Just changed brakes, now they are sticking. HELP!!!!

I was kind of hoping for a particular observation that might be harder to make if too many things are checked in combination. I'd have wanted to know: if one wheel is jacked up, and no one is applying brakes, and it's hard to turn, and the bleeder for that caliper is then opened, is the wheel still equally hard to turn?

What are you using for your standard of "as it should"? On my Gen 1, a 'good' return seemed to be about 0.3 mm. Possible to see with the naked eye if testing the caliper on a well-lit bench with nothing else moving, but tough to judge without a dial indicator.

Using 'hit the brakes' as a way to test the piston return ends up not working too well, because the braking forces are strong enough that the elasticity of aluminum and steel are in play; the caliper and bracket stretch by several times the piston return amount that's of interest, and then spring back. I found the piston return to be most easily tested on the bench using short puffs of compressed air. I think this could be done on the car (secure an upward-running clear hose on the bleeder, open the bleeder and let some fluid partly fill the hose, then apply puffs of compressed air at the end of the hose, counting on the fluid in the hose to carry the force without letting the air in the system). But I've never had a chance to test that, so for now it's just an idea I think would work. The key is to use the minimum force it takes to nudge the piston out to just kiss the surface of whatever you're using to block it, but not stretch or deform it, and measure how far it retracts from there.

-Chap

 

A feeler gauge might help, checking that the piston retracts slightly.

 

Those pads got HOT, see the bluing?!!!!????!?!?!

Assemble the calipers WITHOUT the pads and see if they slide smoothly in-out. If so, the caliper pistons are not retracting (based on your other observations, which were very good), the most likely cause is hardened piston seals or debris behind them.

 

All of the piston-return checking I've ever done, I've done in blessed solitude. What way would you check it where another person's help would be needed?

Do you know whether the calipers are original? Have you changed either one at any point in this thread? (Apologies if you've already said, I haven't re-read the whole thread just now.)

If they are original, and have not been through the mill of a cheap 3rd-party remanufacturer, it might be worth changing out the rubber kit and then measuring the piston return again to see if they have come back to life.

Here are a couple of pictures of measuring piston return:





A dial indicator from Harbor Freight, eBay, etc. is cheap, and the only other prop is some block or blocks of hard stuff (I used a couple nylon blocks I had around, but it doesn't matter) about as thick as the rotors with pads, with a hole drilled through for the dial indicator stem to rest on the piston.

The trick is not to apply a lot of force during the test (a brake caliper makes it easy to apply a lot of force!). The point is not to test how much the blocks will squish or the caliper will stretch, but only to gently extend the piston to where it lightly taps the blocks, then note how far it relaxes. A gentle puff of air into the caliper from a bike pump is easily enough.

A couple years ago, a poster discovered his phenolic pistons had swollen (rebuilding the caliper, after getting them out, they wouldn't go back in). That doesn't seem to be your issue, as you make it sound as if they move easily, but another thing to watch for. Pistons aren't included in the rubber kit, might add another $16 or so if needed, if I remember right.

The big auto stores sell complete 3rd-party remanufactured calipers, but the last one of those I tried had zero piston return right out of the box.

-Chap

Edit: the pictures above show the magnetic dial indicator base stuck right to the caliper, which was easy for Gen 1 because those calipers are cast iron. Naturally, it won't stick like that to an aluminum Gen 2 caliper, so a little more setup would be needed.

 

I am of the belief, not powering down the system correctly and bleeding the system is the cause of your misery.

Air might have been introduced

How did you bleed the front calipers? The Prius requires Techstream and a specific sequence.
How much did you bleed? The systems has ~1 gal of brake fluid (per Galaxee).

New pads are 10mm to wear indicator. Minimum required thickness is 1mm to wear indicator.
So how much material was left?

Lets say 3mm to wear indicator. 10mm - 3mm = 7mm of pad material used over 120K miles.
120,000miles/7mm ≈ 17,143miles per mm of pad material used.
2 mm more to go = 17,143miles/mm x 2mm ≈ 34,286miles left in the pads.​

Yes, you screwed the pooch.

Yes.

STOP applying pre-ABS and ABS brake bleeding procedure to the Prius. The Prius is a different beast.

Look at the braking diagram, by expanding the image. Do you see how many valves there are? Valves that are computer controlled. You have already pissed the system off bleeding it incorrectly, and it has not forgiven you. To properly bleed the brakes, you need Techstream, and you need to follow the service manual procedure on bleeding. Acquire a working miniVCI cable and get a temporary subscription to Toyota TIS, the OFFICIAL service manual. $15 for a 2 day subscription.
Toyota - New Subscription

 

Umm, unless you disassembled the calipers, you have not inspected the caliper piston seals. What is shown in your photos are the piston DUST BOOTS and their only job in life is to keep the road grime out of the caliper bore and off the external piston surfaces.

