Saturday, December 10, 2011

How to Replace Camshaft, Bearings and Lifters on Toyota Previa ?

The Cam Shaft is a  shaft having lobes driven by the crankshaft via gears, chains, or belts that, in turn, opens and closes the intake and exhaust valves at proper.Most camshaft bearings are made from seamless steel tubing with lining material bonded to the inside. Heavy-duty cam bearings are made in flat strips. The layer, or layers, of lining material are bonded to the strip, and the strip is rolled to form the bearing. The seam will be either interlocking or straight.
The details to remove Camshaft are as follows :----

REMOVAL & INSTALLATION



See Figures 1 through 31
  1. Disconnect the negative battery cable. Wait at least 90 seconds before performing any work after the cable has been disconnected on models 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 .

  1. Relieve the fuel system pressure.

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.

  1. Remove the engine wiring from the engine and move it aside.
  2. Remove the No. 2 valve cover.
  3. Mark the spark plug wires and disconnect. Matchmark the distributor, rotor and cylinder head. Remove the distributor and disconnect the wiring.
  4. Remove the PCV hose.
  5. Remove the No. 1 valve cover and two half circular plugs.


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Fig. Fig. 1: Remove the half circular plugs (half-moons) from the side of the head
  1. Remove the chain tensioner and gasket.


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Fig. Fig. 2: Remove these bolts to access the tensioner


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Fig. Fig. 3: Pull the tensioner out of the engine in the upright position, do not turn it upside down
  1. Place matchmarks on the timing sprocket and chain. Hold the intake camshaft with a wrench and remove the sprocket bolt.


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Fig. Fig. 4: Place matchmarks on the camshaft timing gear and chain before removal


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Fig. Fig. 5: Hold the intake camshaft with a wrench and remove the bolt


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Fig. Fig. 6: Be sure to place the wrench on a portion of the camshaft where it will not be damaged


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Fig. Fig. 7: The sprocket bolt is a large headed bolt on the front of the cam
It is a good idea to tie the chain and sprocket together with a tie rap.


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Fig. Fig. 8: Place a tie rap around the cam sprocket and chain to secure them
  1. Remove the cam sprocket and chain from the camshaft and leave on the slipper and damper.


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Fig. Fig. 9: Remove the cam sprocket and chain as an assembly
Be sure not to remove the slipper and damper. Since the thrust clearance of the camshaft is small, the camshaft must be kept level while it is being removed. If the camshaft is not kept level, the portion of the cylinder head receiving the shaft thrust may crack or be damaged, causing the camshaft to seize or break. To avoid this, follow the steps carefully.
  1. To remove exhaust camshaft:
    1. Set the knock pin hole of the exhaust camshaft at the 5-30 degree BTDC of camshaft angle.
The above angle helps to lift the exhaust camshaft level and evenly by pushing No. 2 and No. 4 cylinder cam lobes of the exhaust camshaft to their valve lifters.
  1. Secure the exhaust camshaft sub-gear to main gear with a service bolt. The recommended size bolt is 0.63-0.79 inch (16-20mm) bolt length, 6mm thread diameter and 1.0mm thread pitch.
When removing the camshaft, make sure that the torsional spring force of the sub-gear has been eliminated by the previous step.
  1. Uniformly loosen the 8 bolts on the No. 1, No. 2, No. 3 and No. 5 bearing caps in several passes in the proper sequence.
Do not remove No. 4 bearing cap bolt at this stage.
  1. Remove the No. 1, No. 2, No. 3 and No. 5 bearing caps.
  2. Alternately loosen No. 4 bearing cap. As No. 4 bearing cap bolts are loosened, check that the camshaft is being lifted out straight and level.
If the camshaft is not being lifted out straight and level, retighten the 2 No. 4 bearing cap bolts. Repeat steps, in order, (e) to (a) and reset the knock pin hole of the exhaust camshaft at 5-30°BTDC, then repeat steps (b) to (e) again. Do not pry or attempt to force the camshaft with a tool or another object.
  1. Remove the No. 4 bearing cap and exhaust camshaft.


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Fig. Fig. 10: Set knock pin hole of exhaust camshaft at 5-30 degrees BTDC of camshaft angle


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Fig. Fig. 11: Secure exhaust camshaft sub-gear to main gear with service bolt


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Fig. Fig. 12: A service bolt should be the correct size to fit in the hole of the gear


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Fig. Fig. 13: Remove No. 1, 2, 3 and 5 bearing caps (exhaust camshaft) in sequence shown


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Fig. Fig. 14: Loosening the No. 3 exhaust camshaft bearing cap bolts


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Fig. Fig. 15: Removing the No. 1 exhaust camshaft bearing


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Fig. Fig. 16: Alternately loosen and remove the bolts on the No. 4 bearing cap last


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Fig. Fig. 17: The No. 4 exhaust camshaft bearing is always removed last


