Planned on replacing front rotors and pads this past weekend on my 2014 T4R (130k miles). Everything going well until I found seized caliper piston on the inside (lower) side. Put the C-clamp on it but didn't move with moderate pressure. Couldn't get the spacing to put both new pads on so I put one new on the outside and then the worn pad back on the inside. I figured I would try to drive it locally for a few days to see if it loosens up. It looks as though the inside pad got hung up on the slide pins due to rust (I'm in the northeast) and then the inside pistons didn't move and one seized.

Probably going to end up with new calipers. Back in the day it would be a quick trip to NAPA for some remans. More options these days. It looks as though NAPA and Autozone have remans for about $80 after core return.

Rock Auto has 2 new options, Raybestos and coated Ultra-Power, both for about $80-90. They also have reman options, but I don't know if I want to deal with sending cores back to Rock Auto. OEMs from Toyota are about $140.

Leaning toward new from Rock Auto or remans from NAPA/Auto Zone. I like the idea of the coated option from Rock - anyone tried the coated Ultra-Powers?

Any other good or bad experience with replacements other than OEM?

Bro - you gotta take the cap off the brake fluid reservoir, so it can take back pressure from pushing in the brake pot with the C-clamp

Rarely do calipers seize and if they do, they can be rebuilt easy. There are only couple rubber seals in there and that's it.

Your Toyota caliper is approx $400 high quality part- don't do the NAPA reman unless you really really have too. Those cheap options are more likely to result in a true seized caliper vs your Toyota part. My 2cents. Good luck.

Sorry, but the cap on the reservoir is not air or fluid tight. Also, loosening the bleeder on the caliper will release the pressure. If you don’t believe that, remove the brake line.

I would do Raybestos new calipers. I trust their quality.

Second that

For that price I doubt the Raybestos are new manufacture, more than likely they're reman as well.

And a piston freezing up in a caliper is waaay to common, unfortunately.

Thanks for the replies - Raybestos calipers are $95 on Rock Auto and show new on both Rock Auto and Raybestos sites. So it looks like local remans at about $80, new Raybestos at $95 or $140 for OEM. Probably go with Raybestos. A little surprised to need the calipers - I haven't had to replace a caliper in many, many years. I guess the T4Rs are prone to seize, inside lower piston just what I ran into.

Just doing it the way I was taught decades ago- was told it stops the res from over flowing?

Anyone know what size metric flare nut wrenches are needed for removing the brake line from the caliper and the bleeder? I've only got SAE flare nuts from years ago. Also, is the bleed procedure on the front brakes just typical manual bleed or anything special? I haven't had to replace a caliper in years so I need to get up to speed with tools, etc.

Bleeder is a 10mm. Can’t remember the brake line but size, but probably a 12mm.

Thanks for the info; pulled the wheel off yesterday and found that they are both 10 mm. Also found the stuck piston looks to be no longer seized - both pistons on the inside were tight up against the pad. Probably drove around a week locally. Pedal felt different and braking was better so seemed as though it was no longer seized. Not sure if it will stay this way, but I guess I'll pull the caliper and get the other new pad installed on the inside for that caliper.

I see you can buy the piston boots from Rock Auto for $5-7/caliper. Is it possible to pull the boots and lube up the piston and seal? If I can extend the life of the original calipers, probably worth the effort.

Typically water got in there causing rust on the piston. You can try removing the rust by wet sanding it. Then replace the seals and boot.

If I ever have to replace my calipers, I am going with an upgrade:
Big Brake Kit, 6 Piston, 2010+ 4Runner 355mm - Underdog Racing Development

FWIW, I've been professionally using Napa reman calipers for years with good results. When my 2015 needs them, they'll be Napa remans, and I know for a fact I'll need them eventually. They do seize up fairly regularly.

I believe they have a 10 year 100k mile warranty as well...

Four piston Toyota truck calipers in all these 2000s+ trucks love to seize up in the rust belt. I am diligent with greasing and and washing during the winter and they still seize up in about 3-4 years.

Mine have seized up several times over he years and I no longer use anything but NEW Raybestos calipers. They last way longer in the salt and crap than others hands down

Service the brakes at least once a year and clean/free everything up.

You are hilariously funny, sir. Have you owned 4th gen 4Runner? Or do you live where it snows and roads get treated? I'm on my third set of calipers, like many members of this board.