DIY brake service issues unique to Prius - Battery/Piston/Bleed?

That bit has worked for me so far.

Not sure why you would need to do that. I would leave it on.

Is that a quote from Eric? Seems familiar, and I appreciate his videos, learned a lot from them. OTOH, I've never cracked a bleed valve when pushing the pistons back, and in maybe 30 years never had a problem. I do keep on top of brake fluid replacement, did do it recently on our 2010, after setting the car in "invalid mode". But other'n that I don't open the bleed valve.

Yeah apart from rear brakes that you have to screw back in, I've used a large C-clamp. One caution with the Prius: it has a "resin" piston (euphemism for plastic?), you want to put something over the piston face, a piece of plate or substantial plywood, to avoid a point load on the piston edge.

 

Yes, emphatically so. Don't let the phrase "master cylinder" fool you; that used to be a simple cheap part with a couple pistons and springs. If you need to replace "the master cylinder" in your 2010, you're looking at one assembly that integrates that with a bunch of delicate electronically-controlled valves for making ABS, brake force distribution, stability and traction control all work, and the list price on that animal is $2498. And all those delicate little valves are what you're potentially forcing aged and grotty brake fluid through backwards from the caliper, if you just force the piston back.

Even if you don't actually damage it, it will be hard to rule the possibility out if you have any brake misbehavior after you've finished the job (especially, for example, strongly-dragging brakes, the sort of thing that could plausibly result from a grot-wedged ABS valve). You'd have a daunting diagnostic challenge just to eliminate it from the list of suspects.

If you open the bleeder, you will lose a small amount of fluid from the system as you push the piston back. The fluid you lose is the worst fluid in there (the lines to the wheels are dead ends; that stuff never circulates back, it just sits there and stagnates). After closing the bleeder and buttoning everything up, and making the reservoir level back up with fresh clean fluid, you've accomplished a partial brake system flush removing the worst stuff from the system.

It has worked for me. Having to reset the clock and all the radio stations can be annoying. Last time, I tried just putting the brakes in "ECB invalid" mode instead, which also does the trick, but it turns out that way is even more annoying. I'll just reset the radio stations next time.

-Chap

 

The only time I do is if I have to keep the fluid level from going above the high mark in the reservoir.

 

Hi Jim,

I really wouldn't stress over it too much. Yes, disconnecting the battery (even with resetting the clock and radio stations, grumble) is less annoying than trying to use the "ECB invalid" mode, which does (as you read) lead to a rabbit hole with Techstream as the best way out.

Ideally, with the battery disconnected, you reconnect it after you're done, the car wakes up with no idea you've done anything, and off you go. The situation you want to avoid is where your first use of the brake pedal after reconnecting the battery has to move the pistons farther than normal to contact the rotors, resulting in diagnostic codes. That's why everybody recommends pumping the pedal till it hardens up before connecting the battery again.

I don't know that I'd bother with the whole tube-in-a-bottle-of-fluid thing, but just ensure my tube starts with some fluid in it, and goes up from the bleed screw before down. Clamping off the brake hose also strikes me as overcautious; if the bleeder is open and you're forcing the piston back slowly, the fluid will come out there, not push the ABS valves off their seats.

It also helps to keep the downside in perspective. Worst case, you somehow don't get all the pad clearance out before connecting the battery, and you get a code. That should be a code you can clear yourself without Techstream or a trip to the dealer (unlike the wretched C1451, which resists all efforts to clear it until the specified procedure is used). Or, worst worst case, you make that trip to the dealer you don't want, and it costs you, what, $100.
There's maybe a 1 in 50 chance that happens (wild guess), so you do the risk analysis, multiply the amount at stake by the likelihood, and come out at two bucks.

How much more would you spend by not DIYing your brakes?

-Chap

 

How many miles on the car? Unless you're really high mileage, and/or salt-belt, I don't think you'll need 90% of that. FWIW, I've never needed to replace a rotor, and I think re-machining is pushed way to much. If rotors are suspect, check with micrometer and dial indicator first (see attachment for thickness and runout specs.)

Toyota recommends an in-depth brake inspection, tri-yearly or or 30K miles, whichever comes first. This is regardless of brake pad and rotor condition. A typical brake inspection will require zero parts, just fresh lube on the pins and pad/shim/caliper faying surfaces. For the pins I use Sil-Glyde Brake Lubricant, and for the pad contact points a sparing application of Permatex Anti-Seize Compound. That's it.

Toyota USA is mum on the subject, but Toyota Canada advocates a tri-yearly or 48k km (30K mile) brake fluid replacement. That process is easily achievable by a DIY'r, by setting the car in "invalid mode" at the outset. It requires a couple of pints of DOT3 brake fluid, a syringe with tube extension, another tube with bleed nipple attachment, and some sort of large jar with a lid with hole in it. And the ability to raise the whole car, and take the wheels off. And an assistant.

