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M30 Valve Adjustment

Adjusting the valves on your m30 engine is a mandatory part of proper maintenance.  It is an important compnonent of proper tune, maintains the health of your camshaft and valve train components, and is an excellent time to inspect other significant engine components. 
The first step is disassembly.  I always start by removing the airbox, air flow meter, intake boot, and breather/idle control hoses.
 
 
Next, I carefully remove the spark plug wires and then the plugs themselves.  Then, you will need to remove the support arms that connect the valve cover to the intake manifold.  You are left with a bare valve cover that is ready to remove. 
 
 
Once you have everything safely cleared out of the way, you can lift off the valve cover.  Always take care not to introduce dirt and debris into the cylinder head and valve train.  You should be looking at something like this:
 
 
Once my valve cover is off, my first step is always checking the tightness of the oil spray bar banjo bolts.  They are known to back out over time.  In the old days, people would drill a hole in the head of the bolt and use steel wire to secure them.  BMW now has a new bolt available that comes with a loctite type product pre-applied.  You can always apply your own loctite to your bolts after cleaning them.  Make sure your aluminum crush washer are in good shape.  Don't reuse them if they are at all questionable.  They are cheap.  These bolts should be torqued to 8-10 ft/lbs.  Do not overtighten!
 
In order to adjust your valve clearance, the lobe of the cam of the corresponding valve you wish to adjust must be pointing straight down at the surface of the block.  It is important not to have it pointing at the ground, which is a common misconception.  You will have to rotate the engine at this point.  This is why we removed the spark plugs, it makes the engine much easier to rotate.  There are different ways to rotate the engine.  Some people bump the starter, some people will use the alternator pulley, and some people will use the crank hub bolt.  I choose to use a 32mm socket on a 3/4 inch drive socket and rotate the crankshaft.  This method will allow you the ability to make small corrections to the cam placement for proper adjustment.  Once you have the lobe of the cam where you want it, go ahead and use your 10mm wrench to loosen the eccentric bolt.  Loosenening is pushing away from you (towards driver side) on the intake valves and pulling towards you (passenger side) on the exhaust valves.  You should excersise care when loosening because if the bolt is too tight you can compress the valve spring and push into the combustion chamber.  In these cases, I tend to "rock" the wrench in order to apply more of an impact wrench style force rather than a steady even force. 
 
Adjusting your valve clearance is done by rotating the eccentric on the valve side of the rocker arm.  You will see that the round eccentric has a hole in it.  This hole is used to rotate the eccentric.  Rotating the eccentric back and forth opens and closes the gap between the valve stem and the eccentri itself.  This is due to the eccentric itself being cammed. 
 
The spec for the gap between the eccentric and the valve stem on a stone cold engine is .012 inches.  This is a job that should be done when the car has sat overnight.  Failing to follow that rule will result in an improper adjustment for numerous reasons.  If your m30 has higher mileage or may have been neglected in the past (long valve adjustment intervals) than I find it useful to adjust the valves while measuring the clearance between the rocker foot and the cam's base circle.  The proper spec for this is .009 inches between the rocker pad and the base circle of the cam.  Many sets of feeler gauges will not come with a .009.  In this case you use what can be referred to as "go, no-go" with a .008 and a .010 feeler gauge.  In other words, a .008 should slide right in and a .010 will not slide in at all.  This will effectively give you .009 between the rocker pad and the cam lobe base circle.
 
Adjusting will be cumbersome at first, byt you will soon get the hang of it.  It is a blend of adjusting the clearance, checking the clearance with your feeler gauges, and then tightening the eccentric bolt when it is just right.  Here is my set-up:
 
 
I use a slim 10mm wrench, a small allen wrench to rotate the eccentric, and my feeler gauges.  I chose to purchase the pre-bent feeler gauges.  I remove them from the stack and use them individually.  Take your time and double check your work.  I keep a little note and check off each valve I adjust.  This allows me to make sure I don't miss anything.  Once you have adjusted all 12 and have double checked your adjustments, inspect all around the cylinder head and make sure you have not dropped or knocked anything in.  OBviously, you don't want dirt, debris, or a tool left behind. 
 
Take your time reassembling the engine.  This is a good time to inspect your intake boot and associated hoses.  Cracked, hard, and brittle lines should be replaced.  Make sure to remember all of your connections and take care to properly re-install your plugs and plug wires.  Once you have everything back together, start it up.  You should hear a smooth valve train.  Ticking is okay!  These engines are very "mechanical."  They will never be as quiet as a modern hydraulic lifter engine such as the M5x.  You want to hear the sound many describe as a "sewing machine."  If you hear any out of place clicking or tapping, take a long screw driver or a piece of hose and put it up to your ear.  Place the other end on different areas of the valve cover and try and locate the origin of the sound.  Remember to keep in mind that the m30 has very loud injectors.  Use the same screwdriver or piece of hose and listen to an injector while the engine is running.  They should be very crisply opening and closing with a nice tick.  Doing this will help you isolate the injector sounds from the valve train. 
 
All in all, adjusting your valves is a simple process.  It is important not to rush.  Take your time and double check your adjustments.  Remember that some noise from the valve train is normal and your m30 will never be "quiet."  Do not overtighten your valve clearances seeking a quieter engine.  This can result in a poor idle, reduced efficiency, and/or burned exhaust valves. 
 
Note:  The part number for the newer style bajo bolt is:   11 42 1 738 621  There are two of these on your m30.
            The part number for the aluminum crush washers is:  11 42 1 252 343  There are four of these on your m30 (two per banjo bolt).
 
Hopefully, this will be helpful.  If you have any questions or concerns feel free to email me at pldlnr@gmail.com