BMW Coupes and Sedans 1970-1988 Repair Guide

Timing Chain and Tensioner

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REMOVAL & INSTALLATION



Except M3, M5 and M6 Models
  1. Rotate the crankshaft to set the No. 1 piston at TDC, at the beginning of its compression stroke.
  2.  
  3. Remove the distributor (6-cylinder engines only).
  4.  
  5. Remove the cylinder head cover, air injection pipe and guard plate.
  6.  
  7. Drain the cooling system and remove the thermostat housing.
  8.  


CAUTION
When draining coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze, and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Remove the upper timing housing cover.
  2.  
  3. Remove the timing chain tensioner piston by unscrewing the cap cautiously.
  4.  

The piston is under heavy spring tension.

  1. Remove the drive belts and fan.
  2.  
  3. Remove the flywheel guard and lock the flywheel with a locking tool.
  4.  
  5. Remove the vibration damper assembly.
  6.  

The crankshaft Woodruff key should be in the 12 o'clock position.

  1. Remove upper and lower timing covers as described above.
  2.  
  3. Turn the crankshaft so that the No. 1 cylinder is at firing position. Open the camshaft lockplates if so equipped, remove the bolts and remove the camshaft sprocket.
  4.  
  5. On 4-cylinder engines:
    1. Remove the bottom circlip holding the chain guide rail to the block. Loosen the upper pivot pin until the guide rail rests against the forward part of the cylinder head gasket.
    2.  
    3. Remove the timing chain from the sprockets and remove the guide rail by pulling downward and swinging the rail to the right.
    4.  
    5. Remove the chain from the guide rail and remove it from the engine.
    6.  
    7. On the 4-cylinder engine, take the timing chain off top and bottom sprockets and remove carefully from the guide rail.
    8.  

  6.  
  7. On 6-cylinder engines:
    1. Remove the chain from the lower sprocket, swing the chain to the right front and out of the guide rail and remove the chain from the engine.
    2.  

  8.  
  9. Installation is the reverse of removal, but note the following:
  10.  
  11. Be sure that No. 1 piston remains at the top of its firing stroke and the key on the crankshaft is in the 12 o'clock position.
  12.  
  13. On 4-cylinder engines:
    1. Position the camshaft flange so that the dowel pin bore is located at the 6 o'clock position and the notch in the top of the flange aligns with the cast tab on the cylinder head.
    2.  
    3. Position the chain in the chain guide rail and move the rail upward and to the left, engaging the lower locating pivot pin and threading the upper pivot pin into the block. Install the circlip on the lower guide pin. On the 318i, simply locate the chain carefully in the guide rail.
    4.  
    5. Engage the chain on the crankshaft sprocket and fit the camshaft sprocket into the chain.
    6.  
    7. Align the gear dowel pin to the camshaft flange and bolt the sprocket into place. Use new lockplates (where so equipped), and secure the bolt heads.
    8.  

  14.  
  15. On 6-cylinder engines:
    1. Position the camshaft flange so that the dowel pin bore is between the 7 and 8 o'clock position and the upper flange bolt hole is aligned with the cast tab on the cylinder head.
    2.  
    3. Position the chain on the guide rail and swing the chain inward and to the left.
    4.  
    5. Engage the chain on the crankshaft gear and install the camshaft sprocket into the chain.
    6.  
    7. Align the gear dowel pin to the camshaft flange and bolt and sprocket into place. Tighten the sprocket bolts to 6.5-7.5 (8-10 Nm).
    8.  

  16.  
  17. Install the chain tensioner piston, spring and cap plug, but do not tighten.
  18.  
  19. To bleed the chain tensioner, fill the oil pocket, located on the upper timing housing cover, with engine oil and move the tensioner back and forth with a screwdriver until oil is expelled at the cap plug. Tighten the cap plug securely.
  20.  
  21. Complete the assembly in the reverse order of removal. Check the ignition timing and the idle speed. Be sure the flywheel holder is removed before any attempt is made to start the engine.
  22.  

