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Did my friendly Subaru dealer get over on us?

I just did a search on changing brake fluid. Would link to the site, but I do not know how. At any rate, it says there’s no mention in the service manual of changing brake fluid on GM and Ford vehicles. Maybe that’s where the urban legend comes from. Most of my vehicles have been domestic. I guess that’s why 30k seems early. I didn’t see Toyota’s recommendations listed.

The site does advise to change it, though. “why change brake fluid”. Hopefully that isn’t considered spam. Didn’t notice if they were trying to sell anything.

looks like Toyota does not specify brake fluid change… EVER (???)

my DIY maintenance was always around Subaru / Nissan / Mazda, these require change explicitly, will not tell about other brands

Lol, well there ya go. No wonder 30k seems early to me! It’s odd how different manufacturers recommend different service intervals as far as oil changes, brake fluid changes, etc. I know engines and components vary, but brake systems seem fairly similar across brands.

unless Toyota possesses some secret knowledge…

in general, I prefer spending 20 minutes replacing fluid every other year than to spend more time/money dealing with stuck calipers

Agreed. Thanks for the pdf. It reminded me I forgot to get an air filter when I picked up an oil filter earlier today. Dang it.

What’s your method on changing brake fluid? Gravity bleed, do you have a vacuum pump or what?

I’ll be honest, I don’t change it, but probably should. 94k on the Toyota, no issues. 150k on the Buick, no issues. 200k on a past Dodge Ram - failed master cylinder. 208k on a past Toyota, no issues. Prior to those, the vehicles I’ve owned were so old when I got them, I wound up replacing most of the brake components anyway at one time or another.

But yes, if you’ve got a fairly easy one man way of doing it, I’m in. I do think it’s a good idea. Domestics and Toyota manuals have blinded me lol.

Branick diaphragm brake bleeder

I’m not a fan of vacuum bleeding. I’ve had success with gravity bleeding in a pinch, but you’d better have plenty of time on your hands

probably it’s not the best, but for one-man-way, I’m doing:

  • suck as much fluid as I can from the upper tank, replace with new
  • attach an aquarium tube to the bleeder
  • make a bend up&down to make sure some no-air fluid space would form
  • dump into a disposable water bottle or any container
  • get some petroleum jelly on bleeder threads to prevent air from sucking in
  • open bleeder, let fluid to fill the tube for few inches
  • start pumping pedal in “medium speed down / sloooow up” manner
  • measure how much fluid gets replaced with 10 pedal strokes, refill regularly
  • once you establish how many pedal strokes it takes before level drops to MIN, work starts going faster
  • if fluid is old, it is clearly visible when new one arrives at bleeder by observing the fluid in tube

the order of what wheel to bleed first and what last is always debated :slight_smile:

I use “start from the farest from the master brake cylinder, work to closest” order

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No, Toyota possesses, or at least did for awhile, idiot marketing agents. They ran a big ad campaign awhile back that showed a guy welding his hood shut because you never needed to open it, as the car required no maintenance. It was entirely BS, of course, and anyone who acted on that message would destroy their engine, but the aura of “having to do maintenance is bad and so our cars don’t require much if any” has remained.

Just because the marketing department tells you you don’t have to change fluids doesn’t mean it’s true. :wink:


It may be more of an urban myth that brake fluid needs to be changed at all. In the old days brake fluid started turning dark after 1 year and by year 3 it was black. Then sludge would appear at the bottom of the master cylinder reservoir and by then everything that could start leaking did. So once a year or two flushing saved lots of money and made the car safer. I’d love it if a chemical engineer out there in Car Talk Land weighed in. Until then I’m skeptical that pristine brake fluid is bad. After engine oil had improved to the point that manufacturers said it was good for 10K under non-severe use there’s still people changing it every 3 to 5K.

It’s hygroscopic. That means it absorbs water. Water in the brake lines is bad for a number of reasons. Even if it looks great, it should be changed every 3 years or so to get rid of the absorbed water.


No it is NOT an urban myth. Brake fluid is Hygroscopic (absorbs water). You need to flush it out periodically. 30k may be overkill, but it does need to be done. I do mine about every 50k miles. If you’re somewhat mechanically it’s a simple job (just time consuming).


That’s what I’ve been hearing for a long time. What hasn’t been explained is how that happens in a sealed system.

It’s not that sealed.


It’s sealed enough to keep brake fluid from leaking out, but it’s not completely air tight. Air will get in over time, and that air will bring water vapor in with it. Even the International Space Station leaks a small amount of air, and it goes without saying that the seals on that thing are a lot better than the plastic cap on your MC reservoir.


On the bright side, your 2+ years of maintenance have only cost about $545. That does not sound worse than what I have seen on my cars that hit 30K. Hope you can work it out and find a happy resolution.

Air replaces the brake fluid in the reservoir as its level drops through the caliper displacement that happens as the pads wear. The relatively large surface area of the reservoir fluid then absorbs some of the air. The inner diameter of a brake line is small, perhaps about 3/16", meaning it takes little air to allow problems.

Beyond that, and perhaps more of a reason than water absorption, is that your brake components including the Master Cylinder, the ABS modulator, the caliper, their pistons, and the flex lines all contain rubber O-rings and, in the case of the flex lines, liners. Elastomers break down and this contaminates the brake fluid.

Brake fluid should be flushed out and replaced periodically. I generally do mine a bit at a time when I do brakes and occasionally the whole system. It isn’t expensive and it protects perhaps the most critical safety system in the entire car.

Remember: an engine that won’t start in the morning can ruin your entire day, but a brake system that won’t stop your car when you hit the pedal can ruin your entire life.


To add to this, you push the pedal, level in reservoir slightly drops, you release it, it gets back.
This motion is relatively small, but combined with air vent in the cap, it lets air (and moisture) to get in and get trapped in a hydroscopic fluid.

Similar cycle happens with natural temperature and air pressure changes.

In Subarus I had before they used to have a special rubber membrane in the cap which was flexing with this up/down motion, so the system was more airtight than I see in my current Nissans.

Air replaces the brake fluid as the level drops in the reservoir? I’d love to know where that air comes from considering the system develops 1,200 psi when you step on the brake and no fluid gets passed the seals. It’s hard to believe that air gets passed those seals when the fluid level drops. The lid of the master cylinder has a neoprene diaphragm that expands downwards as the fluid level drops.

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On the upside, having that stuff done – along with the general inspection they do at the same time – will make your car perform better and last longer. The downside is, it was a little pricey. Does the paperwork you signed before they started the work show an estimated price? If it does, then you don’t have much right to complain. No estimate, then show that to the servicing manager and remind them that they should provide a clear price estimate to you whenever servicing your car.

Many car owners prefer to use an inde shop for routine service like this once the warranty services expire. Find an inde shop where they offer a service that prioritizes what needs to be done now and what can be deferred. Plus an inde shop will be a little less expensive overall. You don’t need to pay a dealership shop to install a cabin air filter.

Ideally the dealership would have reminded you that the service was no longer covered by the warranty, but you can’t expect the service writer to remind you of everything about the warranty. It’s always best to show them the warranty and ask them first what’s covered and what isn’t.

The pressure is developed after the reservoir has been sealed off by the piston. 5 seconds of looking at a master cylinder diagram would clear all this up for you:

As the pistons travel to the left, the piston seal passes the inlet from the reservoir, at which point all the pressure is going into the lines and not into the reservoir.