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Fig. Fig. 18: Now the exhaust camshaft can be pulled out of the head
Remember, the head is on the engine sideways and the camshaft can fall out if you are not careful. Hold on to the camshaft while removing the No. 4 bearing.
  1. To remove the intake camshaft:
    1. Set the knock pin hole of the intake camshaft at the 75-100 degree BTDC of camshaft angle.
The above angle allows the no. 1 and No. 3 cylinder cam lobes of the intake camshaft to push their valve lifters evenly.
  1. Uniformly loosen the 8 bolts on the No. 1, No. 2, No. 4 and No. 5 bearing caps in several passes in the proper sequence.
Do not remove No. 3 bearing cap bolt at this stage.
  1. Remove the No. 1, No. 2, No. 4 and No. 5 bearing caps.
  2. Alternately loosen No. 3 bearing cap. As No. 3 bearing cap bolts are loosened, check that the camshaft is being lifted out straight and level.
If the camshaft is not being lifted out straight and level, retighten the 2 No. 3 bearing cap bolts. Repeat step, in order from (d) to (a) and reset the knock pin of the intake camshaft at 75-100°BTDC, and repeat steps in order from (b) to (d) once again. Do not pry or attempt to force the camshaft with a tool or other object.
  1. Remove the No. 3 bearing cap and the intake camshaft.


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Fig. Fig. 19: Set knock pin of intake camshaft at 75-100 degrees BTDC of camshaft angle


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Fig. Fig. 20: Remove No. 1, 2, 4 and 5 bearing caps (intake camshaft) in sequence shown


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Fig. Fig. 21: Uniformly loosen and remove the intake camshaft bearing cap bolts


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Fig. Fig. 22: Remove the No. 3 intake camshaft bearing cap last


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Fig. Fig. 23: The intake camshaft can fall out if not grabbed quickly
  1. Remove the valve lifters from the engine. Keep the shims and the lifters together. The lifters and the shims must be reinstalled in their original location.


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Fig. Fig. 24: Remove the lifters and shims together from the cylinder head


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Fig. Fig. 25: The shims and lifters are located in the head
To install:
If any of the bolts break, deform or do not meet the tighten specification replace them.
  1. Install the valve lifters and shims.
  2. Install the intake camshaft:
    1. Apply MP grease to the thrust portion of the intake camshaft.
    2. Place the intake camshaft at 75-100 degrees BTDC. Install the bearing caps with the marking arrows facing forward. Uniformly tighten the bearing cap bolts in several passes in the proper sequence to 12 ft. lbs. (16 Nm).


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Fig. Fig. 26: Place the intake camshaft at 75-100°BTDC of the camshaft angle on the head


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Fig. Fig. 27: Camshaft bearing cap bolts tightening sequence; intake and exhaust are the same
  1. Install the exhaust camshaft:
    1. Set the knock pin of the intake camshaft at 5-30 degrees BTDC of camshaft angle.
    2. Apply MP grease to the thrust portion of the exhaust camshaft.
    3. Engage the exhaust camshaft gear to the intake camshaft gear by matching the installation marks (timing marks).
    4. Roll down the exhaust camshaft onto the bearing journals while engaging the gears with each other. Make sure the exhaust and intake camshaft gear alignment marks are facing each other. The one gear has 2 dots and the other has 1 dot.
    5. Install the bearing caps with the marking arrows facing forward.
    6. Uniformly tighten the bearing cap bolts in several passes in the proper sequence to 12 ft. lbs. (16 Nm).


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Fig. Fig. 28: Set the knock pin of the intake camshaft at 5-30°BTDC of the camshaft angle


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Fig. Fig. 29: Engage the exhaust and intake camshafts by matching the timing marks to each gear


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Fig. Fig. 30: Install and uniformly tighten the 10 bearing cap bolts in several passes in this sequence
  1. Apply sealer to the bottom of No. 6 bearing cap and install. Tighten the cap to 12 ft. lbs. (16 Nm).


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Fig. Fig. 31: Apply adhesive to the No. 6 bearing cap
  1. Install the camshaft sprocket and chain. Hold the camshaft with a wrench and tighten the bolt to 54 ft. lbs. (74 Nm).


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Fig. Fig. 32: Retain the camshaft and tighten the bolt
  1. Release the chain tensioner ratchet pawl. Fully push in the plunger and apply the hook to the pin so the plunger can not spring out and install the tensioner. Tighten the bolts to 15 ft. lbs. (21 Nm).


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Fig. Fig. 33: The tensioner has a hook to hold the plunger in the down position


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Fig. Fig. 34: Push the plunger in and position the hook over the pin
  1. Set the tensioner: Turn the crankshaft to the left so the hook of the tensioner is released from the pin. If it does not spring out, press the slipper into the tensioner to release the hook.
  2. Adjust the valve clearance.
  3. Apply sealant 08826-00080 or equivalent to the cylinder head. Install the 2 half-circular plugs to the cylinder head and install the valve cover. Tighten the bolts to 69 inch lbs. (8 Nm).
  4. Install the PCV hose.
  5. Install the distributor.
  6. Install the No. 2 cylinder head cover.
  7. Install the engine wire and connect all connectors.
  8. Install the engine/transmission assembly into the vehicle.
  9. Fill the cooling system. Fill the engine with oil.
  10. Connect the battery cable. Start the engine and check for leaks.
  11. Road test the vehicle for proper operation. Recheck all fluid levels.

