How long do you trust open brake fluid to still be good ?

[MikeF2316]

Funny, Most all American cars did it for decades...

Tommy

Yes I'm thinking of that GM master cylinder with the huge cap that was held on with a spring that seemed to be on everything that they made in the 70s and 80s. That "cap" was the whole top surface of the reservoir, so a bladder on that could be effective. On European cars, the 2" cap that only was on one of the reservoirs a bladder would be just about impossible to design.

 

[SALIV8]

Brake fluid sits in your master cylinder reservoir that has a small vent hole in its cap. For years.
Assuming a sealed cap is on the stuff on your shelf, you can use it until it's gone.

Modern brake master cylinders have vent holes in them?

 

[Tonyuk]

Modern brake master cylinders have vent holes in them?

The cap doesn't form a perfect seal around the fluid to prevent a vacuum forming in the system. This is why there's a nice steady flow when you crack a bleeder open as fluid comes out. Crimp off your rubber brake hose and crack the bleeder, you'll see the difference.

 

[ZipSnafu]

With the cost of brake fluid being so cheap... why bother. But in a pinch I would use an opened container of brake fluid for a couple of months before I would really call it trash.

 

[Lotek]

Here is what the manufacturer says;http://www.epicbleedsolutions.com/resources/faq/shelf-life-of-dot-mineral-oil-brake-fluid/

Shhhh, you are talking sense here...why ask the manufacturer?

 

[ken w.]

A pint of brake fluid is @ $ 3.00 in my area. I only buy pints. If you put calipers (2) on most cars you don't usually need more than a pint to bleed the system. For $ 3.00 I'll buy a new bottle or 2 than save a 1/4 of a bottle. My garage used to have open brake fluid bottles all over the place because I used to save them. I'm over that. And how many of you guys properly dispose of your brake fluid ? I dump mine in my used oil drain , not in my trash.

 

[rlitman]

Shhhh, you are talking sense here...why ask the manufacturer?

Because the manufacturer's best interest is in selling you more of their product.

Expiration dates are the biggest scam pulled on the world since "lather rinse repeat".

 

[DadsTools]

"Peace of Mind" has an intrinsic value that's difficult to assign a price tag to it but nonetheless very real. We're talking brakes here, and that's high on the confidence scale.

Our motto here:

In case of doubt, throw it out.

 

[Montyx5]

The cap doesn't form a perfect seal around the fluid to prevent a vacuum forming in the system. This is why there's a nice steady flow when you crack a bleeder open as fluid comes out. Crimp off your rubber brake hose and crack the bleeder, you'll see the difference.

If there is a broken seal between the fluid and atmosphere, then there is a component failure. If fluid flows freely when a bleeder is cracked open, there is a problem. You may or may not get a very small amount initially when opening a bleeder on a properly operating system of modern vehicles. After that there should be no measurable flow except for any that flows due to air entering the bleeder replacing any fluid that leaves.

 

[Falcon67]

It's cheap - buy what you intend to use then toss. If you expect to use more, keep smaller sealed bottles on the shelf. Don't buy a big bottle with intent of keeping it around 2-3 years.
Unless you are a repair shop or maintaining race vehicles it just gets contaminated. I just don't keep open brake fluid. Not saving anything IMHO.

 

[Richard Cranium]

I buy it in the smallest container, and then throw away what is left over. Don't store any opened up.

 

[lionsgarage]

What he said, all depends on the humidity where one resides.
Here in the PNW it's gone in a month w/o a lid, a few months with a lid.

 

[Dragfluid]

As long as the container is capped tightly, keep it it until it's all used.

Yes, it's fine.



Lutefisk

 

[capww8]

I'm firmly in the 'buy small bottles and pitch them after they're opened' camp.