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    2000 Lexus SC300 3.0L SFI DOHC 6cyl

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    Lexus GS, SC 1998-06

    Timing Belt

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    General Information



    Timing belts are typically only used on overhead camshaft engines. Timing belts are used to synchronize the crankshaft with the camshaft, similar to a timing chain on an overhead valve (pushrod) engine. Unlike a timing belt, a timing chain will normally last the life of the engine without needing service or replacement. Timing belts use raised teeth to mesh with sprockets to operate the valvetrain of an overhead camshaft engine.

    Whenever a vehicle with an unknown service history comes into your repair facility or is recently purchased, here are some points that should be asked to help prevent costly engine damage:



    Does the owner know if, or when the belt was replaced-
     
    If the vehicle purchased is used, or the condition and mileage of the last timing belt replacement are unknown, it is recommended to inspect, replace or at least inform the owner that the vehicle is equipped with a timing belt.
     
    Note the mileage of the vehicle. The average replacement interval for a timing belt is approximately 60,000 miles (96,000 km).
     

    Interference Engines

    Engines, chain-or belt-driven, can be classified as either free-running or interference, depending on what would happen if the piston-to-valve timing were disrupted. A free-running engine is designed with enough clearance between the pistons and valves to allow the crankshaft to rotate (pistons still moving) while the camshaft stays in one position (several valves fully open). If this condition occurs normally, no internal engine damage will result. In an interference engine, there is not enough clearance between the pistons and valves to allow the crankshaft to turn without the camshaft being in time.

    An interference engine can suffer extensive internal damage if a timing belt fails. The piston design does not allow clearance for the valve to be fully open and the piston to be at the top of its stroke. If the belt fails, the piston will collide with the valve and will bend or break the valve, damage the piston, and/or bend a connecting rod. When this type of failure occurs, the engine will need to be replaced or disassembled for further internal inspection; either choice costing many times that of replacing the timing belt.

    Inspection




    NOTE
    For manufacturers recommended service interval, refer to the maintenance interval chart located in this manual.

    The average replacement interval for a timing belt is approximately 60,000 miles (96,000km). If, however, the timing belt is inspected earlier or more frequently than suggested, and shows signs of wear or defects, the belt should be replaced at that time.


    WARNING
    Never allow antifreeze, oil or solvents to come into with a timing belt. If this occurs immediately wash the solution from the timing belt. Also, never excessive bend or twist the timing belt; this can damage the belt so that its lifetime is severely shortened.



    Click image to see an enlarged view

    Fig. Never bend or twist a timing belt excessively, and do not allow solvents, antifreeze, gasoline, acid or oil to come into contact with the belt

    Inspect both sides of the timing belt. Replace the belt with a new one if any of the following conditions exist:



    Hardening of the rubber-back side is glossy without resilience and leaves no indentation when pressed with a fingernail
     
    Cracks on the rubber backing
     
    Cracks or peeling of the canvas backing
     
    Cracks on rib root
     
    Cracks on belt sides
     
    Missing teeth or chunks of teeth
     
    Abnormal wear of belt sides-the sides are normal if they are sharp, as if cut by a knife
     

    If none of these conditions exist, the belt does not need replacement unless it is at the recommended interval. The belt MUST be replaced at the recommended interval.


    WARNING
    On interference engines, it is very important to replace the timing belt at the recommended intervals, otherwise expensive engine damage will likely result if the belt fails.



    Click image to see an enlarged view

    Fig. Broken tooth may be due to a damaged pulley



    Click image to see an enlarged view

    Fig. Back surface worn or cracked from a possible overheated engine or interference with the belt cover



    Click image to see an enlarged view

    Fig. Side wear from improper installation



    Click image to see an enlarged view

    Fig. Worn teeth from excessive belt tension, camshaft or distributor not turning properly, or fluid leaking on the belt

    Removal & Installation




    NOTE
    The radio may have a coded theft protection circuit. Obtain the code before disconnecting the battery, removing the radio fuse, or removing the radio.


    CAUTION
    Timing belt maintenance is extremely important. All Hyundai models use interference-type non-freewheeling engines. Should the timing belt break in these engines, the valves in the cylinder head will come in contact with the pistons, causing major engine damage. The recommended replacement interval for timing belts is 60,000 miles.


    CAUTION
    On models with an air bag, wait at least 90 seconds from the time that the ignition switch is turned to the LOCK position and the battery is disconnected before performing any further work.

