When to change brake fluid?

System

fred246 wrote: »

The main driver is simply profit for garages. If it isn't changed you won't have any problems.

Other than you know your brakes not working as well as they should do in prolonged braking and your brake pipes corroding from the inside out.

If they charge you and then don't do anything you won't be able to prove it.

Given they have to undo the bleed nipples to change it and in most cases the existing fluid will be brown whereas the new is almost clear you most certainly can.

I doubt many garages would truly flush out all your brake pipes.

Given that they use a tool that fits pipes on every bleed nipple then sucks the fresh fluid through from the master cylinder it is impossible not to.

Richard53

Tarambor wrote: »

and your brake pipes corroding from the inside out.

To be fair, it would take a long time for steel brake pipes to rust through (although I wouldn't want to be a passenger when they do). Cunifer should last almost forever.


However, most of the older cars and bikes I have owned have had problems with the brakes at some point, which have almost always been due to internal corrosion - rusty pistons leading to faulty seals etc. There is no way moisture can get inside a caliper unless it is in the fluid, so I would attribute 90% of those problems to old fluid.


Calipers are expensive, and brake fluid is (relatively) cheap and easy to change.

Car_54

Richard53 wrote: »

To be fair, it would take a long time for steel brake pipes to rust through (although I wouldn't want to be a passenger when they do).

Particularly so since rust (if I remember my schoolboy chemistry) needs oxygen as well as water. I'd have thought that oxygen (air) in the system would be noticeable long before rust was a problem.

Also, the quantities of water within the pipes would be much less than on the outside, in our climate.

fred246

It's amazing how the pipes let water and oxygen in but the brake fluid doesn't get out.

AdrianC

Car_54 wrote: »

Particularly so since rust (if I remember my schoolboy chemistry) needs oxygen as well as water. I'd have thought that oxygen (air) in the system would be noticeable long before rust was a problem.

Also, the quantities of water within the pipes would be much less than on the outside, in our climate.

The outside of the pipe is usually plastic-coated. The inside isn't.

And the inside of the cylinders isn't, either, and they're usually the first thing to need replacing because of corrosion - the rough surface causes the seals to fail, and they leak.

AdrianC

fred246 wrote: »

It's amazing how the pipes let water and oxygen in but the brake fluid doesn't get out.

The water (from atmospheric humidity) gets in through the vent hole in the reservoir cap, which isn't hermetically sealed, because the level raises and lowers as pads wear and get replaced.

As for the oxygen - remind me what water's made of? There's also oxygen within Ethylene Glycol - (CH2OH)2 - which is the base of DOT brake fluid.

Jackmydad

Change it regularly. Safe over cheap every time.
Can't afford to have it done? Then get a Gunson's Eezibleed and DIY. (You can do it without but it makes it dead simple)
Can't afford to DIY?
Then you can't afford to run a car.

EdGasketTheSecond

I've never changed brake fluid for the sake of it in over 40 years of car ownership/driving; never had a problem.

Iceweasel

EdGasketTheSecond wrote: »

I've never changed brake fluid for the sake of it in over 40 years of car ownership/driving; never had a problem.

Can I have the winning lottery numbers for next week please?

House_Martin

EdGasketTheSecond wrote: »

I've never changed brake fluid for the sake of it in over 40 years of car ownership/driving; never had a problem.

Me too, but I ve bled hundreds of brake systems and had plenty of seized bleed nipples in brake calipers and rear pistons sheer off. Then a £50 fluid change could turn into the cost of a new front caliper.
I would` nt trust a garage to diligently go round the 4 bleed nipples to do the job properly and I would expect it would cost more than £50 anyway. The fluid cost will be a tenner
.Be aware with older cars, the weak bleed nipples will shear off easily. They take the brunt of the weather and salt for years. Garages will simply bill for new pistons or calipers if this happens and pass on the costs.
2 years for a brake fluid change is simply health and safety nonsense .Brake fluid never contacts the outside air anyway to absorb water