BMW Cars 1999-06

Valve Lash (Clearance) Adjustment

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All engines are equipped with hydraulic valve lash adjusters. No adjustments are possible.

Most of the BMW models covered in this manual have hydraulically adjusted valves, except for the E30 series M3 S14 and 325 M20 engines. Valve lash on these engines should be checked and adjusted as necessary during the BMW Inspection I maintenance, which is approximately every 15,000 miles (24,000 km) as determined by the Service Interval lights. It is important to check and adjust the lash to make up for wear in the valve train. Excessive valve clearance could cause noisy valve operation and reduced power. Insufficient clearance in the valve train could cause the valves to be overheated, as the valves dissipate heat from the head of the valve as it is closed and rests on the valve seat. An overheated valve can distort, crack, break or cause the valve to burn and reduce compression. The M20 BMW engine features a unique adjuster design that makes it easy to hold the required dimension while tightening the locknut; thus, valve adjustment is relatively easy.

The S14 engines require the use of BMW tool No. 11 3 170, or its equivalent, to depress the valve tappet, compressed air to displace the valve shim, and a selection of adjustment shims. The shims are available in increments of 0.002 inches (0.05mm) and range in thickness from 0.118-0.167 inches (3.00-4.25mm).

The camshaft is driven at an exact two to one ratio of the crankshaft. For every two revolutions the crankshaft completes, the camshaft rotates once.

The camshaft has lobes that are used to open the valves in the proper sequence to allow a charge of fuel and air to enter the combustion chamber via the intake valve and to dispense the burnt gasses via the exhaust valve. The lobe has a pointed end called the toe, and a smooth rounded end referred to as the heel. The portion of the camshaft lobe between the heel and the toe is called the ramp. The opening ramp presses on the rocker or tappet shim to open the valve, and the closing ramp guides the valve closed.

A camshaft is considered to be in the "at rock" or overlap position when the camshaft's exhaust lobe is guiding the exhaust valve closed and the intake lobe is beginning to open the intake valve for a given cylinder.

The valves for a cylinder are adjusted when the heel of the intake and exhaust camshaft lobes are both equally facing their rocker or valve adjustment shim for that cylinder.

The valves on BMW models should be checked and adjusted when the engine is cold.

All engines are equipped with hydraulic valve lash adjusters. No adjustments are possible.

All engines are equipped with hydraulic valve lash adjusters. This design does not require adjustments nor are adjustments possible.

All engines are equipped with hydraulic valve lash adjusters. No adjustments are possible.

M20 Engine





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Fig. Checking the valve lash between the valve and the rocker arm adjusting eccentric-M20 engine shown



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Fig. Valve lash adjusting sequence

  1. Make sure the engine is cold.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the valve cover, making sure to note the location of the cap nuts and bolts for proper reassembly. If necessary, remove the air cleaner and/or main air intake hose, then label and disconnect the attached hoses/vacuum lines as needed.
  6.  


NOTE
To ease rotation of the engine, it may be helpful to remove the spark plugs as outlined in this section.

  1. It will be necessary to properly position the camshaft by turning the engine to Top Dead Center (TDC) for each cylinder. To do this, the engine is rotated in a clockwise direction using a suitable socket, ratchet and if necessary, an extension to turn the crankshaft via the crankshaft pulley bolt.
  2.  
  3. The engine must be rotated to Top Dead Center (TDC) on the firing stroke for each cylinder to properly position the camshaft for the valves to be adjusted. A cylinder is at Top Dead Center (TDC) on the firing stroke when the piston for that cylinder is at its topmost position in the cylinder bore and:

    The ignition rotor is pointing toward the terminal of the distributor cap for that cylinder's ignition wire
     
    The heel of both the intake and exhaust camshaft lobes are facing their rockers for the particular cylinder
     
    The camshaft of an opposing cylinder is in the overlap position as outlined in the valve lash adjusting sequence chart
     

  4.  

The valve adjustment clearance specifications are as follows:



Cold: 0.010 inches (0.25mm)
 
Warm: 0.012 inches (0.30mm)
 

  1. Check the clearance between the intake valve rocker eccentric adjuster and the intake valve using correct sized feeler gauge. The feeler gauge should pass the rocker eccentric adjuster with a slight resistance. If in doubt about the clearance, recheck the clearance using a feeler gauge that is 0.001 inch (0.02mm) larger and smaller. The smaller feeler gauge should slide through easily and the larger feeler gauge should not be able to fit between the rocker and the valve.
  2.  
  3. If the clearance is not correct, insert a bent wire tool (made with a piece of coat hanger) or use a suitable hex key inserted into the small hole in the rocker's adjusting eccentric, located in the outer end of the rocker arm. Using a 10mm wrench to loosen the adjustment locknut, slightly loosen the nut and rotate the adjustment eccentric with the wire as the gauge is slid between the adjustment eccentric and the valve. When the gauge just fits between the valve and adjustment eccentric and can be slid back and forth with just a slight resistance, hold the eccentric with the adjusting wire or hex key and then tighten the locknut.
  4.  
  5. Recheck the clearance to make sure it has not changed while tightening the lock nut.
  6.  
  7. Then check and adjust as necessary the valve clearance for the exhaust valve-to-exhaust rocker.
  8.  
  9. Follow the engine's firing order, rotate the crankshaft clockwise until the next cylinder in the engine's firing order is at TDC. The firing order for the M20 engine is: 1-5-3-6-2-4 .
  10.  
  11. Repeat the adjustment procedures for each cylinder's intake and exhaust valves.
  12.  
  13. Reinstall the valve cover using a new gasket. Tighten the cover cap nuts or bolts evenly, starting at the center and working outward. a very little at a time, alternately criss-crossing in order to bring the cam cover down onto the gasket evenly in all areas. Be careful not to overtighten the cover cap nuts/bolts. Torque to 72-84 inch lbs. (8-10 Nm).
  14.  
  15. Reconnect all disconnected hoses and, if necessary, replace the air cleaner.
  16.  

