Why o-rings fail:

http://hydraulicspneumatics.com/200/TechZone/Seals/Article/False/6504/TechZone-Seals

Compression set
Failure pattern: Common to both static and dynamic sealing
applications, compression set failure produces flat surfaces on both
sides of the O-ring's cross section.

Problem sources: The selected elastomer has poor compression-set
properties . . . Low heat resistance of material . . . Excessive
swelling of O-ring material in system fluid . . . Too much squeeze to
achieve seal . . . Incomplete curing (vulcanization) of the O-ring
material during production.

Suggested solutions: Use a low set elastomer . . . Specify an O-ring
material that resists both operating and friction-generated heat . . .
Re-check O-ring material compatibility with system chemicals . . .
Reduce O-ring squeeze if possible . . . Inspect incoming O-rings for
correct physical properties.

So under the circumstances, I'd hazard a guess that the Honda car o-
ring failed because the motor was overheated thereby exceeding the
design of the o-ring.

And regarding lubrication: <http://www.theoringstore.com/index.php?main_page=index&cPath=343
 >

Me? I use Dow Corning 33. A tube of it will last you and your children
and your children's children's lifetimes.

Jim

It's really easy to fall into the trap of believing what we do is more
important than what we are.
--Fred Rogers

On Dec 1, 2012, at 6:58 PM, Scott Daniel - Turbovans wrote:

> How come then ...
> on a 5 year old Honda car ..
> before I even saw the car...just hearing about the coolant smell the
> customer was experiencing ..
> I knew it was the thermostat o-ring ?
>
> ( And this was after a fancy shop said they couldn't find anything ..
> but I knew, just onthe phone with the customer it was very likely the
> thermostat o-ring ..
> and it was. )
>
> Because ...o-rings don't seal that well after a while.
>
> there are SO MANY things that are 'supposed to work' in the
> theoretical
> world ..
> but inthe Real World ..they don't..