Re: Opti musings... (was Re: more details sbc in place of lt1)

[Shannen Durphey <shannen@grolen.com>]

Not every bad opti is rusty.  I know of some that have failed
immediately after the engine was washed.  I think that the opti will
suck in moisture through the three holes that Andrew mentioned.  What
I think does it is spraying cold water on a hot opti.  GM had similar
troubles with aluminum driveshafts in pickups.  Drive on a long road
trip hauling a boat, then back into a cold lake while the driveshaft's
warm.  Water would get sucked in through a vent in the rear of the
driveshaft.

I flush the cooling systems on LT1 cars and haven't lost an opti yet. 
Can you hear me knocking?  : ) But I do the job when the engine's
cold.
Shannen 

Bruce Plecan wrote:
> 
> Odd.
> The two early ones I took apart had stainless discs.
> Hmm, wonder if it was a coating of something like SS that failed.
> Grumpy
> 
> > Well, Garfusion, I think the Lo-res pulse was for when the inevitable
> > rusting of the disk happened, and you lose the hi-res disk pulses. ;^)
> > Seeing how they mounted the opti right below the water pump, didn't seal
> > it against the elements at all, and hardly vented the '92-'94 units (3
> > teeny holes in the back plate), they're quite good at holding pump
> > seepage, and the little metal slotted disk is quite adept at rusting,
> > and rust can easily fuzz up those tiny holes (heavy spark air ionization
> > plus coolant plus bare metal? yikes!). Car will keep running (not that
> > great, and with a DTC) when you lose the hi-res pulse, but lose the
> > lo-res pulse, and that's it. Car doesn't run, and it's new opti time.
> >
> > I think it was a good idea put together wrong. Accurate timing, yes, but
> > that rust thing is sure a killer. They should've used a hard plastic or
> > a stainless disk. And at nearly $300 each, them buggers ain't cheap.
> >
> > -Andrew
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