Uneven Brake Wear

welcome!

you might be correct, hopefully it is not a steering issue.
at this point, i would pull everything apart, measure the rotors and check for runout.

 

If the caliper piston doesn't compress easily I would change it and when I change calipers I always change hoses.

 

Some people use a screwdriver to unseat the brake pads from the rotors and after caliper removal use a c clamp to compress the caliper piston, it should be fairly easy to compress. The struts and brakes should be totally unrelated and struts should have no oil leaking out of them but can still be worn. The ticking noise could be a CV joint in the drive axle but take care of the brakes first and inspect the condition of things in that area. If you aren't a do it yourself person I would take it to a local shop for inspection and repair, don't mess around and get it fixed.

 

sorry, i thought 'resistance rotating the wheel by hand' meant the steering wheel.

 

That is a great guess. Excess wear of that magnitude isn't likely to have any other cause.

Don't be too fixated on the two little slide pins. They do need to slide easily (which you'll easily be able to tell when you get into the work), but the caliper works as a system and those little pins are far from the only reason it can stick. I think some people fixate on the pins because they seem easiest to replace and they want the solution to be easy, but it's worth looking more deeply if you want the solution to be right.

The caliper piston and bore, of course, share a lot more surface area than the pins and if the piston gets sticky, that takes 'stuck' to another whole level. Any damage to the rubber boots around the piston or the pins to let salt water in can contribute to either the piston or pins getting stuck.

What makes the piston retract when you're not braking is the rubberiness of its internal seal (you don't see that one, unless you take the piston out). If the seal gets old and toasted and glassy, you lose retraction, and you get drag. I now check for proper piston retraction (should be about 0.3 mm) when taking any rebuilt caliper fresh out of the box, before even putting it on the car, because I've seen a fresh rebuilt caliper with no retraction. (I have a theory about that, because it came with a very shiny polished piston where Toyota's have a less slippery, matte finish; reduce the grip between piston and seal and you can compromise retraction. The way aftermarket rebuilders mix and match parts can contribute to that. Toyota sometimes has their own rebuilts in stock—search for the part number with -84 tacked on the end—which are rebuilt with the right parts.)

Gen 2 front calipers use a piston made of a phenolic resin (the earliest, most famous phenolic resin was Bakelite; of course they've come a long way since). Those have some advantages over metal, but there is one weakness: a study showed that severe heat cycling can make them take up water and swell. Swollen, they'll start to stick.

You can see that pretty much all of these conditions are accelerated by heat. Heat ages rubber; severe heat cycling swells pistons; heat speeds chemical reactions. A dragging brake makes heat. What that means is there's a cascading effect: if the caliper has been dragging and cooking itself for a while now, it's possible there was only one reason for that when it started, but by now you could have all of them.

But there's nothing there that can't be fixed, often with nothing more than the ~ $20 rubber kit from the dealer and a bit of time rebuilding. If your dealer has rebuilt -84 calipers in stock, I would trust those, and you could save the labor of restoring them yourself in exchange for a bit of coin. I would nearly always use the rubber kit and restore an original Toyota caliper sooner than throwing on an aftermarket rebuild from the box store. Unless something made it truly unrestorable.

If you need pistons, they aren't in the rubber kit, have to be ordered a la carte.

Somebody on a Porsche enthusiast site wrote "... I am adamant about getting the proper caliper on your car. There's a good chance those are the calipers you have on your car, you just have to treat them properly."

More in this thread.

-Chap

 

Whoa, that's a super weird generic parts diagram. Where did you dredge that up? Better ones on parts.toyota.com:



You can see that the 04479 rubber kit includes everything in your red box except 2 (the piston). Pistons are a la carte if you need those. The little packet-shaped thing in the 04479 picture is a packet of the proper red grease for the sliding pins and pistons and the rubber boots. If you were to buy a tube separately, Toyota calls it "Rubber Grease", but you don't have to, 'cause it's in the kit.