 

Chances are high, but not 100%.

The "school of hard knocks" offers a superior educational experience, she is also VERY costly. Knowledge costs a LOT, wisdom even more

 

The factory service manual lists specific steps to, power down the system, before working on the brakes. Are you sure you have the Toyota service manual?

As you now know, you can NOT do that on a Prius. The factory service manual lists specific steps to bleed each wheel. Techstream is REQUIRED, because the software tells the Prius brakes to open close the appropriate valves, for a bleed procedure, at a specified wheel.

Again, are you sure you have the factory service manual? The procedure is clearly listed. If your service manual is not from Toyota, or second best from Helms, donate your Chilton/Haynes to your local library, along with your OBD2 reader.

Yes, that is my belief.

Dot 3 brake fluid is cheap. Remember, Galaxee (former member and Toyota Master Mechanic), says the system has ~1 gallon of fluid. WrongMart (WalMart) has Dot3 brakefluid for $4.93/quart (4 quarts = 1 gallon) or $14.67/gallon. Dispose of the old brake fluid responsibly.

The Toyota service manual also recommends connecting a charger to the 12V battery if working on the car ACC or IG-ON for prolonged periods. Best to use a smart charger that has an AGM setting (4.2Amp max charge rate).

 

With third gen, there is a specific procedure in the Repair Manual, for bleeding the brakes without Techstream. It requires the car to be "on" but not "ready" (ie: push start button twice without foot on brake). You then do a chicken dance, which puts the car in "invalid mode", and can bleed away. Not sure if there's something similar in second gen, don't have documents on that.

One gotcha: wherever they say "select Neutral" in the chicken dance, you need to depress brake pedal first, in order to do that.

 

There's a test I sometimes do for brake drag, drive for 15 minutes or so on a clear road (no traffic or need to use brakes), turn off into a big empty parking lot (without using the brakes) and come to a stop without using the brakes (just B mode, then R at the last moment, then stab the brake just at the speed=0 moment, no rotor heating).

I can vouch that on good, flawless Prius brakes, you can feel the rotors at that point and they'll be stone cold. (Even using the brakes a little to stop at the end of the test will invalidate it by making them noticeably warm.)

I only mention that because, if that isn't a test you had run before you did the brakes, you might not know for sure they were flawless. We know they weren't dragging anything like they were after your work, but perhaps they had already begun to just a bit, and would not have felt completely cold after such a test.

Reasonable to wonder about, but I don't think it's so uncommon as to rule anything out.

I'm not sure I remember reading anything you did that would have allowed air in to begin with. I do think it is possible that an air bubble could result in residual pressure at the piston. But you should notice that when cracking the bleeder (either a pressurized air bubble poots out, or a little fluid geyser). It sounds like you've now done that, and did not observe that result. So I don't know how much money I'd put on air being the problem.

It's not even necessary for them to act like one way valves. Depending on which valves, one simply sticking open would have that effect, because there is a pumped-up accumulator of 2000 psi brake fluid on the other side. That's exactly the worry at the center of the never-force-grotty-old-fluid-backwards-through-ABS school of thought: a little particle of grot getting stuck in a valve, holding it slightly open.

But, presumably, you'd have noticed that too, when you tried the crack-the-bleeder test (in fact, that's what I intended to be finding out, when I suggested that test). Had a valve been open with the accumulator on the other side, you might even have seen, not a quick geyser of fluid, but a sustained one. Sounds like that isn't what you saw.

There is another phenomenon (not one I've seen myself, but have seen reported) where the rubber portions of brake lines can begin to delaminate on the inside, forming a sort of internal rubber flap. Forcing fluid backward when pressing in the piston can fold the flap, and make a sort of pressure-retaining valve out of it. Sounds like a freak, almost incredible occurrence, but not hard to find reports of on the internets.

At this point, I don't think simple loss of piston-seal return performance has been ruled out yet. My approach would be to stay calm and not get too caught up in worries about more complicated and expensive things, before following up that possibility.

I'm with 05 here; the "piston seals" we're talking about are concealed inside the caliper bores, where you don't see them without taking the pistons out. (This, of course, is a procedure that definitely calls for bleeding afterward.)

Not sure I'm on board with that. It may be possible to confuse the Prius computers, but they aren't spiteful things you can piss off and that hold grudges. Also, if you confuse them, generally you can retrieve codes that will tell you what they are confused about. They don't sit there nursing their grudges in secret and plotting against you. And from the brake computer, you can read codes either with Techstream or without, using a simple jumper wire and counting light blinks. You've got Techstream and finally made it connect; did it show any brake codes?

