BMW 318/325/M3/525/535/M5 1989-1993 Repair Information

Except S14 and S38 Engines


See Figures 1 and 2

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Fig. Fig. 1: Checking the valve lash between the valve stem and the rocker arm adjusting eccentric-M20 and M30 engines

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Fig. Fig. 2: Valve lash adjusting sequence

  1. Make sure the engine is as cold as possible. It need not actually sit overnight, but must be cool to the touch-under 95°F (35°C). Several hours should be allowed for cooling if the engine started out at operating temperature.
  3. Remove the valve cover. This will require, in some cases, removal of the air cleaner or main air intake hose, and disconnecting the PCV line or other vacuum lines. Note that the valve cover is secured to the cylinder head by cap nuts, while bolts attach it to the timing cover on the front of the engine. Make sure you remove all the fasteners. Then, lift the cover straight out.
  5. The engine must be rotated to a position that will ensure that there will be no closing effect from the camshaft when the valves are adjusted. This requests a different position for the adjustment of each cylinder. The figure lists the cylinder to be adjusted in the first (left hand) column, and the cylinder whose valves must be watched while positioning the engine in the right hand column. Cylinders are numbered from front to rear, 1 through 4 or 1 through 6. The engine may be rotated by rolling the car in third gear (if it is equipped with a manual transmission) or by installing a socket wrench on the bolt which attaches the front pulley and rotating with the wrench. The valve of the cylinder to be adjusted (left hand column) will be in the fully closed position, compression TDC, so that you can wiggle the rockers up and down slightly, feeling the clearance in the valve train, when the engine is in the proper position. The valve in the cylinder to be watched while rotating the engine (right hand column) must be in the overlap position. At this position, both valves will be slightly open. For example, to position the engine for adjustment of the valves on No. 1 cylinder, watch cylinder No. 4 on 4-cylinder engines, and cylinder No. 6 on 6-cylinder engines. As you rotate the engine in the direction of normal rotation, you'll note a point at which the valve on the right side of the engine (the exhaust valve) begins closing (moving upward). If you crank very slowly, you'll note that, just before the exhaust valve has closed, the intake begins opening. You want to stop rotating the engine when the valves are both open about the same amount. Now, you are ready to adjust cylinder No. 1, as described in the next 2 steps.
  7. Check the clearances on one of the valves with a feeler gauge. The gauge should pass through between the valve and the outer end of the rocker with a slight resistance (don't check between the camshaft and rocker, at the center of the engine). If there is any doubt about the clearance, check with the gauges equivalent, thicker and thinner by 0.002 in. If the specification is, for example, 0.12 in., and the 0.012 in. gauge passes through snugly, and the 0.014 gauge feels tight while a 0.010 gauge slips through easily, the valve is adjusted correctly. If the clearance is not right, insert the bent wire tool (these may be purchased at an automotive supply store or you can make one yourself with a piece of coat hanger) into the small hole in the adjusting cam, which is located in the outer end of the rocker arm. Then, use a 10mm wrench to loosen the adjusting locknut, also located on the end of the rocker. Rotate the adjusting cam with the wire as you slide the gauge between the cam and valve. When the gauge will go in between the valve and adjusting cam and can be slid back and forth with just a slight resistance, hold the position of the cam with the adjusting wire and then tighten the locknut.
  9. Recheck the clearance to make sure it has not changed-if the minimum and maximum dimension gauges behave as described in the step above, the adjustment is correct.
  11. Repeat the adjustment for the other valve on cylinder No. 1, located directly across from the one already adjuster.
  13. Rotate the engine to the next cylinder listed in the left hand column of the figure, watching the valve of the cylinder listed in the right hand column. When the engine is positioned for this cylinder, adjust the valves for it as described in Steps 4, 5 and 6. Then, proceed with the next cylinder in the left hand column in the same way, until all 4- or 6-cylinders have had their valves adjuster.
  15. Replace the valve cover using a new gasket. Tighten the cover cap nuts or bolts a very little at a time and alternately 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 6-7 ft. lbs. (8-10 Nm).
  17. Reconnect all disconnected hoses and, if necessary, replace the air cleaner.