    1MZ-FE Engine
    1. Before servicing the vehicle, refer to the Precautions section.
    2.  
    3. Remove all necessary components for access to the upper timing belt cover. Remove the 8 bolts and lift off the upper (No. 2) cover.
    4.  
    5. Paint matchmarks on the timing belt at all points where it meshes with the pulleys and the lower timing cover.
    6.  
    7. Set the No. 1 cylinder to Top Dead Center (TDC) of the compression stroke and check that the timing marks on the camshaft timing pulleys are aligned with those on the No. 3 timing cover. If not, turn the engine 1 complete revolution (360 degrees) and check again.
    8.  
    9. Remove or disconnect the following:

      Timing belt tensioner and the dust boot
       

    10.  
    11. Turn the right camshaft pulley clockwise slightly to release tension, then remove the timing belt from the pulleys.

      Upper (No. 3) and lower (No. 1) timing belt covers
       
      Timing belt guide
       
      Timing belt from the engine
       

    12.  


    NOTE
    If the timing belt is to be reused, draw a directional arrow on the timing belt in the direction of engine rotation (clockwise) and place matchmarks on the timing belt and crankshaft gear to match the drilled mark on the pulley.



    Click image to see an enlarged view

    Fig. Camshaft and crankshaft pulley positioning for timing belt installation-3.0L (1MZ-FE) engine

    To install:


    NOTE
    If the old timing belt is being reinstalled, be sure the directional arrow is facing in the original direction and that the belt and crankshaft gear matchmarks are properly aligned.

    1. Install the lower (No. 1) timing cover and tighten the bolts.
    2.  
    3. Set the No. 1 cylinder to TDC again. Turn the right camshaft until the knock pin hole is aligned with the timing mark on the No. 3 belt cover. Turn the left pulley until the marks on the pulley are aligned with the mark on the No. 3 timing cover.
    4.  
    5. Check that the mark on the belt matches with the edge of the lower cover. If not, shift it on the crank pulley until it does. Turn the left pulley clockwise a bit and align the mark on the timing belt with the timing mark on the pulley. Slide the belt over the left pulley. Now move the pulley until the marks on it align with the one on the No. 3 cover. There should be tension on the belt between the crankshaft pulley and the left camshaft pulley.
    6.  
    7. Align the installation mark on the timing belt with the mark on the right side camshaft pulley. Hang the belt over the pulley with the flange facing inward. Align the timing marks on the right pulley with the one on the No. 3 cover and slide the pulley onto the end of the camshaft. Move the pulley until the camshaft knock pin hole is aligned with the groove in the pulley, then install the knock pin. Tighten the bolt to 55 ft. lbs. (75 Nm).
    8.  
    9. Position a plate washer between the timing belt tensioner and the block, then press in the pushrod until the holes are aligned between it and the housing. Slide a 0.05 in. Allen wrench through the hole to keep the pushrod set. Install the dust boot, and then install the tensioner. Tighten the bolts to 20 ft. lbs. (26 Nm). Don't forget to pull out the Allen wrench.
    10.  
    11. Turn the crankshaft clockwise 2 complete revolutions and check that all marks are still in alignment. If they aren't, remove the timing belt and start over again.
    12.  
    13. Install the remaining components.
    14.  

    1UZ-FE & 3UZ-FE Engines


    Click image to see an enlarged view

    Fig. Exploded view of the timing belt and cover assembly and related components-4.3L (3UZ-FE) engine shown

    1. Remove all necessary components for access to the right-hand side No. 3 and No. 2, and left-hand side No. 2 timing belt covers, then remove the covers.
    2.  
    3. Turn the crankshaft pulley and align it's groove with the timing mark0
    4.  
    5. Loosen crankshaft pulley bolt, then set the No. 1 cylinder to about 50°ATDC on the compression stroke. With the crankshaft pulley notch aligned with the0
    6.  
    7. Remove or disconnect the following, as applicable for the vehicle:

      Timing belt tensioner. Using the proper tool, loosen the tension between the left side and right side timing pulleys by slightly turning the left side camshaft clockwise.
       
      Timing belt from the camshaft timing pulleys
       
      Power steering pump pulley
       
      Alternator
       
      Drive belt tensioner
       
      Bolt and timing pulleys, using the proper tool
       
      Bolt and the crankshaft pulley with the proper tool.
       