INSPECTION



Runout
See Figure 35
  1. Place the camshaft on V-blocks.
  2. Using a dial indicator, measure the circle runout at the center journal. Maximum circle runout is 0.0024 inch (0.06mm). If the runout is greater than maximum, replace the camshaft.


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Fig. Fig. 35: Use a dial indicator to measure circle runout of the camshaft
Lobe Height
See Figure 36
  1. Using a micrometer, measure the cam lobe height. Standard cam lobe height:

    2TZ-FE Intake-1.7839-1.7878 inch (45.31-45.41mm)
    2TZ-FZE Intake-1.7720-1.7760 inch (45.01-45.11mm)
    Exhaust-1.7740-1.7779 inch (45.06-45.16mm)
  2. If the cam lobe height is less than minimum, replace the camshaft.


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Fig. Fig. 36: Place a micrometer over the cam lobe and measure the height, if less than minimum, replace the camshaft
Journals
See Figure 37
  1. Using a micrometer, measure the journal diameter. Standard diameter is 1.0614-1.0620 inch (26.959-26.975mm). If the diameter is not as specified, check the oil clearance.


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Fig. Fig. 37: Use a micrometer to measure the journal diameter of the camshaft
Bearings
See Figure 38
  1. Check the bearings for flaking and scoring. If the bearings seem to be damaged, replace the caps and cylinder head as a set.


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Fig. Fig. 38: Check the bearings for flaking and scoring
Journal Oil Clearance
See Figures 39 and 40
  1. Clean the bearing caps and camshaft journals.
  2. Place the camshafts on the cylinder head.
  3. Lay a strip of Plastigage® across each camshaft journal.
  4. Install the bearing caps and tighten to 12 ft. lbs. (15 Nm). Do not turn the camshaft.
  5. Remove the bearing caps.
  6. Measure the Plastigage® at its widest point. Standard oil clearance is 0.0010-0.0024 inch (0.025-0.062mm). Maximum oil clearance is 0.0031 inch (0.08mm). If the oil clearance is greater than maximum, replace the camshaft. If necessary, replace the bearing caps and cylinder head as a set.
  7. Completerly remove the gauge material.


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Fig. Fig. 39: Place the gauging material across the camshaft journals ...


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Fig. Fig. 40: ... then measure it at its widest point
Thrust Clearance
See Figure 41
  1. Install the camshaft.
  2. Using a dial indicator, measure the thrust clearance while moving the camshaft back and forth.

    Standard thrust clearance-0.0016-0.0037 inch
    Maximum thrust clearance-0.0047 inch (0.12mm)
  3. If the thrust clearance is greater than maximum, replace the camshaft. If necessary, replace the bearing caps and cylinder head as a set.


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Fig. Fig. 41: Place a dial indicator at the end of the camshaft as shown and measure the thrust clearance
Camshaft Gear Backlash
See Figure 42
  1. Install the camshafts without installing the exhaust cam sub-gear.
  2. Using a dial indicator, measure the gear backlash.

    Standard backlash-0.0008-0.0079 inch (0.020-0.200mm)
    Maximum backlash-0.0118 inch (0.30mm)
  3. If the backlash is greater than maximum, replace the camshafts.


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Fig. Fig. 42: Place a dial indicator on the camshaft gear and measure the gear backlash
Camshaft Gear Spring
See Figure 43
  1. Using a venire caliper, measure the free distance between the spring ends. The distance should be between 0.886-0.902 inch (22.5-22.9mm). If the free distance is not as specified, replace the gear spring.


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Fig. Fig. 43: The free distance is measure in between the two spring ends
Valve Lifters and Lifter Bores
See Figures 44 and 45
  1. Using a caliper gage, measure the lifter bore diameter of the cylinder head. Standard lifter bore diameter is 1.2205-1.2211 inch (31.000-31.016mm).


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Fig. Fig. 44: Insert a caliper gage into the lifter bore and measure the diameter
  1. Using a micrometer, measure the lifter diameter. Standard diameter is 1.2191-1.2195 inch 930.966-30.976mm).


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Fig. Fig. 45: A micrometer will measure the outside lifter diameter
  1. Subtract the lifter diameter measurement from the lifter bore diameter measurement.

    Standard oil clearance-0.0009-0.0020 inch (0.024-0.050mm)
    Maximum oil clearance-0.0028 inch (0.07mm)
  2. If the oil clearance is greater than maximum, replace the lifter. If necessary, replace the cylinder head.

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This basic details will help.Thanks.
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If you need dis-assembly or replacement instructions for any other auto/car part, or you want to ask question related to your car/truck jeep problem then please leave the comment with your details, so I can provide you the required instructions and solutions.

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For more Toyota Previa parts removal,check the list below :----

How to Remove Exhaust Manifold on Toyota Previa?


How to Remove Intake Manifold on Toyota Previa?


How to Remove Timing Chain Cover and Seal on Toyota Previa?


How to Remove Timing Chain and Gears on Toyota Previa?


How to Remove Cylinder Head on Toyota Previa?


How to Remove Engine on Toyota Previa?


How to Remove Water Pump on Toyota Previa?




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