** Reply to message from "Pat Leask" <pleask@telus.net> on Fri, 24
Aug 2001 20:21:29 -0700
Pat,
As far as I can tell, brake fluid now comes in the following flavors:
DOT 3 Glycol Based: corrosive to paint & rubber, highly water
absorbant.
DOT 4 Glycol Based: corrosive to paint, does not absorb water as
readily as DOT3, has a higher boiling point than DOT 3, can be mixed
with DOT 3.
DOT 4/3 Glycol/Poly-glycol Based: Labeled "Synthetic" and "exceeding
DOT 3 and DOT 4 specifications", it is still corrosive to paint, but
highly non-absorbent of water, and has a higher boiling point than DOT
4. It can be used in systems having ABS, and can be mixed with
standard DOT 4 and/or DOT 3 fluids.
DOT 5 Silicone Based: non-corrosive to paint, does NOT absorb water,
has a slightly lower boiling point than DOT 4, and CANNOT be mixed
with DOT 4 and/or DOT 3 fluids. If converting from a glycol based to
a silicone based system, the system should be drained of all glycol
based fluid, then should be completely flushed with denatured alcohol,
then flushed with the silicone based fluid, then filled with the
silicone based fluid, properly bled, and topped-up with silicone
based fluid.
DOT 5.1 Glycol Based: corrosive to paint, highly non-absorbent of
water, compatible with both DOT3 and DOT4 fluids, higher boiling point
than DOT4, used in systems having ABS. Note: I have never seen
anything specifically labeled as "DOT 5.1" on an auto parts store
shelf here in the U.S., but it mysteriously specs out like the
synthetic stuff that I listed as DOT 4/3 above.
I have DOT 5 fluid in my 280i and have not experienced any problems
with it.
George
1985 280i FHC #BFH1184
TVRCCNA Member #1090
> I have a 2500M with all new brake cyclinders, lines etc.
>
> I need to know what brake fluid to put in this thing. Some say that DOT5
> (Synthetic ?) is great, others say it is terrible. We all know what DOT4
> (the real stuff !) does to paint but I know it works......
>
> Help please ?
>
>
> Thanks, Pat
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