Re: E28 valve noise

[Chris Apostol <caposto@xxxxxxx>]

Very timely subject for me.  While doing a compression check on my '86 535i, I happened to look down the front timing chain
cover.  I found three fairly large pieces of what the parts CD calls the "Slide Rail".  They are this plastic type material that
apparently fit around the chain itself.  I found the pieces on the chain tensioner side of the chain.  Not Good.  On the other
side of the chain, I could see the rest of the slide rail in place but it was just resting on the chain.  I could move it easily
with a long screwdriver but it wouldn't come out.  That can't be right.  The chain also seems loose.  The side opposite the chain
tensioner sort of sags.  I would think it should be fairly taught.

Theory:  My chain tensioner went bad and the chain got loose and broke part of the slide rail into pieces.  This could explain the
sporadic hesitation I had at freeway speed (although tons of other things could cause that including the broken spark plug I had.)

Since the compression checked out fine in all cylinders, I plan to fix all this.  Anyone have any experience here?  Per Bentley,
this would require removing the upper AND lower timing chain covers.  The lower one sounds like a bear.  The vibration damper nut
on the crankshaft pully is at 325 ft/lbs?  How can I possibly hold the crank in place while I try to remove/re-install this nut?
That seems like the hardest part.  I noticed below mention of the chain "stretching."  How is that possible?  A rubber belt I
could see, but a steel chain stretching seems like a long shot to me.

Any help/feedback is much appreciated.

Thanks.

Chris



> Date: Fri, 04 Jan 2002 01:26:34 -0800
> From: jkerouac@domain.elided
> Subject: re:  E28 valve noise
>
> re: E28 Valve Noise:
>     Oil pressure checks are unnecessary, that would be barking up the
> wrong tree.  If there were oil pressure problems the you will likely see
> the oil light glow dimly at idle and go out about 1000 to 1500 rpm.  The
> fix for that is either to replace your oil pump if the pump is weak, or
> to replace the oil pump chain, crankshaft gear, and then shim the pump
> properly so the chain is snug.  Generally, low oil pressure will not
> cause valve taps, valve wear does.
>     I had a 533 that was running great at 225k miles when I sold the
> car, and did need to replace the oil around 200k miles.  There was no
> tap problem, just the oil light coming on as I described above.
> If you have valve noise, the first thing on the old big block motors is
> to adjust the valves.
>     In doing that you may find too much wear on the rocker arm
> eccentrics to get the correct clearance.  If that is the case replace
> the eccentrics.  Be sure to use a new bolt, nut, and washer with each
> new eccentric.
>     Contact a digest advertiser to obtain these parts.
>     Also be sure to replace the valve cover gasket and do not
> overtighten the valve cover nuts.  Its amazing how seemingly loose the
> proper torque for a leak free valve cover is compared to how over tight
> most gas station gorillas would tighten them.
>     You might also be getting some tick from the chain and/or gear if
> the wear is sufficient.  Therefore if you want to get more involved, as
> long as you're in there already, if your valves are this worn its very
> likely the timing chain is stretched and the cam gear is well worn.
> With an engine as worn as yours by replacing the chain and gear you can
> regain some idle smoothness and restore some lost low end torque.
> Changing them is just another few bolts to take off the front cover, and
> connecting the new timing chain to the master link of the old one to
> fish it around in place.  Always tie the chain off with hanger or safety
> wire just to be absolutely sure there is no chance you could drop the
> chain down in the engine, that would put you in deep doo doo, and I
> don't mean your dirty oil.
>     Another suggestion for a high mileage motor would be to take a
> compression check too, only after you have adjusted the valves.
> Good Luck,
> "jk
>
> Date: Fri, 4 Jan 2002 06:26:23 -0500
> From: "Karl Zemlin" <karl@domain.elided>
> Subject: RE: E28 valve noise
>
> I wrote up a response last night, but my email was hosed so I couldn't send
> it.  This reply is much better than what I wrote.  The only thing I don't
> see mention of here is cam wear.  If the oil bar bolts over the cam come
> loose you can lose lubrication at the outer ends of the cam.  While you're
> adjusting the valves, check the cam for flat spots on the lobes at the outer
> extremes.  Chances are it's fine and valve adjustment will take care of it.
>
> When you do the valve adjustment, lean to the tight side.  With my first BMW
> I tried to aim for very light contact on the feeler gauge when adjusting the
> valves.  When I attended my first club tech session, everyone there turned
> and looked at my car when I drove up.  When I stepped out they all said, in
> unison, "You need your valves adjusted".  When the mechanic was adjusting
> them he used a feeler gauge at the low end of the clearance spec (which I
> don't recall ottomh) and had to pull and wiggle a little to get it out from
> under the rocker arm after the eccentric was locked.  I was amazed at the
> difference when he was finished!
>
> Good luck!

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