M3 Model
  1. Remove the timing case cover.
  2.  
  3. Refer to the camshaft removal procedure below. Follow the procedure to the point where the 2 camshaft drive sprockets are unbolted and remove them. It is not necessary to remove the cover from the rear of the head.
  4.  
  5. Make sure to catch the washer and lockwashers which will be released at the front as the rest of this step is performed. Now, remove the 2 mounting bolts for the guide rail, which is located on the left (driver's) side of the engine. These are accessible from the rear.
  6.  
  7. Pull the guide rail forward and then turn it clockwise on its axis, looking at it from above, to free it from the chain.
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  9. Note the relationships between timing chain and sprocket marks. Remove the chain by separating it from the sprockets at top and bottom.
  10.  
  11. Engage the timing chain with the crankshaft sprocket so marks line up. Route the chain up through where the guide rail will go. Install the guide rail in reverse of the removal procedure.
  12.  
  13. Then engage the chain with the driver's side ("E") sprocket with the marks lined up. Bolt this sprocket and the lockplate onto the front end of the intake camshaft. Use the adapter to keep the sprocket from turning, and tighten the bolts to 6-7 ft. lbs. (8-9 Nm). Turn this camshaft in the direction opposite to normal rotation to tension the timing chain on that side.
  14.  
  15. Now, engage the timing marks with the mark on the passenger's side ("A") sprocket and then install the sprocket and lockplate onto the front end of the exhaust camshaft. Again, use the adapter to keep the sprocket from turning, and tighten the bolts to 6-7 ft. lbs. (8-9 Nm). Make sure the timing chain has stayed in time.
  16.  
  17. Slide the chain tensioner piston into its cylinder. Install a new seal. Now install the spring with the conical end out. Install the cap which retains the spring and tighten it to 29 ft. lbs. (38 Nm).
  18.  
  19. Turn the engine one revolution in the normal direction of rotation. Recheck the timing. With the crankshaft at TDC, one groove on each camshaft faces inward and another on each faces the cast boss on the nearby bearing cap.
  20.  
  21. Perform the remaining procedures for camshaft installation, including installing and centering the top chain guide rail and centering it.
  22.  
  23. Install the timing case cover as described above.
  24.  

M5 and M6 Models
  1. Remove the fan shroud and the fan. Remove the cylinder head cover. Remove the timing cover as described above.
  2.  
  3. Refer to the camshaft removal procedure below. Follow the procedure to the point where the 2 camshaft drive sprockets are unbolted and remove them. It is not necessary to perform Step 4 to remove the cover from the rear of the head.
  4.  
  5. Refer to the appropriate procedure and remove the water pump.
  6.  
  7. Remove the 2 mounting bolts for the guide rail, which is located on the left (driver's) side of the engine. These are accessible from the rear. Turn the guide rail counterclockwise on its axis, looking at it from above to clear the chain and block and remove it. Be careful to retain all washers.
  8.  
  9. Note the relationships between timing chain and sprocket marks. Remove the timing chain.
  10.  

To install:
  1. Install the timing chain with the marks on all 3 sprockets aligned with marked links on the chain. Make sure the chain runs on the inside of the guide sprocket on the left side of the engine and along the groove in the lower tensioning rail. Install the chain onto the camshaft drive sprockets and then install the sprockets onto the camshafts (note that the exhaust side sprocket is marked A and the intake sprocket is marked E. Then, install the guide rail with all washers and lockwashers by rotating it into position in reverse of the removal procedure.
  2.  
  3. Tighten the camshaft drive sprockets, install the chain tensioner, and install the upper guide rail as described in the camshaft removal and installation procedure. Reverse the remaining removal steps to complete the procedure. Make sure to refill the cooling system with an appropriate antifreeze/water mix and to bleed the cooling system.
  4.  

 
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