[Roadsters] DOT5 (was: Clutch Question)

[Gary and Cindy Ault]

Richard,

I have been having trouble getting messages FROM the list -- some show up 
days after they were published, so I don't know whether my earlier response 
on this issue even made it to the list.

Several years ago, I replaced the DOT3 fluid in my brake and clutch systems 
with DOT5 (silicone).  I have no clue what DOT4 is, but I don't think it is 
silicone.  I drained the original fluid, flushed the systems thoroughly with 
denatured alcohol, then flushed them thoroughly with silicone fluid.  No 
leaks or other problems ever since.  No pedal softness, either.

Gary Ault


----- Original Message ----- 
From: "Richard Schnoor" <machworx at gmail.com>
To: "John F Sandhoff" <sandhoff at csus.edu>
Cc: <datsun-roadsters at autox.team.net>
Sent: Wednesday, February 20, 2008 6:30 PM
Subject: Re: [Roadsters] DOT5 (was: Clutch Question)


> Its been a while since I have worked on my roadsters, but I have some
> questions: Forever DOT3 was the standard brake fluid which is hygroscopic
> (absorbs water from high humidity air) which then ends up rusting your 
> brake
> calipers. Some one told me about DOT 4 which was silicone based & was not
> hygroscopic so rusting wasn't a problem for a seldomly driven car. When I
> changed over to "4" my brakes were extremely spongy & was accordingly was 
> a
> problem with this type of brake fluid. I even built a pressurized auto
> bleeder so I could bleed my brakes alone but resulted in no reduction in
> sponginess. So what is DOT 5 & 5.1? Do these new fluids address the
> sponginess or rusting problem?
>
> On 2/19/08, John F Sandhoff <sandhoff at csus.edu> wrote:
>>
>> Keep in mind that DOT5 has been reported to be harder to get a
>> clean system bleed with. Power bleeding seems to be more
>> effective than other methods. Also, DOT5 will find its way thru tiny
>> seal imperfections so a system that's leak-free on DOT3/4 may end
>> up leaking on DOT5.
>>
>> I don't know how DOT 5.1 behaves. It's apparently not silicone based
>> like 5.
>>
>> I personally use DOT4 - Castrol GT/LMA for years and years but have
>> switched to Valvoline synthetic DOT4.
>>
>> -- John
>>     John F Sandhoff   sandhoff at csus.edu   Sacramento, CA
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>
>
> -- 
> Richard Schnoor P.E.
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