How to Remove Cylinder Head on Toyota Previa?

Its very time consuming job.Requires proper knowledge and appropriate tools.
The details to perform this task is as follows :-----

REMOVAL & INSTALLATION

Engine Installed

See Figures 1 through 10

1. Drain the engine cooling system.

To access and remove the cylinder head, the engine must be lowered and the both motor mounts removed.

2. Remove the left and right engine access hole covers.
3. Remove the motor mount bolts and nuts.

Fig. Fig. 1: Loosen and remove the upper mount nut

Fig. Fig. 2: Next remove the motor mount lower retaining nut and bolt

4. Raise the engine and remove the motor mounts.

Fig. Fig. 3: Slide the mount out from between the members

5. Slowly lower the engine being careful not to rest the engine weight on the oil filter housing. Place a block of wood where the motor mounts had been to support the engine.
6. Remove the exhaust manifold .
7. Remove the distributor.
8. Disconnect the EGR pipe bracket-to-intake manifold bolt. This bolt can be reached from the right hand access hole. Follow the EGR pipe from the cylinder head back until you find the bracket and bolt.
9. Remove the nut and bolt holding the EGR pipe to the cylinder head.
10. Disconnect the engine wiring harness and fuel connections for the cylinder head. Remove the fuel rail with injectors.
11. Unbolt and disconnect the two cylinder head and water neck brackets from the forward end of the head.
12. Remove the lower intake manifold support bracket.
13. From the left engine access hole, remove the two upper intake manifold bracket bolts.
14. Remove the intake manifold-to-cylinder head hardware, then break the manifold free from the head.
15. Remove the water neck mounting bolts and loosen the water neck from the cylinder head.
16. Remove the spark plug cover, plug wires, and valve cover.
17. Remove the camshafts. Refer to the Camshaft Removal and Installation procedure in this section.
18. Place a jack under the cylinder head with a block of wood between them. Remove the cylinder head bolts.

Make sure you remove the two front bolts first in the timing chain area.

19. Remove the two bolts in front of the head before the other head bolts are removed. The two bolts are located in front of the timing chain.
20. Uniformly remove the head bolts following the sequence.

The cylinder head is positioned on the engine sideways and is very heavy. Be careful not to drop the head during removal. It is advised to have an assistant ready to help.

21. Pull the cylinder head from the dowels on the cylinder block.
22. Remove the cylinder head gasket.

Fig. Fig. 4: Cylinder head bolt loosing sequence

To install:

Always clean and inspect the cylinder head and mating surface for cracks and flatness when removed.

23. Clean the gasket mating surfaces and check for warpage.
24. Apply seal packing to two locations on the cylinder block as shown.

Fig. Fig. 5: Apply seal packing in these two areas on the block

25. Install the head gasket and cylinder head.

Fig. Fig. 6: Place the head gasket in the correct position on the block

26. If the camshaft timing gear was removed, align the matchmarks placed on the timing gear and chain during removal.
27. Place the cylinder head in position on the gasket.
28. Oil the bolts and using the proper sequence, tighten the bolts in 3 steps.
    1. Uniformly tighten the head bolts to 29 ft. lbs. (39 Nm).
    2. Mark the front of the cylinder head bolt with paint.
    3. Retighten the cylinder head bolts 90° in the numerical order as shown.
    4. Check that the painted mark is now facing sideward.
    5. Retighten the cylinder head bolts an additional 90°.
    6. Check that the painted mark is now facing rearward.
       
       
       

       

       Fig. Fig. 7: Tightening specifications can be found on a label located on the No. 2 cylinder head cover
       
       
       
       

       

       Fig. Fig. 8: Cylinder head bolt tightening sequence
       
       
       
       

       

       Fig. Fig. 9: Mark the front of the head bolt with paint
       
       
       
       

       

       Fig. Fig. 10: Retighten the head bolts 90° in the order shown
29. Install and tighten the 2 front mounting bolts to 15 ft. lbs. (21 Nm).
30. Install the camshafts.
31. Install all remaining components.
32. Fill the cooling system and fill the engine with oil.
33. Connect the battery cable, start the engine, and check for leaks.
34. Road test the vehicle for proper operation and recheck all fluid levels.

