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silicone Dot 5 break fluid

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8 years 6 days ago #39405 by David Moult
I am thinking about putting this in the car starting with the clutch. When it first came out in the 70's people said it was spongy and corrupted seals. I see Automec sell Dot 5 and claim the US army uses it so if that is true it can't be hopeless. Its the water repellent nature of it that is interesting.
Any practical first hand recent knowledge?

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8 years 6 days ago - 8 years 6 days ago #39406 by Pete Pearson
As far as I know the rubber used in seals intended for DOT 5 is different for those intended for Dot 4. It will still be the same basic spec as it was in the 70's otherwise it would have been called DOT something else.

I suggest that those vehicles the US army has use seals specifically designed for use with DOT 5.

I certainly wouldn't put DOT 5 fluid in my X1/9's standard hydraulic system despite its non-hygroscopic properties.

Edit

It seems that DOT 5.1 is compatible with DOT 4 fluid and seals.

Sorry for the Wikipedia link but in this case I think it is true.

en.wikipedia.org/wiki/DOT_5.1
Last edit: 8 years 6 days ago by Pete Pearson. Reason: hygroscopic - not hydroscopic

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8 years 5 days ago #39408 by Ian Thomson
I have been running with Automec Dot 5 silicone brake fluid in my X1/9 for over 15 years without any problems. You need to make sure that you get all of the normal fluid out of the system when you make the change over and you cannot top-up with normal fluid without losing the advantages of the silicone stuff.

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