I did the brake bleed last fall, with my wife helping, pushing the brake pedal. It was not that hard. Watch @NutzAboutBolts video, and read through the attachment below. The only thing I varied from the video was to go in order per the Repair Manual attachment:

Front/Right, Front/Left, Rear/Left, Rear/Right

All the fluid exchanged comes out through the bleed screw. I would wager that if you keep on top of brake fluid changes, and even just having a relatively new, low mileage car, you'll have no problems pushing back a piston without opening the bleed screw. I've been doing it that way since the early eighties, never any problems.

For a first brake inspection, I would keep it just that: an inspection, albeit with the aforementioned lube refresh. You want to pull the caliper pins, wipe them clean and apply fresh lube (Sil-Glyde or equal). Also apply a bit to the boots (what's left on your finger will do), and run a slim blade screw driver with a little dab around the joint between boot and caliper (Eric tip).

When replacing the pins kind of screw them in, to avoid scraping off the lube. Just coax the boots up onto the shoulder of pin, and ensure it's not ballooning, squeeze the air out a bit.

Disassemble the pads and shims, clean thoroughly with a rag, and lay them out as you go, to avoid mix-up. Then apply thin coat of anti-seize (the silvery paste), always to the smaller of two components, as you stack the shims back onto pad backs. Also clean the piston face and boot, and the two caliper "fingers" opposite, and again apply sparing touch of anti-seize to those. Don't get anti-seize on the piston boot though.

Leave the clips that hold the pad ends in the caliper alone. Just eyeball them, if they're not rusty they're fine. They are very hard to remove without rotor removal, and it's really not needed.

Assemble everything, torque the caliper mount bolts (see attachment), pump the brakes multiple times, reconnect the 12 volt. One thing I've found: after 12 volt disconnect the car can act up a bit, do some strange rev-up for the first bit driving. I think it's recalibrating something, not sure. Seems to settle down quickly though, back to normal.

Bottom line: you can do this. You need a 14mm socket for the caliper mount bolts. According to the Repair Manual, you should also restrain the pin while loosening the mounting bolts (they screw into the pin), with a slim 17mm wrench (I managed to find one: just a bit flatter than the usual, fits in there). I've been doing that (restrain pin with wrench), since they say to, but I never did this on other cars, and I'm beginning to wonder. @NutzAboutBolts does not look to using that wrench either, IIRC. Doing so makes it harder to keep the 14mm socket stable on the bolt while breaking it loose, you just run out of hands. Anyway: I would highly recommend getting a solid, extra-long handled ratcheting wrench, preferably with swivel head. Jet makes a very nice one. Makes it much easier and controlled, breaking those bolts loose. Also have a decent torque wrench on hand for the reinstall, torque spec is 25 ft/lb.

My brake bleed kit:



About a week back, front brake inspection on ours. Rotors fine, 7mm pad thickness remaining, at 66K Kim's:



Lube remaining from last time:



Shop supplies:


(anti-seize for the pad/shim/caliper contact, sil-glyde for caliper pins and it's boot.)

Pads disassembled and cleaned:

 

Sounds like protracted neglect and failed pin lube. Lots of salt on eastern seaboard a factor.

I'd be inclined to have the car in Invalid Mode if opening the bleeder. To be fair, I'm not sure how that compares to 12 volt disconnect, that might do it. The latter has worked for me for taking the caliper off the rotor. I suspect leaving 12 volt connected and just not opening the drivers door will prevent any mishaps regarding pistons popping out. But I'm not not 100% sure it'd negate the car detecting excess pedal travel or whatever, so just err on side of caution, disconnect it.

But, I'm confident the fluid in our system is clean/fresh, with regular replacement. Not opening the bleeder has worked for me, for a lot of years.

I did have uneven wear on rear pads, and rusty inner face of rotor. It was down to me: I'd opened it up and reassembled, but neglect to get the inner pad pin properly locked between the piston face spokes. The pin rode up on spoke, creating skewed pressure, uneven wear, and so on.

I replaced the pads, took the rotors off and buffed the rust off, put everything back together with the the pin VERY carefully aligned with the spoke pattern. Test drove, it sounded like shite, due to residual rust on rotor. But raising the rear and spinning the wheels, I could see they were turning near-freely, no more drag. A week later could barely hear anything. A month later, like new. Bottom line: they can "heal".

There seems to a belief among Prius owners, and the Toyota dealerships don't disuade them, that brake maintenance equates to pad replacement, maybe coupled with rotor replacement as well. And since the pads can go a long way, no need to do a brake inspection. But really, it's preventative measure, similar to a dental checkup. Opening them up tri-yearly, checking pad thickness, relubing everything, defintitely including the caliper pins, that's the way to go. And for a DIY setup it costs nothing, no parts involved.

 

An interesting exercise is to look at the hydraulic system diagram in the New Car Features manual and try to figure out what path backwards through the ABS actuator you are forcing the fluid to follow when you force the piston back. The first time I did that was, um, after my first effort at pushing a piston back in my Gen 1. I had noticed at the time that I couldn't do it with my thumbs—a bit concerning to begin with, though usually I assume it just means the piston is sticky in the caliper—but I had gone ahead and used a clamp and cranked really hard to get it to move. When I later looked at the hydraulic diagram there was one of those sickening oops moments. In a Gen 1, with the power off, SFRR and SFLR are both closed, and they are not designed for back pressure to open them, but to close them harder. Where I was forcing that fluid to go was maybe up through SFRH's check valve, then pushing the closed SS valve off its seat (which looks at least possible), through the check valve of SLA and back to the master cylinder that way and then to ... well, wait ...

