Re: Coating o-rings with brake fluid?

[jlandry@domain.elided (John A. Landry)]

When the truth serum kicked in, fly4scout@domain.elided (mike d ryan) blurted
out...

>	I'm about to install new water pipes on my 345 (between the heads and
>the water pump), and the book says, "Coat seals (rubber o-rings) with
>hydraulic brake fluid and install ...".  Has anyone coated new o-rings
>with brake fluid before installation?  I'm tempted to coat the o-rings
>with aviation form-a-gasket or copper sealer before the install.  With
>brand new pipes and o-rings, the fit is fairly tight, but coating with
>brake fluid?  I don't understand the reason for doing this.  Will the
>brake fluid cause the o-rings to expand, improving the seal?  Sharing any
>ideas or experience with this would be appreciated.

Mike,

In the case of using brake fluid to coat the water pipe o-rings, the brake
fluid is a fairly good *temporary* lubricant.  I've seen recommendations like
this in other repair manuals over the years.  Brake fluid doesn't attack the
rubber like some lubricants can and is acceptable for that purpose.  Brake
fluid is a logical suggestion because most mechanics are going to have it
around handy.  However, a more modern high tech lubricant would be a *thin*
film of silicone grease.  You would smear the seal and inside of the hole with
a film of the silicone grease and installation would be a breeze.  I use
silicone grease pretty much on any o-ring installation.  The neat thing is
that it's impervious to water and non-hardening... so it will make disassembly
easier years from now.

Take care,

John L.
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