Dot 4 dot 5 or dot 5.1?

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Dot 4 dot 5 or dot 5.1?

Postby bedfordbad » Thu Aug 20, 2015 10:17 pm

I'm ready to put brake fluid into the pick up and as it's a totally new albeit some new old stock parts which fluid should I use?
Probably this system was designed with dot 3 in mind but I'm aware brake fluid has moved on a bit since 1976. Should I try another perhaps less corrosive fluid?
Steve
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Re: Dot 4 dot 5 or dot 5.1?

Postby 1972nail » Thu Aug 20, 2015 11:54 pm

My understanding is, and I my be wrong, that it's not the fluid that is corrosive but the water that it absorbs. I was tempted to use Dot 5 or 5.1 silicone but as many of my parts were nos and built up in the factory with Dot 3 or 4 as a lubricant I went for Dot 4. Dot 4 and Dot 5/5.1 don't mix.

Changed every couple of years Dot 4 is OK. When it absorbs moisture from the atsmosphere it becomes corrosive and 'boils' at lower temperatures causing brake fade in high performance applications. Dot 5 and 5.1 don't absorb moisture.

I don't keep opened bottles of Dot 4 for long as it will absorb moisture and age just as quickly as the fluid in the braking system. I replace the Dot 4 every couple of years in my cars with fluid from fresh unopened bottles and have had no problems with corroded cylinders, even in our Minor which doesn't have effective seals to keep moisture out of the cylinders.
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Re: Dot 4 dot 5 or dot 5.1?

Postby bedfordbad » Fri Aug 21, 2015 6:10 pm

Thanks for that David, changing brake fluid every 2 or so years just seems one of those jobs thay i never have time to do :imsmiling:
i think i will just go for the dot 4 and keep an eye on it,,, cheers
steve
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BEDFORD HA 130 TNN514R
VARIOUS HA VANS AND ROMA`S FOR SPARES.
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