High temp brake fluid?

[Murray_Calavera]

6 hours ago, Dose Pipe Sutututu said:

Unlike most of us SAU guys, probably flush it once a decade

lol I thought I was bad 

[MBS206]

8 hours ago, Dose Pipe Sutututu said:

The hardcore tracks1ut guys I know would flush their brake fluid every 6 to 12 months depending on the amount of track work they did.

Unlike most of us SAU guys, probably flush it once a decade 🥲

LandCruiser used to get a fluid flush every 12 to 18 months.

 

Only because it was about that often the electric motor on the master for brake assist kept dieing and needing to come off.

[Dose Pipe Sutututu]

55 minutes ago, MBS206 said:

Only because it was about that often the electric motor on the master for brake assist kept dieing and needing to come off

That's not very Toyota of the Toyota!

[joshuaho96]

16 hours ago, Dose Pipe Sutututu said:

That's not very Toyota of the Toyota!

They've had some weird failures on their brake actuators. One of them was because they added some kind of lubricant to the factory fill brake fluid that aftermarket brake fluid didn't have so it would affect the seals. Another was just mysterious, probably internal corrosion or something eating away at Prius brake actuators. Parts alone for those are a few thousand USD so not a cheap fix.

[Predator1]

On 28/02/2025 at 2:23 PM, MBS206 said:

Give the fluid a really good flush, then go do the same track again. Report back too please

Haha thanks. Will do next year as cars in storage now..... 

[Komdotkom]

On 28/02/2025 at 4:30 PM, Predator1 said:

How hard are you tracking it?

 

Reasonably hard, although I haven't run it with the new Endless setup yet. The old brakes were F50's on 335mm rotors and the car did a 1:40.6 at Phillip Island which is a reasonable time, I'm seeing high 600s on the temperature paint. A guy I know ran the Endless fluid at WTAC without issues and he was doing 1:33's I think (Evo) with a 355/332 setup.

I don't get out to the track as much as I'd like but we put the car on the hoist and spanner check every bolt and re-paint mark everything, bleed the brakes, change the fuel, check the coolant system and re-bleed blah blah blah before every event. Motorsport is expensive, RB's are expensive so a couple of hours before an event is time well spent. It's also a net time saving because if you can keep your RB from self destructing it saves you time in the long term!

[Duncan]

A timely blog via AASA (keeping in mind they sell brake fluid of course...)

https://www.msbgarage.com/blog/news-and-blogs/brake-fluid-what-should-i-use/

[MBS206]

Wait, they're claiming UNOPENED fluid has a shelf life of only 18 months?

[GTSBoy]

4 minutes ago, MBS206 said:

Wait, they're claiming UNOPENED fluid has a shelf life of only 18 months?

Yeah, that and throwing away opened, part used, closed back up bottles has got to be bullshit.

Brake fluid sits in not-very-well sealed master cylinder reservoirs for literal years and keeps working (albeit we know we should flush it every couple of years - it actually still works). Anything kept in a bottle in the shed with a tightly capped lid has got to be a million times better than what has been in the car for the same length of time.

[MBS206]

1 minute ago, GTSBoy said:

Yeah, that and throwing away opened, part used, closed back up bottles has got to be bullshit.

Brake fluid sits in not-very-well sealed master cylinder reservoirs for literal years and keeps working (albeit we know we should flush it every couple of years - it actually still works). Anything kept in a bottle in the shed with a tightly capped lid has got to be a million times better than what has been in the car for the same length of time.

I have multiple bottles in a shed that gets hot, and I'm in SEQ, so it's humid.

Maybe we test their theory... Anyone have a system to accurately measure moisture content in oil?

[GTSBoy]

18 minutes ago, MBS206 said:

Maybe we test their theory... Anyone have a system to accurately measure moisture content in oil?

I'm sure there are specific hygrometers for it. But if you can just throw a high enough ranged temp sensor (theromcouple that came with your DMM, for example) into a pot of it on the BBQ, you can see when it boils.

[Duncan]

1 hour ago, MBS206 said:

I have multiple bottles in a shed that gets hot, and I'm in SEQ, so it's humid.

Maybe we test their theory... Anyone have a system to accurately measure moisture content in oil?

