remove the cold start valve from the intake manifold, leaving the fuel lines attached. Cover the injectors and the cold start valve to keep them clean, and plug the openings. Disconnect the throttle cable and throttle switches from the throttle body. Disconnect and label the hoses and wires connected to the throttle body and the intake manifold. For more information on fuel injection components, see FUEL SYSTEM-GASOLINE.
8. Disconnect the exhaust pipe from the exhaust manifold, as described in EXHAUST SYSTEM AND EMISSION CONTROLS.
9. Loosen the alternator mounting bolts and remove the upper alternator mounting bracket.
10. Disconnect the coolant hoses from the outlet on the front of the cylinder head and from the heater outlet on the left (driver's side) end of the cylinder head. Disconnect the wires from the temperature and oil pressure sending units, and label them.
11. On gasoline engines, disconnect the spark plug connectors from the spark plugs. On 16-valve engines, also disconnect the high voltage lead from the coil, and then remove the distributor as described in IGNITION.
12. Remove the cylinder head cover, and the upper intake manifold on 16-valve engines, as described in 4.1 Cylinder Head Cover and Gasket.
13. Gradually and evenly loosen the cylinder head bolts, beginning with the outer bolts and working toward the center, and remove the cylinder head. If the head is stuck, use a soft-faced mallet or pry gently with a wooden stick to loosen it.

To install cylinder head:
1. Clean the cylinder head and the gasket surface of the cylinder block. Clean the threads of the head bolts and bolt holes with thread chasers, and remove all foreign matter from the holes. Avoid letting debris into the cylinders or oil passages in the cylinder block.


Do not use a metal scraper or wire brush to clean the aluminum cylinder head. These may damage the cylinder head. Instead, use a solvent to soften carbon deposits and old sealing materials. If necessary, use a wooden or plastic scraper.

2. Check the gasket surfaces of the cylinder head and the cylinder block for warpage. See 4.9 Disassembly, Assembly, and Reconditioning.
3. On diesel engines, reinstall the combustion pre-chamber inserts, if they were removed while cleaning the cylinder head.
4. Place a new cylinder head gasket on the surface of the cylinder block. The word "OBEN", found imprinted on the gasket near the part number, should face up.


Cylinder head gaskets will give a reliable seal only once. Always use a new gasket that has not previously been compressed by tightening the cylinder head bolts.


Three different cylinder head gaskets are available for use on diesel engines, identified by a number of notches or holes in the gasket near the part number. When reassembling the same cylinder head and cylinder block, make sure that the new gasket matches the one it replaces. When assembling a new cylinder head, a new cylinder block, or an overhauled cylinder block, the correct gasket must be selected by measuring piston protrusion. See 6. Cylinder Block and Pistons.

5. On diesel engines, position the crankshaft to the TDC marking. Then turn the crankshaft opposite engine rotation until all pistons are at nearly equal height.
6. Place the cylinder head in position on the cylinder block. Loosely install all the head bolts, with the special washers, then thread them in until they are finger-tight.


To be sure of proper alignment of the installed cylinder head, place two 200 mm long, 9 mm diameter (8 in. x 3/8 in.) wooden dowels into two of the outermost head bolt holes to hold the gasket and serve as guides as the cylinder head is installed. Thread in several bolts, then remove the dowels and install the remaining bolts.

7. Torque the bolts to 40 Nm (30 ft. lb.), in the sequence shown in Fig. 4-19. Repeat the sequence, torquing the bolts to 60 Nm (44 ft. lb.). Repeat the sequence a third time, tightening each bolt an additional 1/2 turn. Alternatively, this last step may be done as two 1/4 turns.

Fig. 4-19. Cylinder head bolt tightening sequence for all gasoline and diesel engines.


On diesel and 16-valve gasoline engines, the head bolts are designed to be used only once. Always replace them with new head bolts when removing cylinder head.

8. Installation of the remaining parts is the reverse of removal. See 4.2 Camshaft Drive Belt, 4.1 Cylinder Head Cover and Gasket, FUEL SYSTEM-DIESEL, FUEL SYSTEM-GASOLINE, and EXHAUST SYSTEM AND EMISSION CONTROLS. For installation of the ignition distributor on 16-valve engines, see IGNITION.
9. Refill the cooling system as described in COOLING SYSTEM.
10. On diesel engines, run the engine until it reaches normal operating temperature. Retorque the cylinder head bolts in sequence 1/4 turn without loosening. For engine codes ME and MF only, after appx. 1000 miles, retorque the cylinder head bolts an additional 1/4 turn, without loosening and without interruption.

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