S14 Engines



The S14 engine requires the use of BMW tool No. 11 3 170 or its equivalent to compress the valve tappet, compressed air to displace the shim, and a selection of adjustment shims. A micrometer may be needed to determine shim thickness if the markings on the adjustment shim have worn off.



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Fig. Turn the valve buckets so the notches are facing outward before checking the adjustment-S14 engine



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Fig. Shown from top to bottom are the valve adjustment shim, tappet, valve keeper, retainer, valve seal, inner/outer spring, spring seat and valve for S14 engines



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Fig. Check the valve adjustment between the heels of the camshaft lobes and the adjustment shim, when the camshafts are in this position-S14 engines

  1. Make sure the engine is cold.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the valve cover.
  6.  


NOTE
To ease rotation of the engine, it may be helpful to remove the spark plugs as outlined in this section.

  1. Rotate the engine's crankshaft in a clockwise direction using a suitable socket, ratchet and if necessary, an extension to turn the crankshaft via the front pulley bolt to properly position the camshaft to Top Dead Center (TDC) on the firing stroke for each cylinder. A cylinder is at Top Dead Center (TDC) on the firing stroke when the piston for that cylinder is at its topmost position in the cylinder bore and:

    The ignition rotor is pointing toward the terminal of the distributor cap for that cylinder's ignition wire
     
    The heel of both the intake and exhaust camshaft lobes are facing their tappet adjustment shims for the particular cylinder
     
    The camshaft of an opposing cylinder is in the overlap position as outlined in the valve lash adjusting sequence chart
     

  2.  
  3. Turn the engine until the toe of the No. 1 cylinder exhaust and intake valve camshaft lobes are both pointing straight up.
  4.  

The valve adjustment clearance specifications are as follows:



Cold: 0.010-0.014 inches (0.26-0.35mm)
 
Warm: 0.012-0.016 inches (0.31-0.40mm)
 

  1. Measure the valve clearance for the cylinder when the cylinder is at Top Dead Center (TDC) on the firing stroke. The camshaft lobe's heel should be facing the adjustment shim as shown in the illustration. Make sure the toe (maximum lift area of the camshaft lobe) is opposite to the adjustment shim before each measurement.
  2.  
  3. If the measured valve clearance is not within the valve clearance specification range, the valve adjustment shim must be replaced. If the clearance is less than the minimum clearance specification, a smaller (thinner) shim must be used. If the measured clearance exceeds the maximum clearance specification a larger (thicker) shim must be installed.
  4.  
  5. To replace a valve shim, proceed as follows:
    1. Move the tappets so the slotted edges are facing outward.
    2.  

  6.  


NOTE
When using BMW Tool No. 11 3 170 or its equivalent, side E of the tool is used to compress the intake valve tappet, and side A of the tool is used to compress the exhaust valve tappet.

  1. Use BMW Tool No. 11 3 170 or its equivalent to compress the valve tappet.
  2.  
  3. Using compressed air aimed toward the slot in the tappet, displace the shim.
  4.  


NOTE
A micrometer may be needed to determine shim thickness if the markings on the shim have been worn away.

  1. Determine the correct shim size needed by comparing the measured valve clearance to the valve clearance specification.
    1. If the measured clearance is LESS than the smallest dimension of the valve clearance specification range, a smaller (thinner) shim is needed. To determine the correct shim size:

      Subtract the actual measured clearance from the maximum allowable clearance. This will determine the amount of additional clearance required, hence a smaller (thinner) adjustment shim will be required. Subtract the amount of the additional clearance required from the size of the existing shim to determine the size of the shim to be installed.
       

    2.  
    3. If the measured clearance is GREATER than the largest dimension of the valve clearance specification range, a larger (thicker) shim is needed. To determine the correct shim size:

      Subtract the maximum allowable clearance from the actual measured clearance. This will determine the amount the clearance must be decreased, hence a larger (thicker) adjustment shim will be required. Add the amount the clearance must be decreased to the size of the existing adjustment shim to determine the size of the adjustment shim to be installed.
       

    4.  

  2.  


NOTE
Because adjustment shims are only available in increments of 0.002 in. (0.05mm) it may be necessary to substitute the next size larger (thicker) or smaller (thinner) adjustment shim to obtain a clearance that is within the range of the valve clearance specifications provided.

  1. Apply a thin layer of oil to the adjustment shim to be installed and slide it between the camshaft lobe and the edges of the tappet.
  2.  
  3. Make sure the adjustment shim is fully seated in the tappet.
  4.  
  5. Remove the tool and recheck the clearance.
  6.  

  1. Rotate the engine clockwise. Repeat the previous valve checking/adjustment procedures for the intake and exhaust valves using the S14 engine firing order which is: 1-3-4-2 .
  2.  
  3. When all the clearances are within the specified range, reinstall the cam cover, reinstall the battery ground cable, start the engine, and check for leaks and normal operation.
  4.  

 
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