I have cleaned and rebuilt all components for brake and
clutch on my '70 E-Type and had intended to use DOT 5 fluid.
Now I see DOT 5.1 being offered, what’s the difference? Now
that I have traces of DOT 5 in the lines, if I use the DOT
5.1 do I need to flush everything with cleaner first?
Primary reason is to prevent brake fluid from attacking the
paint.
In reply to a message from retiredfd sent Sun 22 Dec 2013:
They are totally different.
DOT 5 is silicone-based and does not eat paint nor absorb
moisture. It also has other characteristics that some like
and some don’t.
I believe that DOT 5.1 is an extension of DOT 3 & 4 but
with a higher boiling point. So far as I know it will have
the same affect on paint as the earlier iterations.
FWIW – I converted my E-Type to DOT 5 (which I have used
in my other Brit cars for 15 years or so) and have had
excellent results.–
Geo Hahn 1969 OTS 4.2
Mt Lemmon, Arizona, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from retiredfd sent Sun 22 Dec 2013:
Hi Art,
Dot five is silicone based and will not eat your paint,
Dot five point one is Glycol based and will eat your paint.
There are trade offs when using DOT 5 fluid, I used it on my
'68 and will continue to do so but, while it doesn’t absorb
water it is difficult to flush the water that naturally
accumulates in the system as it migrates to the lowest points
in the system and corrodes the components at that point. I
have found that I still have to bleed the system every 2-3
years even with the DOT 5 fluid and I will drain my will woods
from the bottom then top bleeders. I have also noticed that
the brake pedal has a very slight ‘stickiness’ to it’s feel.
When I restored the '68 I didn’t want to risk paint damage and
I’m glad I did because I had several fittings that persisted
in leaking till I reworked them and I think I would have had
paint damage from Glycol based fluid.
I really don’t see much difference between DOT 5.1 and DOT 4
so will leave to others who know much more about the chemistry
of those fluids.
Cheers,
Lynn–
The original message included these comments:
I have cleaned and rebuilt all components for brake and
clutch on my '70 E-Type and had intended to use DOT 5 fluid.
Now I see DOT 5.1 being offered, what’s the difference? Now
that I have traces of DOT 5 in the lines, if I use the DOT
5.1 do I need to flush everything with cleaner first?
Primary reason is to prevent brake fluid from attacking the
paint.
Art.
–
Lynn G.
68/85 ots, 73 2+2, Boise, Id., United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Geo H sent Sun 22 Dec 2013:
Yeh I think thatGeo is right. This makes me feel that the
brake fluid industry is all screwed up.There is no way that
a new extension of DOT 3 and 4 should be 5.1 when silicones
are already categorized as Type 5. It would better be 4.1 .
I can see folks getting the types inter mixed, with the
ensuing disaster!!–
The original message included these comments:
They are totally different.
DOT 5 is silicone-based and does not eat paint nor absorb
I believe that DOT 5.1 is an extension of DOT 3 & 4 but
with a higher boiling point. So far as I know it will have
Geo Hahn 1969 OTS 4.2
–
John M Holmes 1973 E Type SIII Supra 5Sp, 70 SII OTS 05XJ8L
Ontario, Canada
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from John M Holmes sent Sun 22 Dec 2013:
Puzzled over that myself.
But as to mixing it is my understanding that you need to have all
new seals and hoses to convert to DOT 5, ie flushing out the old
DOT 3/4/5.1 isn’t sufficient. I also understand that you can,
however, flush out DOT 5 with glycol based fluids to convert back
without having to change out all the rubber components. It is for
this reason I’ll be charging my newly rebuilt braking system with
silicone first. If the result is not to my liking I’ll go back to
glycol, but like Geo and Lynn I’d rather avoid its corrosive
properties.–
The original message included these comments:
brake fluid industry is all screwed up.There is no way that
a new extension of DOT 3 and 4 should be 5.1 when silicones
are already categorized as Type 5. It would better be 4.1 .
I can see folks getting the types inter mixed, with the
ensuing disaster!!
–
Nick Saltarelli '68 Cdn mkt E-type S1� OTS, '54 XK120SE OTS
Niagara, Ontario, Canada
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from N�ck sent Sun 22 Dec 2013:
Back in the early 80’s I replaced the brake fluid in my 79
Volvo 244DL with Dot 5, all I did was flush it out and replace
with the DOT 5. While my experience is strictly anecdotal, I
kept the car another 6-7 years and never had a problem. Along
that same line I mixed used DOT 5 and DOT 4 in a jar and let
it sit for months and they both remained separate and neither
‘jelled’, granted these are not the conditions of hot and cold
that would be experienced in a brake system, it still makes me
wonder.
Waiting for the Chemists to (John H.) to chime in.
Cheers,
Lynn–
The original message included these comments:
Puzzled over that myself.
–
Lynn G.
68/85 ots, 73 2+2, Boise, Id., United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from John M Holmes sent Sun 22 Dec 2013:
If you read the DOT specs, DOT3, DOT4 and DOT5
specifications differ primarily in the minimum boiling
points, NOT the composition of the fluid itself. It appears
to me that for many years the only fluids that could meet
the DOT5 specs were silicone-based, but DOT5 does not
REQUIRE DOT5 fluids to be silicone based. The DOT 5.1
designation appears to have been added as an after-thought,
to help reduce confusion. At this point, silicone-based
fluids are required to be labelled as either ‘‘DOT 5 SILICONE
BASED’’ or ‘‘DOT 5.1 NON SILICONE BASED’’, to further reduce
confusion. There is a further requirement for silicone-
based fluids to be purple in color, while non-silicone
fluids are required to be between amber and cilear in color.
But, simply, the ‘‘5’’, by itself, says NOTHING about the base
chemistry of the fluid, and was never intended to. The
higher the number, the higher the boiling point.
Eventually, there will likely be a DOT 6…–
The original message included these comments:
Yeh I think thatGeo is right. This makes me feel that the
brake fluid industry is all screwed up.There is no way that
a new extension of DOT 3 and 4 should be 5.1 when silicones
are already categorized as Type 5. It would better be 4.1 .
I can see folks getting the types inter mixed, with the
ensuing disaster!!
–
Ray Livingston - '64 OTS Santa Cruz, CA
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–