Engine Removed

See Figures 4 through 21

1. Disconnect the negative battery cable. Wait at least 90 seconds when working on vehicles equipped with an airbag.

CAUTION

Some models covered by this guide may be equipped with a Supplemental Restraint System (SRS), which uses an air bag. Whenever working near any of the SRS components, such as the impact sensors, the air bag module, steering column and instrument panel, disable the SRS, as described in Chassis Electrical .

2. Relieve the fuel system pressure.

Fig. Fig. 11: Exploded view of the cylinder head removal components

Fig. Fig. 12: Exploded view of the cylinder head removal components (continued)

Fig. Fig. 13: Exploded view of the cylinder head removal components (continued)

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.

3. Remove the engine/transmission assembly from the vehicle.
4. Label and remove the engine wiring from the engine and move it aside.

Fig. Fig. 14: Unbolt and remove the engine wire

5. Unbolt and remove the No. 2 head cover.
6. Remove the distributor.
7. Remove the EGR valve.
8. Remnove the union bolts and gaskets from the delivery pipe and cold start injector. Unbolt and remove the pressure regulator with the hose from the delivery pipe. Unbolt and extract the delivery pipe.
9. Disconnect the hose and unbolt then extract the water outlet from the engine.

Fig. Fig. 15: Unbolt and remove the water outlet from the engine

10. Remove the PCV hose.
11. Remove the fuel delivery pipe with insulators.

Fig. Fig. 16: Remove these bolts to separate the fuel pipe from the engine

12. Remove the intake manifold.
13. Remove the right side engine mounting.

Fig. Fig. 17: Remove these three bolts to extract the right side insulator

14. Remove the exhaust manifold and heat insulator.
15. Remove the No. 1 oil return pipe.

Fig. Fig. 18: The No. 1 oil return pipe is retained with two bolts

16. Remove the No. 1 cylinder head cover and half moons.
17. See the procedure under Camshaft Removal and Installation and remove the camshafts.
18. Remove the 2 bolts in front of the head before the other head bolts are removed.

Fig. Fig. 19: Remove these two bolts in the front of the head before the others

19. Using a 12 sided socket wrench, remove the 10 cylinder head retaining bolts in the proper sequence.

20. Remove the cylinder head from the block as follows:
    1. Remove the two bolts in front of the head before the other head bolts are removed. The two bolts are located in front of the timing chain.
    2. Uniformly remove the 10 head bolts in the reverse of the torque sequence.
    3. Pull the cylinder head from the dowels on the cylinder block.
    4. If the head is difficult to remove, pry with a suitable tool between the head and block surfaces
    5. Remove the cylinder head gasket.

To install:

Always clean and inspect the cylinder head and mating surface for cracks and flatness when removed.

21. Clean the gasket mating surfaces and check for warpage.
22. Apply seal packing to two locations on the cylinder block as shown.

Fig. Fig. 20: Apply seal packing in these two areas on the block

23. Install the head gasket and cylinder head.

Fig. Fig. 21: Place the head gasket in the correct position on the block

24. If the camshaft timing gear was removed, align the matchmarks placed on the timing gear and chain during removal.
25. Place the cylinder head in position on the gasket.
26. Oil the bolts and using the proper sequence, tighten the bolts in 3 steps.
    1. Uniformly tighten the head bolts to 29 ft. lbs. (39 Nm).
    2. Mark the front of the cylinder head bolt with paint.
    3. Retighten the cylinder head bolts 90° in the numerical order as shown.
    4. Check that the painted mark is now facing sideward.
    5. Retighten the cylinder head bolts an additional 90°.
    6. Check that the painted mark is now facing rearward.
27. Install and tighten the 2 front mounting bolts to 15 ft. lbs. (21 Nm).
28. See the procedure under Camshaft Removal and Installation and install the camshafts.
29. Install all remaining components.
30. Install the engine/transmission assembly into the vehicle.
31. Fill the cooling system and fill the engine with oil.
32. Connect the battery cable, start the engine, and check for leaks.
33. Road test the vehicle for proper operation and recheck all fluid levels.

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This basic details will help.Thanks.

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