... or, it was up through the open SMC1, around through the P&B valve and back, up to the master cylinder and then ... well, wait ...

... where the pathways through the master cylinder (which in Gen 1 and Gen 3 combines a hydraulic force booster that uses pressurized fluid from the accumulator/pump assembly) are just plain too intricate to follow on the diagram, but either or both of those "well, wait ..."'s may have ended up returning to the reservoir through the high-pressure relief valve of the accumulator (at least that would explain how hard I had to crank the tool). It may have returned through another passage that's open when the M/C is completely released, but that wouldn't explain how hard I had to crank the tool. The final takeaway was that I had gone and cranked that tool until something gave, and to this day I am not entirely sure what gave.

And after that I had draggy brakes. And it took me a long time (and a whole long experience with caliper replacement and reman caliper quality) to eventually prove that it wasn't because I had horked the ABS actuator, but because I did in fact have one caliper with a damaged boot, and had replaced it with a reman that had zero piston return right out of the box, so it didn't solve the problem, even though a working caliper would have. So I ended up with a great sigh of relief that I had not damaged the actuator, but it was a possibility I had to keep in mind and budgeted for until I finally eliminated it, and I decided I'd rather not do that again.

Now, the details of the hydraulic circuits vary between Prius gens, so the specifics of my little story may not transfer exactly to anything but a Gen 1.

On a Gen 1, I bet if you could find a Techstream active test to activate the SFRR/SFLR valves, you'd be able to push the piston back with your thumbs.

Funny, in the time I've had my Gen 3, those clips on the rears are the only brake parts that have needed replacement. (I did replace them without removing the rotors, it wasn't bad really; I think I used a small screwdriver to pop them out.)

In my experience, entering Invalid Mode set a C1451 code that was unclearable in any way short of completing the Techstream bleeding procedure. Maybe not a big deal if you're planning to bleed anyway, but it gave me fits trying to figure it out until I fed techinfo another $15 the following day and read that, yeah, that's exactly how it was designed to work.

-Chap

 

I can vouch that the brand new official Toyota clips I got from my dealer also have the slick black coating, and I don't believe the Repair Manual advocates any added lube there (I don't have it in front of me to check). They specify their black "Disc brake grease" for the shim surfaces, and their red lithium soap base glycol "rubber grease" for the pins, boots, and piston rubber, and nothing on the pad ears.

That's about the way I left it. We'll see how it's doing at the next inspection. (I did clean up the pad ears, from the rust that was on them.)

Sometimes, like in places where grot gets thrown up from the road, adding sticky lube is not as good a thing as it seems like it should be.

-Chap

 

If you mess with the brake fluid you'll have to take it to the dealer and get it adjusted you will have no brakes

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The main ingredient in Anti-Seize is molybdenum I believe, so maybe some of this is a language thing. I'm coming from Honda, where the Shop Manual is a lot clearer/specific. They recommend anti-seize where shim contacts, pad, second shim contacts first shim, and shims contact either the caliper fingers or piston face. I believe they also suggest a dab on the contact point between pad "ears" and anti-rattle clips, at the two ends. I don't usual bother with the latter though.

Here's an "exploded" pad shim assembly, with the shims taken off, flipped, and laid out in order. When reassembling I apply very thin coat anti-seize in the hatched areas. Basically when done the anti-seize more-or-less disappears. After you've applied the brakes a few times you'll see it just peeking out around the perimeter:




And on the caliper, I apply anti-seize (again, very thinly) here:



Chap, regarding the brake bleed, I'll defer to you. I've yet to replace pads on Prius, so do not know. My pdf Repair Manual is no help, does not have a specific instruction for pad replacement. Maybe there is something better on TechInfo, a step-by-step of pad replacement. My instruction show a complete tear-down of a caliper. Something that is very rare these days.

I've attached a pdf excerpt from 2010 Honda Pilot Shop Manual, pertaining to front brake inspection. I've got other paper manuals, but this is one I managed to cadge in pdf format, a lucky find. I find it's format much more specific to the task at hand, a nice step-by-step. Also note the instruction to push back the piston makes no mention of opening the bleed valve. To be fair, maybe the Prius is a different system. It's interesting, the difference in presentation style.

 

As a kid, I always just mashed the piston back without a second thought. But, you know, until I was 44 I never had a car with anything between the calipers and a simple, two-piston master cylinder.

I don't think I began reading recommendations to open the bleeder until systems like ABS/VSC/TRAC had been common for a while. They're very common nowadays, not just in Prii, and they all put a pretty intricate mess of delicate little valves into that pathway that used to be so simple when I was a kid.

-Chap