Brake Fluid

elljay

I've always thought that once you've opened a can of brake fluid that if you only use some of it that the rest has to be thrown out. However this seems so wasteful. I bought a 500ml can but even though my brake fluid was on the low limit, filling the reservoir full didn't use half that much. Do I really now have to throw the rest out and if so, is it possible to buy smaller quantities? I haven't seen them,.

Thanks

Liz

enfield_freddy

it should be ok if stored in its SEALED container for a reasonable period , much the same as it (the other half) is now stored in your fluid reservoir

facade

Check your brake pads, if they are fine, get the braking system checked for leaks.

Modern cars are "designed" so that the drop in fluid level puts on the "check brakes" light, if you are at minimum then either there is a leak, or the pads are worn out.

It is also possible that you have a "modern" car with the clutch cylinder entirely inside the gearbox, fed from the same reservoir, so this may be leaking instead.

elljay

Don't know how 'modern' it is, around 15 years old and over 200k miles. Does that count as modern?

Yes the light had come on but now I've topped up the fluid the light is off.

It was MOT'd about 2 months ago, no brake related advisories.

I'll keep the remainder of the bottle then, glad for that advice. Thanks.

Iceweasel

elljay wrote: »

Don't know how 'modern' it is, around 15 years old and over 200k miles. Does that count as modern?

Yes the light had come on but now I've topped up the fluid the light is off.

It was MOT'd about 2 months ago, no brake related advisories.

I'll keep the remainder of the bottle then, glad for that advice. Thanks.

The MOT doesn't report at all on the state of the brake pads - only if the brakes don't reach the woefully poor level of efficiency needed to pass.

Clapped out brakes with virtually no pad left will easily pass the MOT.

You need to check how much wear is left on the pads.

The level of fluid goes down as the pads wear - replacing the pads puts the level back up.

If you need to top up for any other reason, then you have a leak.

facade

I didn't explain very well.
In The Olden Days, (when cars used to have inscriptions like Rover on the back, and seats made from dead cows) cars used to have pad wear sensors built into the brake pads, to put a light on if they wore right down.
Then cost-cutting started, and they went down to one sensor, and hope they all wear down together, they they fitted a soft rivet that squealed when it touched the disc at the limit of wear.

Then someone realised that they could just wait for the fluid to drop down as the pads wear, and put on the low fluid light, saving even more money!

This relies on owners either topping up the fluid and keeping a close check on the pads, or never lifting the bonnet, so the system works as "designed". Topping up and not checking can result in pads wearing right out, and damaging the discs (the brakes don't work too well either), then when the new pads are fitted, the level goes back up, and the reservoir will overflow, damaging the paint near the reservoir.

Iceweasel

Spot on there, facade. :beer:

Some of us still sit on dead cows though.

facade

The nearest the "half leather" seats in my Nissan have been to a cow is when I put a Macky-D meal on the passenger seat once.

"Modern" cars are anything made since 1980

I still miss my old Rover P6 (that had a sensor on each calliper), but I'd have hoovered it off the drive years ago.

Strider590

The less air in the container, the longer it will last.

Oblivion

It's a long time since I did my own car mechanics, but if I remember correctly brake fluid is Hygroscopic meaning it attracts and holds water molecules which will eventually seriously impact on its effectiveness.

As has been said, the best way to store any remainder is with the lid tight shut to keep out any damp.

Strider590

Oblivion wrote: »

It's a long time since I did my own car mechanics, but if I remember correctly brake fluid is Hygroscopic meaning it attracts and holds water molecules which will eventually seriously impact on its effectiveness.

As has been said, the best way to store any remainder is with the lid tight shut to keep out any damp.

This is pretty much right, if your concerned the seal around the lid isn't any good, then pop the bottle inside an airtight container along with some fresh silica gel packs.

I keep moisture sensitive items, like silicone sealant and super glue in just such a way, because I buy large containers/bottles/tubes instead of being ripped off for the tiny ones, but these can go off when left exposed to normal humidity levels for several months.
Silica gel packs reduce the humidity to near 10%, low enough to make such things last as long as they would have before opening.

I then just pop the silica gel packs in the oven once every few months at 140C to renew them.

Nice little money saving tip that one! A LOT of stuff would last much longer in humidity controlled storage....... wet razor blades for example, preventing rust on the shaving edge and making them last days/weeks longer :cool: