84 635 Euro valve adjustment

[Rleog]

How frequently is it necessary to adjust valves?

The recent European Car mag has a section on the 6 series; they recommend approx 20,000 miles. Additionally, they recommend checking the bolt tension on the (I forget the term) rail that oils the camshaft. Seems that it could work loose and cause the cam to wear prematurely.

One mechanic I spoke with told me the valves don't need to be adjusted on this car!

[KC Ron Carter]

Banjo Bolts and Valve Adjustment


In the head, on top of the cam, there is an oil sprayer bar that directs oil to lubricate the cam and rockers. The oil spray bar bolts are hollow bolts through which oil passes through, into the oil sprayer bar. Now, these bolts tend to come loose in time from vibration. This can happen in as little as 20k miles, or as long as 150k miles, there is really no "set" mileage that this happens.

BMW has issued a new bolt to fix this problem. Really, what it is is the same bolt with a tad of locktite on the threads. But it is a new partnumber and the old bolt (with no blue locktite) and the new bolt are differentiated by a round circle engraved in the head of the new bolt. The part number for these bolts is 11 42 1 738 621.

Any good (i.e. knowledgable) BMW mechanic should know about this problem on M30s. And whenever you get a valve adjustment (which should be every 15k miles or 1-2 years), the mechanic should check the torque on those bolts. So long as you do that, you should have no problem. Even with the "old" bolts.

BTW, a valve adjustment on these cars should run around $100, give or take. This includes a new valve cover gasket. That is the only repair that I'd take, and have taken, my car to a mechanic to. You really need to get a "feel" to adjust the valves on M30s. It's an art in itself. But if you do do it yourself, you have to do with the engine stone COLD, because otherwise you won't do a good job. (Leave it sitting overnight). Oh, and you will also need a method to turn the engine (remote starter, big socket and wrench to turn crankshaft rotating nut, etc).

Problems with the '86-88 big six engine idle is related to exceeding (vastly) the EPA emissions standards. The things run VERY lean at idle (CO is almost unmeasureable at the tailpipe). None of them idle great - but the above can make it tolerable - and not embarrassing at a stop light (car rocking and rolling). The biggest change is made by opening up the valve adjustment, followed by the correct plugs and a wide gap. You'll notice as these open up with normal wear, the car runs better and better - I'm often disappointed after I tune BOHICA up, 'cause it runs WORSE - and end up resetting the new plugs to the gap the ones that came out were at - and doing the valves again. I'm currently running the valves at 0.014 +.001 - .000 - this seems to work well, and with BOHICA gonna reach 100,000 miles TOMORROW - the cam and lifters look JUST LIKE NEW - the car uses no oil, and the compression is excellent, and very even. It won't hurt the engine to run these wider - and will greatly improve the idle.

http://normgrills.net/bcg/Engine_Mgmt.html#anchor41563757

[Rleog]

Many thank, Ron. I'm more than a little embarrased to be finding out about this now.

I appreciate the time you took to answer.