Kia says to flush brake fluid every 4 years?

[4WD]

My Jeep just reached 4 years with only 32K …
Have changed all fluids but power steering and brakes …
Seems mileage should factor in some …

 

[4WD]

How about getting a test pen and change brake fluid when it's deteriorating? Keep out of the doubt and sleep tight.

Maybe I’m wrong - but always see brake fluid as having the most oxidation potential at the brakes - and least at the reservoir - yet some only change it at the reservoir …

 

[4WD]

If only there were some way to tell. ;-)

View attachment 232067

Is that representative of what’s at the calipers?

 

[CarlB]

Is that representative of what’s at the calipers?

The fluid mixes, but the fluid closest to the caliper absorbs more moisture due to the heat and thermal cycling.

Ignoring is an option, but water boils at a much lower point than brake fluid. It's ultimately a personal choice.

 

[kschachn]

Yeah my VW says every two years. I have been using the Bosch multi-DOT stuff which seems fine.

 

[Astro14]

The fluid mixes, but the fluid closest to the caliper absorbs more moisture due to the heat and thermal cycling.

Ignoring is an option, but water boils at a much lower point than brake fluid. It's ultimately a personal choice.

How would the fluid at the caliper absorb more moisture? Sure, it gets hot and cools, but the caliper is sealed, as are the lines and hoses. Water won’t permeate steel, aluminum, or copper. There isn’t enough permeability in the lines or caliper seals to allow contamination.

The sources of contamination in fluid are moisture at the reservoir (which is vented to the atmosphere) and the bit of rubber degradation in the seals of calipers and linings of hoses.

Moisture gets distributed through the brake system by thermal cycles, which move fluid in/out of the reservoir, as well as normal permeation in the fluid itself. But the source of contamination is less important than the fact that it exists. That it can degrade fluid boiling point and cause corrosion in expensive components.

Flushing the fluid completely removes all of that contamination. Flushing, and the resultant clean fluid, assures best braking performance under extreme conditions, like high speed, stopping a trailer, or mountain driving and help prolong the life of brake components.

 

[CarlB]

How would the fluid at the caliper absorb more moisture? Sure, it gets hot and cools, but the caliper is sealed, as are the lines and hoses. Water won’t permeate steel, aluminum, or copper. There isn’t enough permeability in the lines or caliper seals to allow contamination.

The sources of contamination in fluid are moisture at the reservoir (which is vented to the atmosphere) and the bit of rubber degradation in the seals of calipers and linings of hoses.

Moisture gets distributed through the brake system by thermal cycles, which move fluid in/out of the reservoir, as well as normal permeation in the fluid itself. But the source of contamination is less important than the fact that it exists. That it can degrade fluid boiling point and cause corrosion in expensive components.

Flushing the fluid completely removes all of that contamination. Flushing, and the resultant clean fluid, assures best braking performance under extreme conditions, like high speed, stopping a trailer, or mountain driving and help prolong the life of brake components.

That fluid gets hot and rises.

 

[Marcozi]

I change my car's BF every 2 years, and the week before I take him to the track.

 

[kschachn]

That fluid gets hot and rises.

And then what?

 

[ARCOgraphite]

Since when is the reservoir vented to the atmosphere? There is a diaphragm over the fluid, the vent is above the bladder.

 

[Astro14]

That fluid gets hot and rises.

Yes, it does get hot. It expands.

But that doesn’t mean that it is sucking moisture in through the calipers.

It is mixing as a result of expansion and contraction.

But the moisture is present at the reservoir because of the cap vent, that is the point of absorption.

 

[Astro14]

Since when is the reservoir vented to the atmosphere? There is a diaphragm over the fluid, the vent is above the bladder.

And how does the reservoir account for expansion and contraction for thermal cycling of the fluid? How does the reservoir let the brake fluid level decrease over time?

It’s not a vacuum tight seal.

Fluid is kept in, but air can move in and out, or you would never have the fluid level go down over time.

 

[slacktide_bitog]

I disagree about Supertech. It's more vulnerable than better fluids.

Used it in a Toyota for about 2-3 years after flushing OEM. Needless to say, coming out a vibrant green is not a good sign. Not when the OEM fluid was only lightly discolored over a much longer period interval.

Castrol's DOT4 is also a better fluid, being low moisture accumulation for British cars with systems apparently open vented to the atmosphere.

I actually was going to suggest Castrol, but I haven't seen the Castrol brake fluid available anywhere for at least a few years. Even Amazon doesn't carry it


What did you replace the Supertech with? OEM Toyota? Castrol? Something else? And did the green come back?

 

[ARCOgraphite]

And how does the reservoir account for expansion and contraction for thermal cycling of the fluid? How does the reservoir let the brake fluid level decrease over time?

It’s not a vacuum tight seal.

Fluid is kept in, but air can move in and out, or you would never have the fluid level go down over time.

The diaphragm is accordioned and follows the level down as the pads wear, The air is above the diaphragm.

 

[CarlB]

Yes, it does get hot. It expands.

But that doesn’t mean that it is sucking moisture in through the calipers.

It is mixing as a result of expansion and contraction.

