Re: sodium-filled exhaust valves?

[Jorel Jackson <jorel140@yahoo.com>]

--- SailingFC@aol.com wrote:
> jorel140@yahoo.com writes:
> 
> > Why do they put sodium in exhaust valves? Does
> this
> > have somthing with cooling? Just came across this
> in
> > the Bentley, along with the instructions not to
> > dispose of more than ten at a time in a bucket of
> water.
> > 
> 
> Sodium is used for cooling.  The inside of the valve
> stem is hollow and is 
> partially filled with sodium.  When below ~98C, the
> sodium is solid.  As the 
> engine heats up and the valve goes above 98C, the
> sodium liquifies and starts 
> sloshing around in the stem.  This sloshing from top
> to bottom, actually 
> helps transfer more heat than if the stem was solid.
>  By sloshing to the 
> upper half of the stem, more heat can be transfered
> out of the valve, into 
> the valve guides and head.
> Sodium reacts violently to water and will actually
> "burn" if it contacts 
> water.  Not too sure what is meant by the "ten at a
> time in a bucket of 
> water" since the sodium is sealed inside, unless
> there may be holes or cracks 
> in the valve stem.
> Sodium valves are a good thing.
> HTH.
> 
> -Dick-
> 78 Scirocco
> Original Owner
> http://member.aol.com/sailingfc/
> 

This reaction, I presume from the instructions, occurs
after sawing the valves open with a hack-saw. They say
do not use a power saw. They actually tell you to
throw them in the water and stand clear. It looks like
only the 16V uses sodium-filled exhaust valves?

I thought it must have somthing to do with cooling.
Thanks for the info.

=====
Jorel Jackson
1987 16v & 1985 8v Sciroccos
2000 Neon ES

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