I didn't want to get too in-depth with my first reply, as I seem to be able
to do that pretty easily. You are correct the glycol-based fluids are
hygroscopic and absorb water. This water can boil, lowering your brake
fluid boiling point in use, or cause corrosion internally in
storage. Using silicone, then, the water would rise or sink in the system
and gather in one spot and corrode that area...or this seems to be what
would happen. However, I've talked to a lot of people who store their cars
for a long time and have not changed their silicone fluid in a decade and
have never had any corrosion issues...so my guess is that the water is not
in contact with areas that corrode easily or the silicone forms a barrier
on the metal...just a guess, there though, on the last point.
By law, all DOT brake fluid must be compatible...ie, if you mix, your
brakes still work. This is not to recommend the practice by any stretch (ie
don't do it on purpose)..just to say that if you do mix, your brakes will
not suddenly stop working and cause a catastrophe. Sorry if that was unclear.
At 11:35 AM 11/19/01 -0800, you wrote:
>Hi, Bill---I always believed that DOT 3-4 and the 5.1 glycol based
>fluids were supposed to absorb water that can accumulate in the brake
>system. The purpose, as I understood this is that when water is allowed
>to fall out of suspension (as when there's too much for the fluid to
>absorb) that is when corrosion can start. If this hypothesis is true,
>silicone fluids surely won't help the cause, and in fact may encourage
>deterioration because of its inability to absorb the natural occurance
>of condensation, thru brake parts heat cycling.
>
>I don't want to start another debate on silicone VS. glycol fluid, but I
>was surprised to see you write that these two fluids must be compatable,
>by law.
>
>Dick
>
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>Date: Mon, 19 Nov 2001 09:59:30 -0500
>To: 6pack@autox.team.net
>From: William Whitmoyer <wwhitmoyer@samsonite.net>
>Subject: RE: DOT5 survey
>Mime-Version: 1.0
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>Reply-To: William Whitmoyer <wwhitmoyer@samsonite.net>
>
>Unless you plan to race the car, DOT5 (silicone, not DOT5.1) is an
>excellent choice for brake fluid for "extra" cars that see a lot of
>storage. Not only does it leave paintwork intact if it spills, but it also
>resists moisture absorption and thus protects internal brake surfaces like
>caliper pistons. It does, however, readily absorb air, which is why some
>people report spongy pedals...you do need to be extra diligent when
>bleeding. This air absorption (air compresses, unlike brake fluid) is one
>of the main reasons DOT5 is not recommended for racing. The clutch lines
>are much less stressed, especially heat-wise, so DOT5 works well in them too.
>
>Usually, people switch to silicone after rebuilding the brake
>system. Another way to do it is to run denatured alcohol through the lines
>to clean out the old fluid. Some people just pour it in, but you are
>cheating yourself of the full benefits of silicone..mixing will work,
>though, as it's a legal DOT requirement that all brake fluids must work
>with every other type of brake fluid.
>
>
>
>---------------------cut-------------------------
>
>Date: Sat, 17 Nov 2001 21:11:14 -0500
>From: Jim Henningsen <jdhenn@cfl.rr.com>
>Subject: re: Dot 5 and Paint Codes
>I use Dot 5 in my six. Switched over when I redid all of the brake
>components. I haven't noticed a difference with normal around town
>cruising and I like the fact that my new paint job will be better off.
>My two cents
>By the way. My 6 was originally brown (maple brown I assume) but my ID
>plate says paint code 73. I haven't been able to find this code in any
>of the books. Any on got an idea or is TRF code list wrong. They show
>maple brown (1975) as 83.
>
>Jim
>75 TR6
>80 TR7
>Kissimmee, FL
>
>- - ----- Original Message -----
>From: "R. Ashford Little II" <ralittle2@mindspring.com>
>To: "Georgia Triumph Club" <gatriumph@gatriumph.com>
>Sent: Friday, November 16, 2001 2:02 PM
>Subject: [gtr] DOT5 survey
>
> > Does anyone use DOT5 in their clutch or brake system? I am
>contemplating
> > switching and would like some feedback.
> >
> > Thanks
> >
> > Ashford
>
>
>
>William Whitmoyer
>69 TR6
>90 BMW iX
>91 CRX Si
William Whitmoyer
69 TR6
90 BMW iX
91 CRX Si
|