But the moisture is present at the reservoir because of the cap vent, that is the point of absorption.

I never said it did. The caliper is the heat source, that fluid gets cooked.

 

[CarlB]

And how does the reservoir account for expansion and contraction for thermal cycling of the fluid? How does the reservoir let the brake fluid level decrease over time?

It’s not a vacuum tight seal.

Fluid is kept in, but air can move in and out, or you would never have the fluid level go down over time.

The fluid level decreases mostly from pad wear, since the caliper piston sits closer to the rotor lowering the master cylinder level. Often why when people get a brake fluid light on their dashboard it isn't advisable to just top-off and move along, but actually inspect pad depth.

 

[Astro14]

The fluid level decreases mostly from pad wear, since the caliper piston sits closer to the rotor lowering the master cylinder level. Often why when people get a brake fluid light on their dashboard it isn't advisable to just top-off and move along, but actually inspect pad depth.

I know why it decreases, but if the reservoir were sealed, as some suggest, it would not decrease. Air is not getting into the system from the calipers, or the piping, or even the hoses.

Air gets in to the brake master cylinder reservoir, period.

 

[Astro14]

The diaphragm is accordioned and follows the level down as the pads wear, The air is above the diaphragm.

There is no diaphragm on any of the ATE equipped cars I own. There is a seal. It’s part of the screw-on cap. It is flexible. It allows air to enter.

The Tundra reservoir cap is just that - a cap. No diaphragm. Just a cap covering the reservoir.

I haven’t seen a diaphragm in the cap since I sold the 1977 Oldsmobile, and that was a diaphragm in a heavy metal cap, that was held on with a bail clip. I think we have moved on since those days.

 

[VersatileGuy]

I actually was going to suggest Castrol, but I haven't seen the Castrol brake fluid available anywhere for at least a few years. Even Amazon doesn't carry it


What did you replace the Supertech with? OEM Toyota? Castrol? Something else? And did the green come back?

I replaced it with Castrol at the time.

I had brake hose issue that cause me to lose most of the castrol. Maybe there's some left in the rear brake lines that still have some color, but it has been contaminated with new Supertech because the brake pipes decide to take leak after being disturbed(and me messing up the removal a bit).

So the only sure comparison was with Toyota OEM. The Toyota was not clear, but it wasn't heavy green either. A modest yellow-ish brown but the car was bought in 2007 and the replacement was in the mid-to-late 2010s. I guess the amine and polyalkene glycol ether might take on water, but be more resilient.

Castrol uses an amine too, different from Toyota. Toyota's bottle mentions Di-n-butylamine. I recall finding one google site that states it is an anti corrosion chemical. I checked Castrol's MSDS and they have Di-isopropanolamine.

Related to Toyota, Advics sells a brake fluid. Curious about the difference between them and Toyota OEM, I got a vague but not incomprehensible response.

The email.

The formulations of the ADVICS DOT 3 brake fluid and Toyota OEM DOT 3 brake fluid are very similar but they are not the exact same formulation, and I cannot speak to the specific differences as the Toyota fluid formulation is proprietary.

However, I can state that the ADVICS DOT 3 brake fluid formula has been approved by a major Asian OEM brand as well as a major Detroit 3 OEM brand. Also, when benchmarked against other OEM brands, the ADVICS DOT 3 brake fluid outperforms many of the OEM brands.

When researching brake fluid, the two main points to consider are the wet and dry boiling points. Typically, the higher the boiling points for each of these two categories indicate a higher quality fluid.

So I guess if someone is buying one American car brand, they're buying closet "Toyota-influenced brake fluid". My speculative guess for the Detroit automaker is GM because of their past relationship with Toyota. But who knows, maybe the Motorcraft fluid is Advics' sauce.

Given my experience with the Supertech, I can see why OEMs go for something better. Brake fluid is going to be neglected and whatever simpler formulation Supertech has, it might go too fast and then a class action lawsuit can occur. Tubing rusting, calipers seizing, seals failing, loss of braking ability after prolonged use.

Maybe do the BITOG thing and send samples to a lab?

I'm planning to go OEM Toyota because I'm about to install a new brake calilper. At least for an initial session, it's best to replicate factory conditions.

 

[Carmudgeon]

There is no diaphragm on any of the ATE equipped cars I own. There is a seal. It’s part of the screw-on cap. It is flexible. It allows air to enter.

Ate has been consistently using the same basic, threaded coin-edged cap for at least 40 years.

https://www.google.com/search?sca_e...IHS89LlYQtKgLegQIEBAB&biw=1595&bih=1210&dpr=2

Sometimes it's translucent, sometimes it's opaque, sometimes incorporates a level sensor, but it has always been consistent, which is why it's so easy to find bleeder adapters for them, or roll your own.

I've come across ones with a hole clearly punched into the surface, but even on the ones that don't have any obvious vents, it seems evident that the seal isn't designed to do much more than prevent gross spillage or contamination, not necessarily provide an air-tight seal.

No "lifetime" fluids in cars, folks, except for perhaps blinker fluid. That includes brake fluid, and it's puzzling why some feel that it is exempt, especially on a forum inspired by OCD level maintenance.