      Fan bracket
       
      Hydraulic pump, on SC 400
       
      Mounting bolts and the No. 1 timing belt cover
       
      2 upper and lower timing belt covers
       
      Timing belt guide (No. 1 crank position sensor plate)
       
      Timing belt
       
      No. 1 and No. 2 timing belt idler pulleys, if necessary.
       

    8.  


    NOTE
    If the timing belt is to be reused, draw a directional arrow on the timing belt in the direction of engine rotation (clockwise) and place matchmarks on the timing belt and crankshaft gear to match the drilled mark on the pulley.



    Click image to see an enlarged view

    Fig. Timing belt sprocket mark alignment for belt installation-Lexus 4.0L (1UZ-FE) engine

    To install:

    1. Align the installation mark on the timing belt with the drilled mark of the crankshaft timing pulley. Install the timing belt on the crankshaft timing pulley, No. 1 idler pulley and the No. 2 idler pulley.
    2.  


    NOTE
    If the old timing belt is being reinstalled, be sure the directional arrow is facing in the original direction and that the belt and crankshaft gear matchmarks are properly aligned.

    1. Install the timing belt guide (No. 1 crank angle sensor plate) with the cup side facing forward. Replace the timing belt cover spacer.
    2.  
    3. Install the No. 1 timing belt cover and tighten the mounting bolts. On the SC400, install the hydraulic pump. Install the fan bracket.
    4.  
    5. Align the pulley set key on the crankshaft with the key groove of the pulley. Install the pulley, using the proper tool to tap in the pulley. Tighten the pulley bolt to 181 ft. lbs. (245 Nm).
    6.  
    7. Align the knock pin on the right side camshaft with the knock pin of the timing pulley. Slide on the timing pulley with the right side mark facing forward. Tighten the bolt to 80 ft. lbs. (108 Nm).
    8.  
    9. Align the knock pin on the left side camshaft with the knock pin of the timing pulley. Slide on the timing pulley with the left side mark facing forward. Tighten the bolt to 80 ft. lbs. (108 Nm).
    10.  
    11. Turn the crankshaft pulley and align its groove with the0
    12.  
    13. Install the timing belt to the left side camshaft timing pulley by:
      1. Using the proper tool, slightly turn the left side timing pulley clockwise. Align the installation mark of the timing belt with the timing mark of the camshaft timing pulley and hang the timing belt on the left side camshaft pulley.
      2.  
      3. Using the proper tool, align the timing marks of the left side camshaft pulley and the timing belt rear plate.
      4.  
      5. Check that the timing belt has tension between crankshaft timing pulley and the left side camshaft pulley.
      6.  

    14.  
    15. Install the timing belt to the right side camshaft timing pulley by:
      1. Using the proper tool, slightly turn the right side timing pulley clockwise. Align the installation mark of the timing belt with the timing mark of the camshaft timing pulley and hang the timing belt on the right side camshaft pulley.
      2.  
      3. Using the proper tool, align the timing marks of the right side camshaft pulley and the timing belt rear plate.
      4.  
      5. Check that the timing belt has tension between the crankshaft timing pulley and the right side camshaft pulley.
      6.  

    16.  
    17. The timing belt tensioner must be set prior to installation. The tensioner can be set as follows:
      1. Place a plate washer between the tensioner and a block. Using a suitable press, press in the pushrod using 220-2205 lbs. (100-1000kg) of pressure.
      2.  
      3. Align the holes of the pushrod and housing, pass the proper tool (0.05 in. Allen wrench) through the holes to keep the setting position of the pushrod.
      4.  
      5. Release the press and install the dust boot on the tensioner.
      6.  

    18.  
    19. Install the tensioner and tighten the bolts to 20 ft. lbs. (26 Nm). Remove the tool from the tensioner.
    20.  
    21. Turn the crankshaft pulley two complete revolutions from TDC-to-TDC. Always turn the crankshaft clockwise. Check that each pulley aligns with the timing marks.
    22.  
    23. Install all remaining components in the reverse order of removal.
    24.  

