[s-cars] Bullet Dodging

[John Tilden]

Bob Writes:
> While removing the belt - "Hmmmm - the toothed belt pulley is a bit loose
> on the end of the crank shaft - let's pull that sucker out of there and
> have a look at it."
>
> The pulley came out nicely and exposed the fact that the key which locks
> the pulley has been nearly completely sheared off.  A light touch pulling
> on the key with a finger tip broke it off into my hands.  There couldn't
> have been more than 0.01 mm of metal holding the key in
> place.  Additionally, there is evidence of some rubbing of the pulley
> against its seat on the crank.  It has been shifting its position
> (rotationally) by nearly the width of the key (or about 1.5
> belt  teeth).  This is more than enough to have an effect on the timing.
>
> If that key had completely sheared off it would have had the effect of a
> broken belt.  The condition it was in has me wondering if I'd have even
> made it home.  A new pulley is ordered and will be here tomorrow.

My Mechanic has found several instances of failed or near failing Crank
Pulley Keys!
One which was "glued" back together with epoxy by a previous mechanic!
Pulley, Bolt, Crank and remnants of the key! Imagine the expletives that
were used to get that apart! He broke two 1/2" drive Snap-On Breaker Bars
getting the Bolt out! Finally bought a 3/4" drive breaker and socket to get
it apart!
I am going to make a practice of replacing my Crank Pulley every time the
timing belt is replaced!
The "Key" is an integral part of the Pulley which is manufactured using
Powdered Metal Technology, basically pressed and sintered powdered iron.
This technology is great in compression and in large sections, but the key
is pretty thin and has some notchy geometry which will tend to propagate
cracks, so out with the old and in with a new one! The good news is they are
"only" about $45.00 so not a big cost item.
Just add this to the other parts you replace "when you are in there"!
Timing Belt, Water Pump, Timing Belt Tensioner, Serp Belt, Serp. Belt
Tensioner, Cam Position Sensor, etc, What did I miss?

By the way, connecting rods on a number of new automobiles are made using PM
technology!
As I recall, even the new Water cooled Porsche rods! please correct me if I
am in error!
They are even proud of the fact that they "Crack" them into two pieces after
the big end is machined to diameter, maybe OK for a Honda, but....!

John

John Tilden
Tilden Consulting Services
2820 164th Ave N.E.
Bellevue WA 98008
(425) 881-2895 Office
(206) 240-5318 Mobile
j.n.tilden at comcast.net