frozen rear caliper

I think what you are writing is that the piston is not expending from the caliper bore when you step on the pedal.
All three other brake calipers are functioning correctly.

There is no mention of pre and post brake fluid level in the reservoir.

My three guesses:
a) You damaged the piston retracting it to insert new pads.
b) Piston rubber seal is incorrectly installed.
c) Clogged brake line at that wheel.

Also, there are posts concerning the lubrication of the pad pins.
Just perhaps the pads are hung up on the pins....but I don't think so.

So, remove assembly again and do a bleed at that wheel to further diagnose.

Good luck.

 

I agree, I'm not sure how the piston can be called frozen as you must have been able to move it back into the caliper to accomodate your new pads.

You should not expect to hear clicking from the adjuster as you would with the old drum brakes. This adjuster is a threaded rot smoothly turning in brake fluid.

That does leave the question why your pads aren't closing on the rotor, but you'll just have to find whatever strange mechanical situation is causing that; it won't be anything that's commonly seen here. Have you checked for anything as simple as a foreign object between the pad edges somewhere? Does the caliper slide freely on the pins? (Again, it seems you must have made it slide to get new pads on; that's what's most strange here, you must have successfully moved both the piston and the slide pins in the course of your work, and the available force from the brake system should greatly exceed the force you put on yourself, so this is a puzzler and I'll be watching for the explanation.)

-Chap

 

The rest of your post doesn't really corroborate it, but the above bit reminds me of my rear brake issues, caused by the pad pin riding up on a piston face "spoke".

It skewed the inner pad, causing half the rotor to show rust. Also a lot of drag.

Besides orienting the piston face and pad pin correctly, you need to ensure its well seated thus. Apply brakes multiple times, and only afterwords use parking brake, or pin won't lock in the spoke pattern, piston will rotate (bad).

 

About halfway through this is instruction on caliper disassemble. As you were thinking, looks like the piston just unscrews for removal:

 

Maybe c) in post #2?

I've had that condition, with another car, after dealership botched a brake fluid replacement. One rear brake (drum) completely not working.

The car took unusually long to stop, with anti-lock going off, and a strange side to side rocking as it finally stopped.

 

If I remember correctly, the rear brake fluids are electronically controlled... so you stepping on the brake pads while the engine is off won't cause the caliper piston to engage the rotors... Try turning on the engine and then step on the brake pedal and see if it engage.

 

I've got a feeling they do clamp with the engine off, from past experience. My memory's flakey though, not sure.

If you wanted to see: raise the rear enough to get the wheels clear, and have someone push the brake pedal while try turning the wheels.

Or just follow nutzaboutbolts advice, lol.

 

I am following this thread.

OP ...try to bleed the caliper at that wheel.
First step.

Is fluid coming out with pedal pressure?
If so, I would then look to the piston.

The instruction posted above are valuable...note the piston orientation upon reassembly.

Please let us all know if and how resolved

 

Hmm ... did you have the rotor machined (or at least, if the pattern was light enough, hand-sand it smooth with about 150 grit wetordry)?

Usually, those incomplete-wear patterns leave rings at the rotor edge that are thick, rusty, and rough, and they will quickly 'adjust' your new pads to match the old pattern, if not sanded or machined out first.

-Chap

 

I am going to piggyback on this thread rather than starting a nearly identical one...

I had to replace the left rear pads on my 2010 about a year ago (at about 52000 miles), after I noticed a "hot" smell after driving home one day (I traced it to that wheel because I could feel that the wheel was much hotter than the opposite side wheel.

At the time, I replaced the pads on both sides (even though the RR side was fine) because I wanted to do both at the same time. I can't remember the exact details, but one of the pads on that LR wheel was worn much more on one edge of the pad than the other edge. I re-lubricated all four of the pins too (the rear-most pin on the LR was basically dry).

Fast forward to this month (63000 miles), and I noticed the same smell and the hot wheel again. I thought the fix would have lasted longer than this.

I pulled the wheel and pulled out the caliper, and this time the rear pin was fairly dry and rusty. I lubricated both again, but didn't check the pads and reassembled (they looked straight and even externally, and I was clearly lazy). I ordered new pins, boots, and bolts and swapped them in this past weekend (about a week later).

Today, I smelled it again, and the wheel was warm again (but not quite as hot as the previous times). Grrrrr. My next step is to pull the wheel again and actually CHECK the pads this time, while reinspecting the caliper pins.

Has anyone who had this issue had to replace the caliper bracket? Or successfully "cleaned out" the holes in the bracket that accepts the pins? I imagine that these holes are a close tolerance to the pin to allow for proper sliding action.

 

That would puzzle me ... unlike the gen 1 drum adjusters, which give you one measly click for every (park brake on, park brake off, brake on, brake off) ... these caliper screw adjusters, if they are able to spin freely, should be able to take up as much travel as the piston makes in one go.

Now that, I would buy. If there was no boost power, your piston was probably moving very little (if at all) with each stroke of the pedal. It's not that the adjuster can't keep up with the piston, just that the piston was making very little or no motion for it to keep up with. (I say "or no" because I'm not sure that in failsafe mode your pedal stroke is intended to move any fluid except to the front calipers; in Gen 1 the failsafe mode was definitely front only. I can check sometime soon when I've re-warmed my techinfo subscription.)

Now, when the power's on and the accumulator pump has built up pressure, you just hold the pedal down one time and a valve opens and fluid just flows into the caliper until the piston stops ... one swell foop, and it should be properly adjusted, with the screw having spun to take up the slack. Even if you don't touch the pedal this might just happen automagically during the little self test that happens a few minutes after turning the ignition off.

It might set a code if it notices having to send an unusual amount of fluid back before hitting the rotor.

-Chap

 

When dealing with a similar issue on my old Gen 1, I came up with a pretty repeatable drag test that involved driving a decent distance without touching the brakes at all, even to stop at the end. (Even the gentlest stop at the end will heat the rotors noticeably and make it hard to be sure whether you've fixed a problem.)

If there is a persistent drag, it is also possible to measure the caliper piston return - how far it returns, should be a noticeable fraction of a millimeter, when the brake pedal is released. That's part of the job of the square-cut rubber seal around the piston, and if anything's binding or swollen or the rubber's gone hard, etc., that could be what you're seeing. I saw an aftermarket, non-Toyota reman Gen 1 caliper that had zero piston return, right out of the box.

You can measure piston return easily using fairly gentle air pressure. Measuring it in place with the full hydraulic system pressure really isn't better, because that pressure is high enough that you end up measuring the metal deformation more than the piston return.

The bracket is ferrous, even when the caliper is aluminum, so it can get rusty. Probably an 8 or 9 mm flex hone is right to clean up the pin bore if that's needed. If the bracket is very rusty and there is a plating business near you, they can probably strip and re-zinc-plate it for you all within their minimum batch charge, likely well under the price of a new bracket. You might then also need the flex hone to make sure the bores take the slide pins smoothly, depending on the thickness of zinc plated on.

-Chap

 

What lube are you using on the pins? Hopefully not molybdenum anti seize, that's just for pad backs. Try silglyde?

Also, broken record: be careful of the back of pad pin: it must be locked between the piston cross pattern spokes.

 

Good point; 08887-01206 is the Toyota-specified "rubber grease", a lithium-soap glycol formula that they know is compatible with the rubber they use.

If you bought a Toyota seals-and-boots kit, the little pink grease packet that came in it is this stuff.

-Chap