[Shotimes] Cancer with a twist

[Paul Nimz]

If you are going to drill, use a left handed bit.  You have better than a
50/50 chance of removing the broken bolt and keeping the threads intact.

Paul Nimz
'97 TR SHO
'93 EG mtx SHO


----- Original Message -----
From: "Mark D. Mallory" <mmallory78@earthlink.net>
To: "AutoX-SHOTimes" <shotimes@autox.team.net>
Sent: Wednesday, April 23, 2003 11:41 PM
Subject: [Shotimes] Cancer with a twist


> For those interested in crank cancer, here is a new form that I have not
yet
> heard of.  Typically the timing sprocket works its way loose, which
> eventually wears on the woodruff key, which in turn lets the timing
sprocket
> move more, so and so forth.  This situation is compounded by a leaking
water
> pump which allows things to rust and wear away faster.
>
> I just stripped down the front of my engine (or at least tried to) to
> replace a leaking water pump.  Had a heck of a time breaking the crank
bolt
> free.  I thought it was kind of odd that the bolt would stop the starter
> from turning the engine.  At this time I had the battery hooked up with
> jumper cables, so I figured I wasn't getting enough juice to the starter.
> This is something I have not had a problem with in the past.  Hooked the
> battery up directly to the cables in the car, turned the engine over, and
> presto I heard the bolt break free!  Or so I thought.  Turns out the bolt
> sheared itself at the beginning of the threads.  Not good!
>
> Pulled the crank dampener off and half the woodruff key fell out.  Yes,
> that's right, only half the key fell out.  The key had sheared directly
> between the pulley and timing sprocket.  The part under the dampener had
> about 1/3 of it's width worn away.  Did I mention that I could turn the
> dampener through ~1/4" without moving the crankshaft?
>
> Anyway, after further investigation here's what I suspect happened.  The
> crankshaft bolt must have worked loose allowing the dampener to move
> (similar to crank cancer scenario described above).  I've had a leaking
> water pump (apparently for longer than I should have).  I'm guessing that
> there was an abnormal amount of wear taking place, since there was red
rust
> on the crankshaft, woodruff key, and inner surfaces of the timing gear and
> dampener.  At some point the woodruff key sheared in two, probably from
> excessive vibration due to the crank bolt being loose.  From this time
> forward the crank dampener was free to "rock" back and forth on the
woodruff
> key during acceleration and deceleration.  My best guess on why the bolt
> sheared is that it rusted in place.  I have yet to confirm this.  Lucky
for
> me the woodruff key sheared... there is no apparent wear on the timing
> sprocket or the keyway under the sprocket.
>
> Some may ask if the bolt was cross threaded.  My response would be, I
don't
> think so.  I don't recall if that bolt was removed when I had my tranny,
> clutch, and motor mounts done last.  Can anyone tell me if the dampener
> needs to be removed to install motor mounts?  If it does need to be
removed
> than I have some questions for the mechanic.
>
> Shortly after that service was done, I experienced a shimmy in the front
end
> (only upon acceleration) that I thought was coming from the inner cv-joint
> on the driver's side.  Never was able to isolate the shimmy... until now.
> I'd be willing to bet that the shimmy was in fact the crank dampener
gett'n
> it's groove on.  Chalk that one up to inexperience... the thought that it
> could be a loose dampener never crossed my mind.
>
> Of coarse now, I'm waiting for a crankshaft bolt and woodruff key (found
> using PartsVoice).   Then I get to try and remove what's left of the bolt
> from the shaft.  To do this I've decided on drilling out the bolt and
> re-tapping the hole.  With any luck I won't mess anything up... wish me
> luck!  I've decided against messing with easy-outs, since the risk of
> breaking it is just too great.
>
> Well that's my story for now... I'll keep everyone posted.
>
> Mark Mallory
> Toledo, Ohio
> '95 SHO MTX... broken :(
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