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

I'll write a book about it. Myabe I'll get my $$$ back.

Now seriously - a couple of Qs to bounce back ideas:

Un-true rotor: do you mean the brake disk is not co-planar with the brake pads? (you mention "the rotors are not installing flat against the hub?" - is this the same? I don't see how it would be different with my technical English). I did a comparative dial test and got nothing; I locked the disc in place with lug nuts and clamped the dial on the caliper's bracket - there should be a link somewhere.

Then axle is bent or something is bent - it crossed my mind. How would I check this? I suppose only with those guys doing alignments or what? ... Looking in the sun the paint on the trunk lid doesn't seem the same and the rear bumper is suspiciously drooping, the eyelets on the bumper's edge are not firmly snapping in place around the rear lights (I will take it eventually off for a few things I have to do and I'll see what's going on underneath but I didn't notice this when I bought it - I want to make this car a travel conversion and I was looking to reinforce the rear like on a van and when I pressed on it a bit I noticed it starting to sag unusually).

Maybe a wheel bearing or lack of lubrication is heating the rotor & caliper? How would a bad bearing feel when it's bad (assuming nothing else is touching the disc) ottomh when I did the test, the bearing felt quite smooth, is this something I should be able to feel by hand? When I spin the wheel I get something like 2.5 turns out of it. I'm thinking of doing the same with the caliper off to do a redneck bearing test, I reckon I should get at least 4 spins out of it with a good push, right? (Based on this old video posted, I think even in this thread).

For the wild guesses, I did check with Techstream and it seems that under the hood everything works ok; the valves are closing/opening as per the repair manual.

PS: I'm suspicious of 3rd party parts esp after this experience, but after all this, I'm starting to believe that Raybestos was really not the issue in this whole story given how messed up was the original Tokico; something caused that kind of a failure. In the future I'll stick with oem.

I'm looking online and I can get an oem bearing assembly for about 210 cad - shipping/taxes in. If anybody has pointers for ruling the bearing out ...? now is the time. I wanna do the "ramp it off a cliff test" (kidding - I won't).

 

Update troubleshooting for the bearing - the bearing is good: Without the RL caliper on, the RL wheel spins 8-9 times smoothly - no issues there. With the caliper on I get 1.5 turns maybe. The good RR wheel gives me 2.5-3 turns in comparison. Next.

Now, I remember, when I changed the caliper the first time, I stupidly pressed the brake with the caliper off the disc and I spilled the brake fluid emptying the main cylinder. I found a technique where you route the bleeder back into the brake fluid container and bleed like that until there are no more air bubbles showing. I thought things were good BUT I'm thinking that it's possible I did a poor job and some air is stuck inside.

@ASRDogman The wear on the pads for RL wheel - not sure how normal is that, seems to be a slightly uneven wear so I measured all the corners of a pad to make sure I get the whole picture. I pinched the whole pad to be faster more accurate with the calipers, there's about 7mm on the pad (btw, always checking that the cylinder seats flush on the pad, ie not riding the pad's pin):

Outer Pad: (seems oddly uneven)
13.10 - 14.16 (Top bleeder side - Outside Of the Disc then inside of disc)
13.47 - 14.51 (Bottom Outside - inside)

Inner Pad:
14.10 - 14.10 (Top Outside-Inside)
13.65 - 13.81 (Bottom Outside - Inside)

Other than that I'm all out of ideas. Either way I think I'm going to the mechanic next.

 

Somebody mentioned TIS "brake relearn" at some point somewhere, I forget. Is that a thing? Do you do it with a regular bleeding in TIS or how does it work? what should I look for in TIS?

I tried some google'fu and found: "Bleeding without the Techstream may result in air remaining in the brake hydraulic system." (in here) So by deduction, the Techstream bleed should take care of any potential air locked in the system?

 

Ok. Also, I imagine when they changed the booster they must've ensure there's no air trapped in there?

Gonna play with Techstream to see if I can find any re-learn info in there - my last resort.

 

Chap ... x1,000,000 - I was reading in the manual and wondering about this. The manual puts 1 to regular bleeding and 2 for system bleeding - not that it makes sense but I better as as a just in case: are these steps to each other, should I do a normal bleed if I want to do a system bleed?

I attached the regular bleeding and "brake system bleeding". Also cowl removal procedure for 10-15 Priuses in case somebody else needs this.

I would think Toyota did the system bleeding when they changed my booster . I'll remove the cowl, if I have easy access to the stroke simulator bleeder then I might give it a shot just to make sure (maybe ???). I got interrupted today from all this - it seems I'm the only one with 2 right hands in the fam capable of building.

 

After I'm done torquing, I depress the brakes and stick my head in there to make sure the piston sits flush (literally). Been checking this since day 1, and I always make sure it's not part of the error - I've mentioned sometimes that I make sure the cylinder is flush, not riding the pad's pin. Every basic brake installation procedure is respected surgically (I can be a maniac with making things pretty and respecting norms).

 

@Mendel Leisk - I rarely apply the parking brake.

Both the mechanic and Toyota said it must be the caliper. My mechanic said I was troubleshooting it well and said to check the pad brackets to make sure the V clips are pushing out the pads. I checked for rust behind the main bracket, and made sure the stainless brackets were letting the pads slide out easily and still got heat.It did feel like the wheel was turning slightly easier, but when turning the rotor by hand it was still a drag.

I'd have to replace the calipers according to them, and I can't help but wonder if I buy Tokicos and it's not that - then do I do?? The Toyota rep said he saw a similar situation and it was solved by changing to the Tokico - but I keep having this feeling it might be something else: just because the original seized caliper was in a really bad shape and now tow calipers malfunction exactly in the same way 1 year apart on the same side.

 

It's the same case ASR . Just look at the list of things I've done. That's why I'm going insane. RockAuto just sent me a warranty replacement and it's doing the same thing (for rear left - I didn't even to take off rear right which is fine.

Before I did this bracket check, RL was giving me 1.5x ish turns and RR (The good one) si giving me 3 turns. The RL however, it seems it has improved (like I kinda get more than 2 turns, but if I take the wheel off it still feels hard to turn the assembly by the bolts - vs RR which is fairly easy) . I have put back in the same old pads and rotor, I didn't want to put in the new pads and rotor until I got no heat.

I get this issue down to the caliper indeed. But is it the actual caliper? OR the fluid? And the fluid doesn't come out when I open the bleeder. So yeah, it looks like it's the caliper.

 

I took the OEM calipers apart (kept those in a box for days like these). The rubber parts look good. Gonna try to clean the RL and bolt it on the Raybestos bracket.

Overall there are tiny details which shows that the Tokico are meant to last. Also reading on some trucking forum that they have trouble with Raybestos/Chinese calipers breaking easily/too soon. Tell people to get OEM at all cost when you see their posts. My Raybestos discs with anti-corrosion had corrosion spots after winter - not right, I think.

 

I disconnected it, drove like that, and still hot. Not the cable by far. The cable has the tip rusty but inside it was lubed (the rubber boot comes off if I pull too hard just like on a caliper).

Cleaning does make sense! I know I don't wanna damage that square rubber ring. Yeah, I've watched caliper reconditioning clips, I'll make sure they are surgically clean. I have to scrub the caliper with a wire brush first before I can begin.

The parking brake, if you refer to how the pedal in the car feels, it is loose because I loosened it way way back. The one on the caliper is springy, hard, seems to be in good shape (both the one inside, and the one outside - there are 2 springs).