[Healeys] Silicone DOT5 brakefluid for the 100

Alan Seigrist healey.nut at gmail.com
Mon Nov 9 18:04:29 MST 2009


Eric / Rick  -

This happened to me in 1987 with my BJ8 when I tried to switch to Dot 5 (it
was purple color).

All my seals went bad and I had to rebuild my complete brake system.  I
think the new silicone fluids are much better at matching the swelling
characteristics of Dot 3/4, so probably less of a problem now.

Alan

'52 A90
'53 BN1
'59 Jag Mk IX
'64 BJ8


On Tue, Nov 10, 2009 at 5:31 AM, Eric (Rick) Wilkins <e-wilkins at cox.net>wrote:

> I've only seen anecdotal evidence of the so-called degradation of existing
> rubber seals by changing to silicone fluids.
>
> Many sources say there is no worry at all. Others say that external parts
> like boot seals are susceptable to the silicone fluids.
>
> Some sources even list the Dot 3-4 fluids as being "compatible" with Dot 5
> (silicone)
>
> Go figure.
>
> Wilko
>
>
> On Nov 9, 2009, at 12:17 PM, Richard Ewald wrote:
>
>  Do you have any kind of authoritative cite for this claim, or is this
>> something that everyone just "knows"?  Inquiring minds want to know.
>> I have never heard this before.
>> Rick
>>
>> Sent from my iPhone
>>
>> On Nov 9, 2009, at 6:47, Oudesluys <coudesluijs at chello.nl> wrote:
>>
>>  Tom,
>>> You should never fill up with DOT5 if you previously used DOT3 or 4. You
>>> run the very serious risk that the seals will perish and the system will
>>> leak like a sieve.


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