Re: M5 T/Chain (detailed) (archive)

1. Contact Brett Anderson at http://www.koalamotorsport.com and use his Pay-per-Incident service to get a master tech's advice. It is only $25 if you wait 3 days for his opinion and more if you want it ASAP.

2. It is possible the tensioner piston/bore clearance is going up due to wear and it is bleeding down. I would recommend replacement, but this is not a trivial matter and you need to understand the process (not just the procedure) fully before you do it. The tensioner is hydraulic.

3. MOST IMPORTANT. Do not park the car in gear, if this is what you have been doing. If you park it in a forward gear nose-uphill you put force on the slack side on the chain and bleed the tensioner down. Park in neutral with handbrake.

4. Unfortunately, there are a number of reasons you could have the noise and the cheapest is tensioner replacement. You slop numbers are within those for my new items.

5. Don't know about tech time. Ask Brett to give you an estimate.

6. Parts:
TIMING COVER
a. Chain, $40-50
b. Timing Cover Gaskets, $10-20
c. Guides (top and bottom), $40-50
d. Guides (rubbing), $300-350. Examine and decide.
e. Sprockets, $100-120 each.
f. Various seals, etc., $50 max.
g. Crank bolt, $20?
h. Crank Tool Rental from Brett for DIY, $150-200

HEAD REMOVAL RELATED
a. Gasket set, $175-200
b. Head bolts, $100-150

That should be pretty much it. Note that if you remove the head you might want to have a valve job done and I paid $640 for mine. Contact http://www.elephantmotorsports.com for parts.

I wouldn't bother with the Dinan gear, but the Fahey hub sounds like a good, but expensive idea. Perhaps if you're not racing the auto, the stock hub is good enough, but I don't know as my E34 does not have this issue.

Neil Deshpande
http://www.neilwerke.com

***

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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