    1uz-FE Engine
    1. Remove all necessary components for access to the right-hand side No. 3 and No. 2, and left-hand side No. 2 timing belt covers, then remove the covers.
    2.  
    3. Turn the crankshaft pulley and align it's groove with the timing mark 0 of the No. 1 timing cover. Check that the timing marks of the camshaft timing pulleys and timing belt rear plates are aligned. If not, turn the crankshaft 1 full revolution (360 degrees).
    4.  
    5. Remove the timing belt tensioner. Using the proper tool, loosen the tension between the left side and right side timing pulleys by slightly turning the left side camshaft clockwise.
    6.  
    7. Disconnect the timing belt from the camshaft timing pulleys. Using the proper tool, remove the bolt and the timing pulleys.
    8.  
    9. Remove the bolt and the crankshaft pulley with the proper tool. Remove the fan bracket. On the SC400, remove the hydraulic pump.
    10.  
    11. Remove the mounting bolts and the No. 1 timing belt cover.
    12.  
    13. Remove the 2 upper and lower timing belt covers.
    14.  
    15. Remove the timing belt guide (No. 1 crank position sensor plate).
    16.  
    17. Remove the timing belt.
      NOTE
      If the timing belt is to be reused, draw a directional arrow on the timing belt in the direction of engine rotation (clockwise) and place matchmarks on the timing belt and crankshaft gear to match the drilled mark on the pulley.



      Click image to see an enlarged view

      Fig. Timing belt sprocket mark alignment for belt installation-Lexus 4.0L (1UZ-FE) engine

    18.  

    To install:

    1. Align the installation mark on the timing belt with the drilled mark of the crankshaft timing pulley. Install the timing belt on the crankshaft timing pulley, No. 1 idler pulley and the No. 2 idler pulley.
      NOTE
      If the old timing belt is being reinstalled, be sure the directional arrow is facing in the original direction and that the belt and crankshaft gear matchmarks are properly aligned.

    2.  
    3. Install the timing belt guide (No. 1 crank angle sensor plate) with the cup side facing forward. Replace the timing belt cover spacer.
    4.  
    5. Install the No. 1 timing belt cover and tighten the mounting bolts. On the SC400, install the hydraulic pump. Install the fan bracket.
    6.  
    7. Align the pulley set key on the crankshaft with the key groove of the pulley. Install the pulley, using the proper tool to tap in the pulley. Tighten the pulley bolt to 181 ft. lbs. (245 Nm).
    8.  
    9. Align the knock pin on the right side camshaft with the knock pin of the timing pulley. Slide on the timing pulley with the right side mark facing forward. Tighten the bolt to 80 ft. lbs. (108 Nm).
    10.  
    11. Align the knock pin on the left side camshaft with the knock pin of the timing pulley. Slide on the timing pulley with the left side mark facing forward. Tighten the bolt to 80 ft. lbs. (108 Nm).
    12.  
    13. Turn the crankshaft pulley and align its groove with the 0 timing mark on the No. 1 timing belt cover. Using the proper tool, turn the crankshaft timing pulley and align the timing marks of the camshaft timing pulley and the timing belt rear plate.
    14.  
    15. Install the timing belt to the left side camshaft timing pulley by:
      1. Using the proper tool, slightly turn the left side timing pulley clockwise. Align the installation mark of the timing belt with the timing mark of the camshaft timing pulley and hang the timing belt on the left side camshaft pulley.
      2.  
      3. Using the proper tool, align the timing marks of the left side camshaft pulley and the timing belt rear plate.
      4.  
      5. Check that the timing belt has tension between crankshaft timing pulley and the left side camshaft pulley.
      6.  

    16.  
    17. Install the timing belt to the right side camshaft timing pulley by:
      1. Using the proper tool, slightly turn the right side timing pulley clockwise. Align the installation mark of the timing belt with the timing mark of the camshaft timing pulley and hang the timing belt on the right side camshaft pulley.
      2.  
      3. Using the proper tool, align the timing marks of the right side camshaft pulley and the timing belt rear plate.
      4.  
      5. Check that the timing belt has tension between the crankshaft timing pulley and the right side camshaft pulley.
      6.  

    18.  
    19. The timing belt tensioner must be set prior to installation. The tensioner can be set as follows:
      1. Place a plate washer between the tensioner and a block. Using a suitable press, press in the pushrod using 220-2205 lbs. (100-1000kg) of pressure.
      2.  
      3. Align the holes of the pushrod and housing, pass the proper tool (0.05 in. Allen wrench) through the holes to keep the setting position of the pushrod.
      4.  
      5. Release the press and install the dust boot on the tensioner.
      6.  

    20.  
    21. Install the tensioner and tighten the bolts to 20 ft. lbs. (26 Nm). Remove the tool from the tensioner.
    22.  
    23. Turn the crankshaft pulley two complete revolutions from TDC-to-TDC. Always turn the crankshaft clockwise. Check that each pulley aligns with the timing marks.
    24.  
    25. Install all remaining components in the reverse order of removal.
    26.  

     
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