Brake Fluid testers are cheap and readily available....eg https://www.supercheapauto.com.au/p/endeavour-brake-fluid-tester-rechargeable/SPO9539349.html

[GTSBoy]

53 minutes ago, Duncan said:

Brake Fluid testers are cheap and readily available....eg https://www.supercheapauto.com.au/p/endeavour-brake-fluid-tester-rechargeable/SPO9539349.html

Hmm. Two terminals. Probably just conductivity. If you knew the shape of the curve, you could probably just do it with a multimeter.

[MBS206]

3 hours ago, GTSBoy said:

Hmm. Two terminals. Probably just conductivity. If you knew the shape of the curve, you could probably just do it with a multimeter.

After a quick read, it's just conductivity testing.

Might grab the DMM at work and do a 4 wire test on some oil for science. I think Sarah's car is due for a fluid change, so capturing a reading from her old fluid, reading from my unopened old bottles, and then I'll grab a brand new bottle. We'll have to see how far it all varies.

And possibly after this weekend I might be able to steal a spot on a hoist in the workshop across from work to even do the brake bleed easily (yeah, I still hate jacking cars and working on the ground, so I do it in style when possible 😛 )

 

I'll get a small jig printed for the probes so we know we're perfectly keeping the probes at the same distance.

 

Using 4 wire should work perfectly, as it's applying a voltage to measure current, and measuring the voltage drop. that's my theory without being a chemical/physics engineer. GTSBoy, any thoughts on how you'd do it with a benchtops DMM?

[GTSBoy]

5 minutes ago, MBS206 said:

Using 4 wire should work perfectly, as it's applying a voltage to measure current, and measuring the voltage drop. that's my theory without being a chemical/physics engineer. GTSBoy, any thoughts on how you'd do it with a benchtops DMM?

Hmm. Tough one. Without knowing where the conductivity value is supposed to sit, it's hard to know whether a standard DMM set to an available ohms setting would be able to measure anything. Ohms being the inverse of what we're talkng about and probably good enough for the girls I go out with.

But if you want to go all hoity toity with a 4 wire rig - go ahead. It can only be more accurate - just in case more accuracy or repeatability turns out to be required.

If you're going to the effort, just go chuck the ohm-mage probes into the car's reservoir and see if you can measure anything at all?

[MBS206]

A random thought I had just before I hit "Submit on this post".
If brake fluid, in a container in my garage that has never been opened goes bad after 18 months, why can I leave it in my car for 24 months in an "unsealed container"...
Secondly, some other digging, and brake fluid manufacturers seem to be saying 5 year shelf life... Me thinks there line on 18 months for an unsealed bottle is pretty much horse shit marketing spin. Kind of like how if you drive a car and don't run a turbo timer your turbo and motor will die horribly...

 

Where I started on this though... Someone (me) started down a bit of a rabbit hole, I don't quite have the proper equipment to do Equilibrium Reflux boiling per the proper test standards.

I did a little digging on YouTube, and this was the first video I found on someone attempting to "just boil it".

This video isn't overly scientific, as we don't have a known reference for his test either. Inaccuracy in his equipment could have him reaching the 460 to 470f boiling point range in reality.

In the video, using a laser temp gun, he claims his Dot3 that's been open in his florida garage for over a year gets to about 420 to 430 fahrenheit (215 to 221c)
Doing some googling, I located an MSDS for that specific oil, and from new, it claims a dry boiling point of 460 to 470f. Unfortunately they don't list a wet boiling point for us to see how far it degraded toward its "wet" point. While watching it I was thinking "I wonder what the flash point is..." turns out its only 480f for that specific brake fluid....

 

As for testing the oil's resistance, I might not be able to accurately do that unfortunately. Resistance level will be quite a LOT higher than my system can read I suspect based on some research. However, I might be able to do it by measuring the current when I apply a specific voltage. I won't have an actual water % value, but I'll have some values I can compare between the multitude of fluids. I'll run some vague calculations later and see if I should be able to read any reliable amount of current. These calcs will be based on some values I've found for other oils, and see how close I'll need my terminals together.
From memory I can get down to 1pA accuracy on the DMM. I don't think my IOT Power Tester has any better resolution.