Brake Fluid

[Karl Bird]

Just a quick one. What's the shelf life of brake fluid once opened ?

[CptBlack]

I was told a couple of years if kept properly - same as the fluid used in the bike

[ms51ves3]

The garage I used to work at threw it out after a week if the foil had been broken. Free brake fluid for me then

[Howling TerrorOutOfOffice]

Most manuals say change the fluid every 12/18mnths.
So thats fluid in a sealed system.

Its hydroscopic, so if opened and unused will start absorbing water from the atmosphere. Some places are more humid than others so that will make a difference.

If i haven't used mine after 3mnths i bin it.

In short. Don't know.

Pat
____________________
Diabolical homemade music Bandcamp and Soundcloud
Singer songwriter, Artist and allround good bloke Listen to Andrew Susan Johnston here
The Harry Turner Project

[Karl Bird]

Thanks for the replies. The fluid i've just used after changing the piston seals is about 3 months old with the seal broken and has been stored in a damp shed. I'm thinking it may be why I can't get a very firm lever. I've just ordered a Hel braided line and will use new fluid when I fit them.

[CptBlack]

As far as I'm aware, fluid that has absorbed water shouldn't make any difference to braking as it is incompressible like oil/brake fluid. It just rusts the insides of the reservoir/piston etc.
Happy to be told otherwise though.

If you're spongy, maybe trying bleeding again

[Kickstart]

Hi

Not sure on how long it can be kept open, but I wouldn't want to trust it after a few months. 3 months doesn't sound wrong.

But water itself isn't compressible beyond a tiny amount (and brake fluid is also compressible by a tiny amount), so that shouldn't have any real effect on how firm the lever is when stationary. Problem with water is that it boils at a low temperature compared to brake fluid and braking generates heat. When it boils it turns to steam which can be compressed.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Walloper]

You need to get ALL the air out of the system.
You must still have air in it. The master cylinder only displaces a tiny amount of fluid (This provides a pressure multiplication force x area)

https://en.wikipedia.org/wiki/Blaise_Pascal

So you need to pump and pump and pump and pump and pu..... etc.

It may mean un-bolting the caliper and holding each one above the master cylinder as you bleed. This allows the air bubble to rise towards the bleeder valve/nipple

Or....

Try a brake bleeding tool.

I had excellent success first time with a Gunson Pressurising tool.
Halfrauds do it.

https://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_204645_langId_-1_categoryId_165469

Some critique on here about introducing 'compressed air' to the fluid being pumped into a brake system using this tool.

Not really a problem as what was maybe being refered to was dissolved air in the fluid.
But even when pressurised to 30psi and the pressure released there was never any visible indication of gas bubbles in the fluid.
The bike was a Triumph Sprint and a pure cnut to bleed.
This tool solved it.

Those Miti Vacuum pump tools are shyte. Do not pull any fluid through.
I saw them in a Nude Book as part of an 'enhancement device' and promptly unloaded mine to an unsuspecting mate.
____________________
W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair

[Kickstart]