How long does brake fluid keep in its container?
 

I bought a litre of ATE super blue fluid about 4 years ago and completely flushed out my brake system. I still have about 1/3 of a container left.

Is this stuff still good because of the metal container or should I just recycle it at this point?

Obviously fluid in metal is better than plastic, but does anyone have any rules of thumb for how long it can be used after it has been opened?

I probably have 5 or 6 different bottles of fluid in my garage because I just buy new stuff all of the time and just leave the left over in the container forever...

recycle anything that's been opened for more than a few months, if you live in the desert longer by the coast shorter

it would seem ok to use after a long time... assuming it was open for a total of 5 minutes during various fluid fill operations.. and then closed tight in a metal can..
Yes, it was exposed to air with some humidity for a short period so it did absorb some water.. but I'm guessing not very much.. I'm not a brake fluid expert just commenting.. because I have various cans around the garage also. Could be that the "exposed" fluid should be used in street cars and not for track.

If you are just topping off then it would seem low risk. If you are doing a full flush why not spend a few dollars to be sure. If you flush your system every two years it seems to me that you don't want to use stuff that is more than two years old.

Isn't the MC reservoir vented?

that makes sense.. if you're going to all the trouble to flush the brakes... why not just use new fluid... but these cans of fluid build up in the garage and we don't like throwing stuff away.. I need to make a recycling run... I have all sorts of containers on the side of the house. Brake fluid, trans oil, coolant. My garbage company will take engine oil but that's it.

cgarr,
I was thinking the same thing.... vented = the air on top of the fluid has moisture right?

On more thing: If the container is full or nearly full, then the amount of air containing moisture is minimal. I wouldn't keep half full containers around too long.

From your description it would sound like you need to discard the brake fluid and use new brake fluid. Also, if the car is being tracked, where high brake temps are likely, I have yet to see anyone use opened brake fluid. The general rule of when in doubt use fresh fluids seems timely as well.

That being said, since there have been no references to source information/data on such (mine included) why not ask the source? Consider going to ATE North Americas homepage www.ate-na.com for contact info. Ask them what the shelf life of their fluid is after being opened and any data they have to support their claim.

Regards,

Carlton

Brake fluid is hygroscopic and takes up moisture very quickly. The moisture seems to settle in the brake caliper where rust will form over time and create a major problem. No one can really determine shelf life without measuring humidity and storage conditions. I would feel better storing brake fluid in a garage in Scottsdale, Arizona then here in Atlanta, Georgia! :(

Porsche brakes are legendary, we all drive our cars harder then others and depend heavily on a sound braking system. Bleeding 911 brakes, at least on an older 911 (1973.5T) is quite easy, so I try and bleed the system at least once a year if not more!

With that, using a can of Racing Blue fluid is well worth the peace of mind and price to ensure my brakes hydraulics are in top shape.

Bob
73.5T, in Sepia :cool:

I write on the outside of a brake fluid container the date I open it. Won't use one more than 3 months old after its been opened.

I agree re the air space, but note also that the closure, once breached can never be perfect again. Also, he has a big air space in the can.

Do what Bill said - how many pennies are we talking about here??

Also, discard does not mean toss in trash. Brake fluid is hazardous waste. Take it to an auto parts store, or Quikie Lube - they'll put in the right haz. waste recycle can for you. Or take it to your county or city transfer station for the same thing.

Can't one vacumm seal it to keep moisture out?

yes, if you trust the seal.

We've had all sorts of problems with Oxygen migration into or out of supposed perfect tubing runs while doing weird things to baby birds and mammals. We finally tore out everything and went with stainless steel tubing for most of it. Could have been the cheap labor (grad. students) not the material. Also, oxygen is not water vapor, but ...

KIS and toss the brake fluid for recycling.

not sure if we need to go on and on with this... I don't advocate using old bf. ... but
I assume open for 5 mins. seal.. this means no more moisture goes in the fluid because the cap is sealed closed. So I think what we are comparing is:
1 - new un opened brake fluid
to
2 - brake fluid that has been opened and then quickly closed/resealed. This causes x grains of water vapor to get trapped in the can.. this then gets absorbed into the bf. From what I read Dot 3,4 fluid is designed to put the water in suspension and evenly distributed. It does not go somewhere and pool as a rule. Dot 5 does tend to pool easier.

if we don't think putting the cap back on tight seals the can then of course all bets are off..

I use the blue (old can) for flushing - I'll let the MC container get down low (pump the existing out) - then pump some blue through there - let a couple of pumps in each caliper. Then flush normally for my DE prep. Then I know that when I have worked the "blue" through the system that I'm working of fresh fluid.

In Florida - I tend to bleed the brakes closer and closer to my drive time - my mechanic recommended no more than 48 hours before an event because of so much inherient moisture in the air.

True Randy, but why dispose if it's still useable? On a partially filled can, insert marbles or ball bearings to displace the air, then seal the can and put it in a HD zip lock bag. Why dump good BF if it costs $75/liter or even $10/liter?

People in the US waste and use up more resources than anywhere in the world.

Sherwood

I do something similar. I use the "old" brake fluid for brake bleeding after I have broken the brake lines. Then use the pristine unopened can of fluid to do the final flush and end up with all new fluid. Why use good fluid to perform a brake bleeding? I know, I'm a cheap bastiche.

That should help a lot Sherwood, and I do appreciate the thrust of your comment.

I will bet a lot more is wasted by people changing their fluid every few months in LA ("before every D.E.") than by this however...

What about an unopened can
 

I have an unopened (still sealed) can in my garage of ATE blue, I would guess it is close to five years old. Is it still good?