Except M3, M5 and M6 Models
See Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12
All BMW gasoline engines except for the 1987-88 M series, dual overhead camshaft designs are equipped with an overhead camshaft which operate the intake and exhaust valves through rocker arm linkage.
Valve lash on these engines should be adjusted at 8,000-12,500 mile (13,000-20,000 km) intervals, depending on the year of the car. See the owner's manual for exact intervals. It is important to adjust the lash to make up for wear in the valve train, which will cause noisy valve operation and reduced power, or, in some cases, excessive tightness in the valve train, which can cause the valves to burn and may even reduce compression. The BMW engine features a unique adjuster design that makes it easy to hold the required dimension while tightening the locknut; thus, valve adjustment is unusually easy.
- 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) is the minimum. Several hours should be allowed for cooling if the engine was recently at operating temperature.
- Remove the valve cover. This may require the removal of the air cleaner or main air intake hose.
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 off.
- Disconnect the Positive Crankcase Ventilation (PCV) line or other vacuum lines. If unfastening multiple vacuum lines is needed, tag each line prior to removal.
- The engine crankshaft 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 accompanying chart 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 the ring with the wrench. The valve of the cylinder to be adjusted (left hand column) will be in the fully closed position, so that you can wiggle the rockers up and down slightly. 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.
- Check the clearances on one of the valves with a feeler gauge that falls within the limits given in the Tune-Up Specifications chart. For example, if the dimension is 0.010-0.011 inches (0.25-0.30mm), use a 0.28mm gauge. The gauge should pass through between the valve and the outer end of the rocker with slight resistance (don't check between the camshaft and rocker, at the center of the engine). If there is any doubt about the clearance, try both the minimum and maximum specifications. For example, the specification is 0.010-0.011 inches (0.25-0.30mm), and the 0.25mm gauge passes through, but the 0.30mm gauge will not, the valve meets specification and will not need adjustment.
- If the clearance is not correct, insert the bent wire tool supplied with the car (these may also 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 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 tighten the locknut.
- Recheck the clearance to make sure it has not changed.
- Repeat the adjustment for the other valve on cylinder No. 1, located directly across from the one you've already adjusted.
- Then, rotate the engine to the next cylinder listed in the left hand column of the appropriate chart above, 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. 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 adjusted.
- Replace the valve cover using a new gasket. Tighten the cover cap nuts or bolts in small increments 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.
- Fasten all disconnected hoses and, if necessary, replace the air cleaner.
- Start the engine.
See Figure 13
To perform this procedure, a special tool is needed to depress the valves against spring pressure to gain access to the valve adjusting discs. Use BMW Tool 11 3 170 or equivalent. Also needed are: compressed air to lift valve adjusting discs that must be removed and replaced out of the valve tappet; an assortment of adjusting discs of various thicknesses and a precise outside micrometer.
- Make sure the engine is overnight cold. Remove the rocker cover.
- Turn the engine until the No. 1 cylinder intake valve cams are both straight up. The intake cam is labeled A on the cylinder head.
- Slide a flat feeler gauge in between each of the cams and the adjacent valve tappet. Check to see if the clearance is within the specified range. If not, switch gauges and measure the actual clearance. When actual clearance is achieved, proceed to the next step.
- Turn the valve tappets so the grooves machined into the edges are aligned. Looking at the valves from the center of the engine, the right hand tappet's groove should be at about the 5 o'clock position and the left hand tappet's groove should be at about the 7 o'clock position. Use the special tool with the end mark corresponding to the proper valve. In this case use the A end of the tool for the valve marked A. Use the E end of the tool for the E valve. (A is intake, E is exhaust). Slide the proper end of the tool, going from the center of the engine outward, under the cam, with the heel of the tool pivoting on the inner side of the camshaft valley. Force the handle downward until the handle rests on the protrusion on the center of the cylinder head.
- Use compressed air to pop the disc out of the tappet. Read the thickness dimension on the disc.
Determine the thickness required as follows:
- If the valve clearance is too tight, try the next thinner diameter.
- If the valve clearance is too loose, try the next thicker disc.
- Slip the thinner or thicker disc into the tappet with the letter facing downward.
- Rock the valve spring depressing tool out and remove it.
- Recheck the clearance. Change the disc again, if necessary, until the clearance falls within the specified range.
- Turn the engine in firing order sequence (1-5-3-6-2-4 for the 6-cylinder engines or, for the M3 1-3-4-2), turning the crankshaft forward 1 / 3 of a turn each time to get the intake cams to the upward position for each cylinder. Measure the valve clearance and, if it is outside the specified range, follow the steps outlined earlier for all the intake valves.
- Follow the same sequence for all the exhaust valves, going through the firing order.
It is necessary to use the opposite end of the special tool, the end marked E to depress the exhaust valves.
- When all the clearances are in the specified range, replace the cam cover, start the engine, and check for leaks.
See Figure 14
- Remove the rocker cover.
- Rotate the engine (using a socket on the crankshaft pulley nut) until the No. 1 cylinder is at TDC on the firing stroke. Line up the timing marks and also ensure that both No. 1 cylinder valves are loose; if they are not, turn the engine 360°.
- Use the 12mm backup wrench on the nut, then, loosen the locknut. Slide a flat feeler gauge of the proper size (0.30mm) into the gap. If it is necessary to change the clearance, rotate the eccentric, making sure the clearance is always taken up by turning the eccentric toward the operator or away from the centerline of the engine.
- Tighten the nut, and recheck the clearance. Readjusting it if necessary.
- Repeat this step for the other valve on No. 1 cylinder.
- Repeat the step above for each cylinder. Turn the engine 1 / 3 turn forward and adjust each cylinder in the firing order of 1-5-3-6-2-4.
- Replace the valve rocker cover.