Brake fluid flush with Techstream

Brake flush unnecessary. In fact the dealers down here don’t do it as many reports of abs failures because of brake flushing.

Prius is very very easy on the brakes and the fluid. Regen works really good. It’s not anything like a regular car.

Yes techstream is the software to use to manipulate the proportioning relays And dot3 fluid is fine.

 

I used Toyota DOT3 fluid (2 pints, for around $7.50 per), when I did our gen 3, maybe 18 months back. With the dealership's price so reasonable, I'd see no reason to mix brands, just in case.

With 3rd gen there is a Repair Manual instruction for doing the brake fluid change without Techstream, includes a chicken dance that puts the car in "invalid mode". And, @NutzAboutBolts has posted a video, doing the procedure. He mixes up the order of bleeding, but it seems to work out. All I can say is it worked out fine, and the brakes were nice and firm.

That said, I haven't found a comparable 2nd gen procedure, for brake fluid change without Techstream, so there's that. Maybe ask the dealership what they would charge, all in?

FWIW, Toyota Canada recommends a brake fluid change, tri-yearly, or 30K miles (IIRC on the latter), for all their vehicles. For about the last 4~5 years, in the maintenance schedule. Also, Honda Canada says tri-yearly, regardless of miles. I guess that presumes regular use at least, not a museum piece.

 

2nd gen brake fluid replacement discussed here, if you haven't found it:

Replacing brake fluid and bleeding brakes on a GEN II Prius without Techstream | PriusChat

It's too bad there's not a cut-and-dried procedure without techstream, but there seem to be some work arounds. Or just get techstream working.

Attached is the brake bleed procedure per the Repair Manual fwiw, presumes you have Techstream:

 

Don't do the brake fluid flush unless there's a specific REPAIR reason to do it. As Ed pointed out, dealers are instructed not to do it because it can contribute to brake actuator failure.

California is easy on the fluid, leave it

 

Two experienced second gen voices vote no, sounds good to me. Still, seems like a design fail from Toyota, if it's that problematic. Old fluid can accumulate water, the lines get rust/crap, compromise safety.

 

I'm not sure if it's a problem, but Toyota having to extend the warranty on the actuator decided it's best not to mess with the fluid (unless you need to). The actuator is a very expensive part to replace and they are failing as the cars get older.

I've read some failures on the gen3 cars recently so it just might be actual actuator design problem. Mine started making strange noises at 15000 miles and replaced under warranty

 

Did you mean 150,000 miles?

We've only got 76,000 kms on our 2010, and I'll occasionally hear a noise just as the car is stopping. Hard to describe, not loud but audible "cajunk" sound.

 

That's it, "cajunk". They described it as a squawk sound. It happened every time I pressed my brakes firmly. They flush the fluid once and that fixed the problem for about a month and sound returned.

The tech said it was a seized valve.

My car had 15000 miles and it's been doing that since before 10000. I ignored it initially thinking the sound would go away. As my warranty period came to an end, I had it looked at. I really didn't think my car with so few miles would have a problem.

 

Show me where you heard that.

 

Another experienced second gen voice would be hobbit, who took the step of actually buying brake fluid test strips and using them to check the condition of his old fluid. He discusses it for about the last third of this page.

Meanwhile, the working pressure for the brake system is produced by an electric pump that cycles on only when needed to force fluid into an accumulator, which is filled with pressurized nitrogen gas that gets further compressed when the fluid is pumped in, and that pressure is what forces the fluid out to the brakes when the system wants it.

To keep the nitrogen gas from mixing with the fluid, they are on opposite sides of a metal bellows inside the accumulator, and the metal bellows expands and contracts with every cycle of using some brake fluid and of the pump running to put it back again. That sort of boggles my intuition, because all of my experience with flexing metal is that eventually it gets brittle and cracks, leaving me to wonder why on earth you would use metal for that instead of, I don't know, rubbery materials known for staying flexible. However (comma!), that isn't just some weird Toyota choice; it seems like in the world of hydraulic accumulators, metal bellows are regarded as the way to go for long life and low leakage/permeability.

And yet, fatigue cracking of the metal bellows, followed by movement of the nitrogen gas into the fluid system, was exactly what the T-CP-D0H-A510-D recall was about. Apparently, those accumulators weren't made well and saw their bellows crack well short of the expected cycle life, whatever that is.

But even though those were defective accumulators and replaced with good ones, I would guess that even the good ones do have an expected cycle life. Some of the literature I've read from random makers of metal bellows accumulators will say things like a million cycles.

The Prius accumulator surely sees, oh, dozens or low hundreds of cycles in a normal drive, but shallow ones; two or three stops each use a little fluid, then eventually the pump runs and puts it back. They probably leak down a little more than that slowly overnight, to be pumped back in the next morning when you open the driver's door.

As far as I can tell, the last stage of the Gen 3 Techstream bleed procedure completely empties and refills the accumulator six times. I don't really know just how much normal-life usage that's equivalent to. Maybe not very much in the grand scheme. I just don't know.

I do know that the last time I went through a bleed procedure using a Mini-VCI, it kept losing communication right around the fifth complete empty and refill, and having to start over from the top, and that happened about six times before it finally got all the way through the procedure once, so that ordeal put something like thirty complete empty/fill cycles on my accumulator. Maybe even that isn't really significant compared to years of normal driving; I don't know, but I was gritting my teeth while it happened.

After that, I bought a Tactrix Openport 2.0 to try out instead of the Mini-VCI, and in all my other tests it does seem to be less flaky than my VCI was. I definitely hope that also extends to bleeding, so that in case I have to do it again, it will only do six cycles and not thirty. But I don't really feel like rushing out to test that if I don't have to.

-Chap

 

You can always use a turkey baster and switch out some fluid every couple years

 

Yes, but that is kind of a cosmetic approach. The brake fluid will look like new, but other than the fluid in the reservoir, it won't be.

I would be slow to replace the brake fluid as a preventive measure. I personally would do it only if the brake actuator had to be replaced.

 

I think the compromise that appeals to me is just going to be, at pad replacement time, to open the bleeders as I push the pistons back, so the old stagnant fluid at the dead-end wheel lines will be forced out instead of forced back up toward the actuator valves (some people recommend the practice for exactly that reason), and then use fresh fluid into the reservoir while bleeding, and call it a partial flush and declare it good.

-Chap

 

This is for your 2010? There is a non-techstream instruction in the Repair Manual, it's very straightforward. And @NutzAboutBolts video more or less follows it, just changing the order, doing the rears first.

 

That's exactly how you would bleed a regular brake system but wouldn't the G2 see that as loss of fluid pressure and throw alot of dtc's?

Seen many posters on here complaining about that. You cant sneakily bleed off brake fluid and the system not see loss of pressure.

 

Gen 3 there's an instruction in Repair Manual, you put the car in "invalid" mode, and it's ok, for bleeding or changing brake fluid. But I've looked through Gen 2 Repair Manual and did not see comparable instruction.

 

I put my 2010 into Invalid Mode once and, to get it back out of Invalid Mode ... I had to use Techstream.

But then I had used Techstream to get into Invalid Mode. There's also a non-Techstream way to do that, so maybe it knows the difference and remembers.

-Chap

 

Yeah, according to the instruction for non-Techstream bleeding, various (simple) actions will get the car out of invalid mode, even just turning the car off. I'll attach (3rd gen) instruction, appreciate it's off-topic here.

Again, it worked a charm for me, and I'm definitely shallow-end-of-the-pool when it comes to car maintenance.