Can old brake fluid be dried?

[Lee Ann]

Hi All-

I understand that an old bottle of brake fluid can absorb moisture from the air (hygroscopic). Would it be possible to dry it out (using a solid drying agent such as molecular seives or calcium chloride (pellets), CaCl₂) and then use it without problems? Has anyone ever tried this before?

I have a couple bottles of brake fluid that have been sitting on the shelf for a couple years. I foresee a front brake job in my future (my SC2) and I really don’t want to waste it, if I don’t have to.

Thanks for your response.

Topic

[Lorrin Barth]

I’m a chemist so I’m not going to say there isn’t a way. However, there isn’t any fluid in the car more important than brake fluid. You want the best. So, throw it away.

A lot of the stuff sold is kinda wet. Hence, the low boiling temperature advertised on the container. But you can buy dry fluid if you search for it.

[Paul]

I’ve used molecular sieves for drying solvents, but I would not attempt it. The sieves will probably cost more than new fluid, need a 300-350C oven for activation/regeneration. Also, it’s possible that the sieves may contaminate the fluid – I’ve had sieves burst and disintegrate and I had to discard the resulting mess.

Even in a sealed container, oxygen has probably permeated the container wall over time and possibly degraded the fluid too.

[Lee Ann]

[quote=”barneyb” post=94513]I’m a chemist so I’m not going to say there isn’t a way. However, there isn’t any fluid in the car more important than brake fluid. You want the best. So, throw it away.

A lot of the stuff sold is kinda wet. Hence, the low boiling temperature advertised on the container. But you can buy dry fluid if you search for it.[/quote]

Good point-one of the most important fluid…

I will not try to use it but I think I may try to dry it just out of curiosity. I have been away from the lab too long (and miss it)!

Thanks for the input!

[Lee Ann]

[quote=”Hanneman” post=94521]I’ve used molecular sieves for drying solvents, but I would not attempt it. The sieves will probably cost more than new fluid, need a 300-350C oven for activation/regeneration. Also, it’s possible that the sieves may contaminate the fluid – I’ve had sieves burst and disintegrate and I had to discard the resulting mess.

Even in a sealed container, oxygen has probably permeated the container wall over time and possibly degraded the fluid too.[/quote]

Yeah, good point-cost, container-fluid degradation. Calcium chloride is cheap.

Anyway, it was just a thought. Thanks for the interesting responses.

[Author]

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