Brake Fluid Flush

Given that the Toyota/Lexus hybrid brakes typically last over 100k miles, comparison to conventional brakes seems inappropriate. I think we're going to need some testing like we have for transmission fluid. Meantime, I'm changing the transmission fluid early, and leaving the brake fluid alone until the pads need replacing.

 

I guess I understand that bad transmission fluid damages the electric motor windings. One of the reports of transmission failure on a Gen1 was resolved by changing the transmission fluid. Seems to be a reasonably well established fact that the fluid goes bad and damages things.

With brake fluid, the degradation seems to be water dilution and a decrease in the boiling point of the fluid. So failure would be the brakes not working when they get too hot. The major problem that has been reported with Prius brakes is that they rust due to lack of use. Some people have to actively do some hard stops occasionally to wear off the rust. Regenerative braking prevents most use of the mechanical brakes on a conservatively driven car. Basically, the people who boil brake fluid are not likely to be found driving a Prius.

So I'm interested in seeing any test results, but it's more of an intellectual curiosity than any expectation of problems. In any case, someone else is going to demonstrate the problems long before I reach that point.

As for the CT200h, it seems to demonstrate that different market conditions drive different service recommendations. Oil change recommendations differ between Europe, Canada, and the US for the exact same car. If engineering completely controlled the recommendations, then we wouldn't see such differences. I'd rather follow engineering considerations than whatever the legal/political/competitive factors that drive Toyota.

 

Don't know if this is in all parts of Europe, but here in Slovenia, they make brake fluid change every 30.000 km or 2 years.

 

Someone here recently made this suggestion: occasionally when stopping the car, shift to Neutral (which disables regenerative braking). This will employ the regular brakes for the full stopping effort.

 

The most common reason for water contamination in brake fluid in modern cars is people taking the fluid container top off to check the fluid level. The top should only be removed to top the fluid up if it is below the low level line, and if so the system should be checked for leaks. As disk pads wear the fluid level will go down but the fluid should not be topped up because this runs the risk of dirt and moisture entering the system, also when disk pads are replaced the fluid will overflow or at worst split the fluid container if the top is left on. The top contains a bellows mechanism (witch unlike old cars that just had a breather hole) seals the system from outside air and water vapour.
The Prius is very gentle on it's hydraulic brakes they seldom get even warm and pad life is often five or more times that of conventional cars and while I see know harm in changing fluid every two years I believe five years or 100,000 miles to be a realistic period.

 

Color alone is not a good indicator of condition of oil. UOA will give you a more refined answer.

DBCassidy

 

================================================
The VIM is the connector ???
Just to be safe I'll get 4 cans of Genuine Toyota DOT3.

Thank you for your help.

 

Can you post links to the equipment you used to do the job? Might be something I acquire for the tool kit.

 

A good video posted by NutzAboutBolts is now available here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

for bleeding, without the need for Techstream. No special equipment needed, two-man method.

 

They do use a vacuum tool to bleed the brakes, and that's a special tool, although not too expensive.

 

He says something tho, about it not being a necessity. Apart from the initial emptying of the reservoir, which he mentions could be done with hand pump (or large syringe, baster, what have you), the bleeding process is pressure driven, driven by the foot on the brake pedal.

 

100K maint - 1

It is a very old thread but I just to point out that brake fluid in hybrid virtually has mild wear and last really long. 10 years interval is more than enough.

 

Maybe one of the best takeaways from that post is that there are test strips, too, so one doesn't have to guess, or make assumptions about whether one's own driving conditions, climate, etc., are going to result in the same longevity for the fluid.

The fact that hobbit's fluid was in such good condition at 100k miles was established by the test strip; the explanation of why (easier life in a hybrid) is plausible, but not something he specifically set out to test.

 

To the extent that brake fluid degradation is due to atmospheric moisture slowly permeating through hoses and seals into the fluid, I don't see why fluid would last any longer in a hybrid.

 

Honda says replace tri-yearly, regardless of miles.

 

If the explanation isn't something hybrid-specific, then it may just be that there is enormous variance in the longevity between cars in different climates or driving conditions. Which, again, points up how handy it is to have simple tests available.

 

Is the brake fluid water contam more or less homogenized, ie would fluid at caliper be sim to at reservoir? At caliper is likely to have more crud though.