Re: M5 T/Chain limited insight (long) (archive)

Mark - can't help you with the specs you are asking about. there was a pretty decent article in the roundel (e30 m3 issue) a while back concerning the S14 motor and timing chain issues - these apply to the S38 from what i understand as well. after hearing about the expense involved if a timing chain fails, i became a bit worried and did a little checking. acatually it's the plastic rails that the chain rides on that wear enough to allow the chain to skip a tooth on and well you know the rest. the motor does have a hydraulic tensioner as well. if i recall, total for just parts alone to do the chain and tensioners was about a grand from maximillian (and they have great prices!). i put that job on hold for a bit - started driving the car less and stopped worrying as much. i didn't research the job any more, but i would imagine the crank hub will have to be removed to do this. in which case i would only be inclined to put a frank fahey bulletproof crank hub in it's place. and hell while you're in there, why not do the cam gear upgrade. anyway, you can see this is getting expensive - so like i said i've put it on hold until i come into a small fortune. let me know if you're interested in the S14 article. hope this helped - jeff h

In light of recent events, this seems pretty trivial, but life goes on.
Car makes noise on cold start that could be t/c, a tensioner or piston slap. Pulled cam cover to inspect. Chain has approx +/- 6mm up and down play (perpendicular to deck w/top rail removed) This does not seem excessive compared to other T/C engines I've done. Also has approximately 1-1.2mm axial slop (front to rear slop within chain itself. This does seem excessive.) What is the typical failure mode of these chains? Are any of the tensioners hydraulic. (Maybe check valve is bad and it takes a while to pump back up?) The following info would be very helpful.

Reprint of appropriate pages from manual (if available, will gladly buy these!)

Looseness (wear) spec for chain.

Any info about tensioners and failure mode.

Approx. time for skilled mechanic with well equipped shop to do job?

Required parts list

Any recomended enhancements (Dinan exhaust sprocket? Fahey hub?)

I am planning to do chain and tensioners if needed but want to ensure I fix root cause of problem. Any help or advice would be appreciated.

TIA, as always
Mark

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