Stepping further back, I'm not so much on board with the fingerpointing; I don't think any of us knows enough yet about your problem to be saying "oh, yes, X is what's happening, and it's because of Y stupid thing you did." We can all do that later, after finding out why it is that your brakes drag.

I would concur with exstudent that $15 at techinfo is a small sum of money very well spent, and a lot of great information is there at your fingertips. I would just say it that way, with less of the suggestion that you're being punished for your sins of not reading it.

Tough to say, but it wouldn't shock me. Again, they might have been marginal already (as you probably didn't do a cold-rotors-after-15-min-drive test just before doing the work, we just don't know). Also, for the last n thousand miles, the seals have been riding on about the same little area of the pistons, but when you press the pistons in, (a) you sort of flex the seals backward in their grooves, and (b) they end up resting against a different region of the piston that they haven't touched since the car's earliest days. If that makes them lose their piston-retracting spirit, so be it ... the rubber kit's only about $21, one kit does both sides.

It's true that many recommend an occasional complete change of the brake fluid—for a view that treats it as less urgent, see hobbit's brake fluid writeup (a bit more than halfway down that page). But a full change is a different operation from bleeding to get rid of some incidental peripheral air bubble. Maybe you'll feel like doing a full change someday down the road, but right now you're probably more interested in just having brakes that don't drag.

For the record, I think it's Galaxee's DH who's the Toyota Master Mechanic, but I do miss her great, informatively-written summaries of his master mechanicky exploits.

Caution here ... I tried that mode in my third gen, and I think I'll never do it again. I think there are two ways to get into something called "ECB invalid" mode: one without Techstream (as in the excerpt Mendel posted), and one if you do have Techstream (you can just tell it, hey, go into ECB invalid mode). I think the time I tried it, I just used Techstream, and perhaps that has a slightly different effect. Anyway, if you go into invalid mode the way I did, it sets a code C1451, on purpose. This code will drive you crazy, because it is nonvolatile (unhooking the battery will not clear it, and nor will the jumper/brake pedal dance that clears other brake codes), and the fortune that goes with it ("Motor Drive Permission Malfunction") tells you flat-out nothing, and only one procedure executed in Techstream will get rid of it, as far as I know. It's the closest thing I've seen to a disproof of my claim that the Prius computers aren't spiteful.

But maybe that's only a third-gen thing, and maybe getting into the mode with the pedal dance instead of Techstream doesn't set the same code, anyway.

-Chap

 

I used a couple of pints when I changed brake fluid on our 3rd gen, pretty sure I changed it all. OTOH: I couldn't find a stat as to how much fluid there actually is in the system.

 

You can try the Italians. Download at your own risk.
Documentazione Tecnica - Technical Documentation | Hybrid Synergy Forum

$15 is a small price to pay to get authentic materials from the source, malware free. Unfortunately today, Toyota no longer makes the download available as PDF. You have to convert CHM files into PDF files. This person figured out a way to do that.
Toyota TIS download tips | PriusChat

Huh?

The HV Battery seems to last 8-10years. Few get less than 8 years. Most get 8-10. Lucky ones get 10+ years. A new HV Battery may cost $2210 from a Toyota dealer who sells online, if they are willing to sell to you. 2007 Toyota Prius Parts - Camelback Toyota Parts - Genuine OEM Parts - Free Shipping
$2210/10years = $221/year = $4.25/week = $0.61/day
You may hopefully come to see that $2210 is not so expensive when you amortize the cost over the usual life span (assuming 10 years).

 

Recall the sequence of events.
Prior to changing front pads, brakes were operating correctly. Once front brakes were replaced, misery ensued.

Cause/Effect

Cause

• Did not follow manufactures procedure on changing the front brakes.
• Bleed brakes w/o Techstream; it is possible to do w/o Techstream, but a sane person would not attempt that misery.
• Post #42, depressed brake pedal, causing right front caliper piston to extend (possibly enough to allow air to enter).
• Unable to read codes that were initially present due to incompatible OBD2 reader.
• Drove vehicle with front brakes engaged, superheating the font pads. If front caliper seals turn out to be bad, this might be the root cause. Remember, prior to front pad change, brakes operated correctly and the seals were likely intact and operational.

Effect

• OP (Original Poster) is likely miserable right now. (opinion)
• OP does not have a safe car to drive. (fact)

​

OP can make the decision to try a complete brake system flush, ~$15 for 1 gallon of Dot3 or goto caliper piston seals (sold as caliper overhaul kit, $30.22/ea; qty 2 needed due to right and left sides), and 2 quarts of Dot3 ($4.93/quart) for front Left and Right. 2007 Toyota Prius Parts - Camelback Toyota Parts - Genuine OEM Parts - Free Shipping