Barry,
I noted similar,
I was replacing the whole system as part of a rebuild. Copper pipes, new
slaves, rebuilt callipers, braided hoses etc. The only thing I didn't change
was the master cylinder seals... Added the DOT5, and after pressure bleading
the whole system felt spongy, as though the master was leaking..
Anyhow, I left the car for 3 months (Don't ask!)
and when I came back things had sorted, and I have driven a couple of thousand
miles with no problems...
Obviously it took a while for the seal to react to the new fluid!
Cheers
Tim
Barry Schwartz wrote:
> Tim -
> Oh, no apologies necessary. I just didn't want anybody thinking that they
> could
> pour a bottle of Silicon based brake fluid in an already Glycol based
> system and think everything was a-OK. I tried pouring a little Girling DOT
> 4 in some used DOT 5 Silicon, and that's what I found - You can shake it up
> all you want and you get a cloudy mixture that eventually settles out into
> a blob of Glycol fluid in the bottom - In fact it's been my experience that
> even changing from Glycol to Silicon one needs to completely flush the
> system with some form of cleaner (I used brake cleaner) and also replace
> ALL the rubber with new. I know that others have been successful without
> doing this, and that's fine. If it works, all the better. In my case the
> rubber was damaged by NOT replacing it and I ended up having to tear
> everything apart and replace all the seals anyway. And I flushed the
> system with brake cleaner before filling. I believe that the swelling
> agents act differently with the various fluids, and that is what caused the
> problem in my case. The fairly new system filled with DOT 4 had sufficient
> time to stabilize and when I switched over to DOT5, different reactions on
> the seals caused them to swell differently then they already had, and
> caused them to fail - One of the seals in the master cylinder almost fell
> apart in my hand it was so soft. At any rate, after I replaced all the
> seals everything has been fine -
> One thing that is notable, and quite a nice difference from the old Glycol
> "fluif" is that the Silicon in the reservoir seems to remain clear. You
> don't get that characteristic blackening of the fluid as you do with Glycol
> based stuff -
>
> Barry Schwartz (San Diego) bschwart@pacbell.net
>
> 72 PI, V6 Spitfire (daily driver)
> 70 GT6+ (when I don't drive the Spit)
> 70 Spitfire (long term project)
--
Tim Dafforn
Structural Medicine
Department of Haematology
CIMR
University of Cambridge
Wellcome-MRC Building (Level6)
Hills Road
Cambridge
CB2 2XY
Tel. (01223) 336829
Fax. (01223) 336827
http://smokeroom.cimr.cam.ac.uk/
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