Likewise, you can see a little packet in the picture of the 04945 shim kit. That's the shim grease.

I don't remember, offhand, the answer to your question about where exactly to apply the shim grease, but there are distinctive arrows in the picture in the Repair Manual showing exactly where to apply each grease.

The 04947 fitting kit I see isn't even shown in the diagram you had. Those are the little springy guys that fit in the caliper mounting bracket and hold the "ears" of the pads. Those can get corroded and lose their slipperiness. They aren't greased (they're out in the air, so grease would just attract road grit) but new ones have some kind of Teflon-y coating. That kit is inexpensive.

Cheers,
-Chap

Edit: oh yeah, your green circled thing is the bleeder screw. There's a rubber cap on the end. New rubber caps are in the 04479 rubber kit, but new screws aren't. You shouldn't generally need them. If they're well rusted you might.

If the existing rubber caps are there and in good shape, the bleed screws should crack loose very easily and give you no trouble. If the existing rubber caps are missing or dead, salt water gets in through the bleed passage and rusts the screw to the caliper from the inside, making it a real challenge to get loose without breaking it off in the caliper. Moral: when you're all done reassembling and bleeding, be sure to put the new caps on! Observe the tightening torque for the bleed screws in the repair manual: it's not very much, and if it is printed in inch pounds, do not mistake for foot pounds!

Edit again: the phenolic piston is crackable if you're overenthusiastic taking it out. May not matter if you're unconditionally replacing it, but would prevent you from just checking it and reusing if it's otherwise ok.

Using liquid pressure is more civilized for piston removal than air pressure. Compressed air will fire it out like a cannon. A board wrapped in some soft rags against the far side of the caliper can make a good stop without cracking it. Don't have your fingers there.

 

1) I guess shims are probably pretty much shims. Up to you.
1a) The Toyota shim grease is some gray stuff. You can get it at the dealer (find the part numbers of the various greases here), or, plenty of posts here on PC report using plain anti-seize as shim grease.
2) Repair manual (along with technical service bulletins, wiring diagrams, recall and warranty extension notices, and Toyota technician training courses, etc.) found at techinfo.toyota.com.
3) As far as I know, if they appear to be in good condition, are the right size (fit nicely back into the bore) and you can assemble the caliper with them and measure a nice robust retraction, they're fine. If they're chipped or cracked or roughened up, or swollen and hard to fit into the bore, they're candidates for replacement.

Judging the fit is tricky: they are normally a precise-enough fit in the caliper bore that you will start trying to fit one in and you'll think it will never go in, just because of whatever tiny angle you are holding it at. But you just kind of play with the angle and jiggle a bit and at one point when you happen to hit perfect alignment it just goes shoop and slips right in. This is easiest to test without the rubber seal installed; then once you know, you can slip it back out, install the seal, and then reinstall the piston, contending with the seal.

In the very few threads on PC where the pistons had swollen, you could tell; they were really just plain hard to fit back in the bore, or really didn't want to move.

I said upthread that the conditions for phenolic pistons to swell involved heat cycling. That's the way I remembered it, but I just now skimmed that study again, and I had it partly wrong.

The study had to compare delivery trucks (make lots of stops, heavy, lots of heat each stop, high heat cycling) with RVs (also heavy, lots of heat each stop), because the RVs were having big problems with phenolic pistons swelling and the delivery trucks were not. The big difference was the RVs spend a whole season every year usually not being driven, and the pistons slowly absorb moisture that is not driven off by routine heat cycles in use. So then the first heat shock of putting the RV back in service the next season wedges the swollen caliper and creates a drag. The delivery trucks had more constant heat cycling that prevented the pistons from ever absorbing that much water, and they didn't have swelling issues.

So, that gives you an idea of the sort of strange use conditions usually needed for piston swelling to be a problem. But anyway, you'll find out once you have them apart.

-Chap