Brake Fluid Question

I suppose you could always keep the fluid. Just by being exposed to the air in the container will cause some water to be absorbed into the brake fluid. To remove the water you could heat to a little over 212 F at atmospheric pressure. The water will boil off. This is one way things (liquids) are separated in chemical plants. It's called distillation. Would not think anything else would boil off as the fluid is capable of withstanding temperatures that low.

I don't do it myself but it seems to me it should work.

 

How about transfering the new fluid into smaller container. Fill it up to the top of the smaller container, cap it with an air-tight seal.

To preserve some of the polys and sealers I use for displays/furniture and woodwork I'll crush the bottom of the can, forcing the remaining sealer closer to the top and putting the lid back on...ultimatley less room for "air" in the can.

 

Hmmm, heating it is an interesting idea but I am wondering how you would go about that without exposing it to atmospheric water vapor. Putting the container in a pan of boiling water is obviously out.

But the real question is: why are you topping off your brake fluid? does the system have a leak? If not, the lowering of the level is just due to pad wear and the system is designed to have enough capacity to allow for that. If you add fluid now, when you replace the pads there will be too much fluid in the system and the reservoir will be over filled and maybe even overflow.

I go through this every time I have my oil changed: the guys want to add brake fluid and I stop them.

Persnoally, I run a can of brake fluid through my system every year. Just get a bit of clear hose, a clear bottle, like an empty small plastic soda bottle. Siphon the old fluid out of the reservoir into the bottle, refill the reservoir with fresh fluid. Go to the right rear, attach the hose to the bleed fitting, put the end into the bottle and make sure it's submerged in the old fluid. Open the bleeder and have a buddy pump the brake pedal. The hose in the fluid stops you sucking air into the system so none of that push, open, close, release rigamarole. Just open and pump until the fluid runs clear then pump a few more times. Close the bleeder and go on to the left rear then right front then left front, same procedure. Takes 20 minutes including the jacking and pulling wheels, or an hour including beer breaks!

 

Simple. Put the brake fluid in a metal container (obviously clean) and heat. The separation of the water from the fluid occurs very quickly at the elevated temperature. Then pour the heated fluid back in a smaller container and seal for storage.

The absorption of water vapor from the air is a slow process. It relies on the diffusion mechanism which is always slow. You're talking about orders of magnitude in time difference between the two processes.

The idea of putting in a smaller container is a good one.