Rear Brake Concerns

I'd appreciate any comments/suggestions with my brake woes:

Around the Ides of March (shudder) I checked front and back brakes, at around 43,000 km's. I removed and inspected pads, and removed/re-lubed caliper pins.

When I re-assembled the rear brakes I found the wheel quite hard to turn, read up a bit more, and learned about the orientation of the cross-pattern on the piston face, how it needed to straddle a pin on back of the inner pad. Apparently the pin was riding on one of the spokes. So I disassembled and rotated the piston clockwise to accomplish that. The wheel was now easier to turn, but still a bit reluctant.

I'd disconnected the 12 volt battery at the outset. Before reconnect I pumped the brake pedal several times. For the first 4 or 5 pumps I heard a fairly loud clicking sound from the rear of car. I'm thinking this was the auto-adjuster taking up clearance.

I also put a bit of anti-seize compound on the piston face. Considering the purpose of the cross-pattern on the piston, and that it's supposed to lock on that pin, be prevented from turning, I'm not sure if that was the right thing to do.

Anyway, just a few days back, around 46,000 km's, I noticed some light scoring on one of the rear discs. I decided to dive in again, raised the rear, disconnected the 12 volt, and had a look.

The pad at that scoring had some minor indentations. I'm thinking some grit got trapped in there, but has now worked itself loose. More troubling though:

On both sides of the car, the inside pad seems to be only making good contact on about the outer 50%. Also, the pins on back of the inside pads (the ones against the pistons), are looking partially chewed. Also, I noticed a smallish chip out of one corner of one of the piston spokes.

I'm debating getting some fresh pads (and likely backing shims too), cleaning up the pistons thoroughly and seeing how that goes. But what's troublesome to me is that I think I put everything together properly the first time round. It might be the application of anti-seize on the piston face allowed the brake pad's pin to ride up on the piston spoke a bit.

Here's a few pics:
(I'm having a hard time getting the picture orientation to behave, will try to resolve later)

The disk scoring, right outer side only:



The pad in contact with that face. Doesn't look too bad, some minor pitting corresponding to the groove locations:



The back pad, same side. Note the outer 50% only seems to be making serious contact:



Here's a pic of one of the disk inside faces. Note the rust zone:



A somewhat dark shot of a piston face:


(note the rusty chip out of spoke corner, just to right side of top)

And here's a shot of the worst of the two inside pads, showing wear on the pin that's at the piston:



Here's how the pad pins looked like back in March. The left side pad is an insider, showing slight wear, and the outside pad on righ shows how the pin would look when new:

 

I cleaned the piston face before reassembly yesterday, and that seems to have helped. Was also vigilant of the cross position.

I had my wife push the brake pedal, while I watched and listened at the brakes. There was a very faint ping sound with the first few pedal depressions, and the piston held steady. I could see the caliper tightening up too. Watched one side (of the car) for a few pedal depressions, then the other.

The last time (back in March), when I did the pedal depressions (by myself) I could hear a loud clank from the back. I'm thinking now, that mighta been the pin jumping a cross arm.

I'm hoping the rear brake system has survived, it seems ok, before and after driving, wheels turning near freely. Just a bit of drag, I think the typical disk brake drag. But I'm still concerned about the pad's pin being partially chewed. I've priced new rear pads and shims ($99 and $16). Might replace (at least) the pads very soon.

 

I think it's due to being rear disk brakes with parking brake mechanism that makes for unusual appearance. The disk appearance is maybe not as bad as it looks. There's pits in one pad, and that's creating a rusty spot on the disk, I think. There is one, quite fine score, nearer the center.

Looking through the pics I took the first time (back in March) I see the word ADVICS. Also see the Toyota symbol. Still, I really don't want uncertainty or delay, don't mind to spend a bit extra.

I greased the pins with Sil-Glyde Brake Lubricant. It looks the same as what was on there, and was recommended here. Think I'm ok in that regard. What's not so good was putting anti-sieze on the piston face. I'm guessing that allowed the pin on back of pad to jump a piston "spoke", at least once, and get the pin chewed up.

Still, looking at that same pin from the earlier pics, taken back in March when I first opened it up, the pin was a little bit chewed.

How do you intend to "rotate" pads? Do you mean swapping them from left to right side of the vehicle?

Anyway, I'm thinking to pick up the phone and get fresh rear pads and shims, chalk it up to experience. Thanks for the feedback.

 

The pads look identical, outside vs inside, but shims are different. Guess if you reverse the pads but not the shims? The contact points being different: piston vs caliper arms.

Anyway, new pads and shims ordered, picking them up tomorrow.

 

What I've done, and I'm not 100% confident I'm out of the woods, especially hearing about the TSB, is to purchase and install new pads and shims.

I also took off the discs and went over them with fine steel wool. I was careful to put anti-seize on both faces of the inner shim only (per instruction with the pads), and cleaned the piston faces carefully. Also put a very sparing amount of Sil-Glyde at the junction of the boot and piston, then backed the piston in for the new pads, careful with the piston's cross pattern orientation.

I had the battery disconnected for all this, and pumped the brakes a bunch of times before rehook up, and left the parking brake off. On reconnection no warnings, took it for a short test drive. What's worrisome is at the outset there was a pronounced whisper in time with wheel revolution. Over the course of the short drive it got a lot quieter, but still there.

Back home I again jacked up the rear and the wheels are turning nicely. I'm hoping new rotors aren't need, that it'll work out. I know I'm muddying the waters doing this all myself, if it comes down to bringing it in. Oh well, will keep an eye on it over the next few days, try to avoid getting too far from home.

 

Here's the part no's I've put in. They vary from the numbers in the TSB linked. The pads look to be identical to original, the shims are a little so revised, so not sure if they're the TSB types.

PAD SET, BRAKE P/N: 04466-76012
SHIM KIT, BRAKE P/N: 04946-47070

 

Read my mind, lol. There was next to no movement of the needle. This is with wheel off and open-end nuts (that I normally use with snow tires) tightened as well as I could, just restraining the disc by hand.

When I first took off the wheel, when I released the last lug nut there was a distinctive "poing". I think there's some unevenness in the disc's seating against the hub, aggravated since I removed and reinstalled it. I did put match marks, put it on the same orientation. Also, I needed to brake it loose by screwing in 8 mm bolts into the two holes for that purpose. It made a fair noise when it popped loose.

When I first put on the open ended nuts and hooked up the dial indicator, it turned very quiet and smooth, just a whisper. Then I loosened and resnugged them, and the noise started up again. I'm suspected the new pads are just brushing the edge of the rust zone, either at the extremity or near center of the disc. I'm hoping it'll work out. I'll run them a few days, and if the sound persists I guess it's new rotor time.

 

Yeah I brushed them with a stiff nylon bristle brush, wiped down with a cloth, and just ran my hand over. The dial indicator's telling me all is good. Still the noise, and this is one side only.

I'm hoping it's just rust just at edge of pads, and a few days will work it out.

I'm stressing though.

 

Went for a more extended drive, and couldn't hear anything, in traffic or with just road noise. I purposely went into a quiet underground parking garage, and there, going a long a wall in stealth, I could still just hear something. But considering the difference from my first test drive, I'm dubbing it rotor rust, dissipating as the new pads get seated. For now...