2012 Prius - New Calipers, Pads Still Dragging (hot brake discs)

Pad thicknesses are spec'd in the attachment to post #11. 10mm for front and 9.5 for rears IIRC, but check. Did rotors get replaced as well? Rotor thickness spec's are in the same attachment.

 

LOL, toyota fudged on the Gen3 EGR system, and perhaps 2010-13 on pistons and 10-14 on rings.

 

Last time I tried to put it in Invalid Mode, (about a month back, doing a brake fluid change), I completely overlooked setting the parking brake. It won't go into Invalid Mode, if parking brake is off. It's in the rules, in the Invalid Mode instruction.

So Rear/Right is good, turning semi-freely, but Rear/Left is dragging. With me it was the pad backing plate riding up on piston spoke, because the piston had managed to rotate.

Did you apply/release parking brake before your test drive, and the test spin? The "marriage" of that pin and the spokes is loosest till you've really pumped the brakes a few times, and/or gone for a test drive, with a bit of easy braking. And I think that parking brake application will try to rotate the piston. If solidly locked that's ok, but if things are loose, it might shift up onto a spoke, and drag.

This may or may not be the issue, just my hunch, because it happened to me.

 

Do you have jack stands? put them in rear, use jack to hold up front
Now may be good time to try getting all 4 wheels off the ground and start from step one.
Invalid mode, then bleed all 4 corners and then see what happens.

You replaced calipers, are the pins new?

 

I edited my response above.
Looks like parking brake does get applied?
Might want to hook that up and follow Mendel's post above to check piston orientation.

 

I should clarify, after reassemble of rear brakes, you want to avoid using parking brake immediately, leave it till after lots of brake pedal pushes, and if possible even do a test drive first. My theory: you can have the piston orientation correct, but if it's not solidly locked against the pin, a parking brake application may still rotate the piston, make a spike ride up on the pin.

 

Fixing a typo, too late to edit old post.

 

That's a significant clue I think. Something seized in the parking brake cable? There's an equalizer bracket shown in the attached, has an odd-ball Toyota name.

 

Yes......the brake house kit provides a piece of hose that runs from the caliper to the metal brake line mounted to the vehicle frame. A typical brake hose kit includes the hose, end fittings, and clamps - everything you need comes with the kit. Each wheel on the car has it's own designated brake hose kit.

 

If the brake actuator had one of the SLA valves not fully closing off, or something like that, the result could be constant brake fluid pressure in one line. That's one of the reasons there is a school of thought to always open bleed screws when pushing caliper pistons back, rather than forcing potentially grotty fluid back up through the actuator valves. (There are also people in the other, "I've always just forced the fluid back and never had a problem" school of thought. I'm more or less Switzerland.)

But that's about the only way there is for the actuator to be causing such a problem. It can't affect the rear disc by magic, or magnetism, or telekinesis. Only by fluid pressure.

Which means it shouldn't be impossible to catch it in the act.

Does fluid spurt under pressure if you open the bleeder on that line, when no one is applying the brakes?

If you watch the Techstream live wheel-cylinder-pressure readings while no one is applying the brakes, is there a non-zero pressure in that line? (That test would be trusting the sensor built into the actuator, but that seems mostly ok to me. The actuator is a box with a bunch of valves and sensors in it, and even if, say, one valve is messed up, I wouldn't jump right to assuming the sensors are bad too.)

There are also electronic pressure transducers you can obtain, and plumb directly into a brake line (there are such things as adapter fittings that replace the bleed screw), and connect to a datalogger, and watch what the pressure is doing, if you distrust the sensors built into the actuator.

 

Take it to dealership?