Rear Brake Inspection

[1997ThunderbirdLXV6]

...is what I did to my Thunderbird today, but I figured I'd start a separate thread because I expect to come up with more questions.

 Why

The reason I decided to look at my rear driver side brake more closely is that a few days ago, during my tire rotation and subsequent re-rotation, I noticed uneven pad wear on this wheel.

Disclaimer

Remember, this is the first car I ever worked on, other than cosmetic stuff, and when I do something mechanical, nine times out of ten, I'm doing it for the first time.

 Pads

Once removed, my previous observation was confirmed. The inside pad is more worn, though at an apparent angle:



Slide Pins

My first course of action was checking the pins. They seemed to slide just fine though. I did clean them and apply new grease, but it didn't seem necessary.

Note how part of the pin is shiny; the majority of it is dull. Is that corrosion?



Brake Piston

Since the pins didn't seem to be stuck or anything, I looked for other possible reasons for uneven pad wear.

I found that the piston indentation was not aligned with the nib on the inner brake pad:



As you see, the nib on the pad has actually worn a dent into the piston. That I think explains why the inner pad is more worn towards the upper end.

I was able to rotate the piston a few degrees before reassembly, but I realize that's just a stopgap, and new pads are needed.

Piston Boot (or whatever it's called?)

Upon initial disassembly, I was greeted with this:



The rubber boot, or parts thereof, was just hanging there. I cut off the loose part. There was no leak of any sort. Can I just replace the boot, or does this require a new caliper?

Reassembly

Was so tedious! The springs on the pads keep pushing the caliper out. Am I missing something? Or is this normal? I feel you need to apply an odd amount of force to align the caliper with the pins to fasten the pin bolts.

Those bolts, according to the Ford workshop manual, are supposed to be replaced with new ones (?). I'm guessing nobody does that? The manual also calls for a specific torque value, but my torque wrench doesn't fit in there. I went by feeling, which is scary because I have no frame of reference. They're tight.

I also found it odd that the pads sit right on the bracket. The corrosion could affect proper pad movement (?).



Recently I assisted my roommate in doing the brakes on his Cadillac ATS, and those pads sit on small metal holders which come with the new pads.

Is it normal that the metal brake line makes contact with the knuckle here? Seems oddly tight...but who am I to judge.



Other Observation

The rear wheels in the air, transmission in Neutral, when I turned the left wheel one way, the right wheel turned (opposite direction of course); when I turned the left the other way, the right wheel stood still, and the drive shaft turned instead.
When doing that, I could hear a distinct squeal from under the car. I'm guessing it came from the transmission output shaft seal (?). Is that common? Do I need to do something about this?

For this clip, the phone is located right under the driver foot space, and I'm turning the rear left wheel.

 

[XR7-4.6]

The squeal you hear might be the one way clutch if it’s coming from the transmission, which is normal(later mechanical diode ones will click)

The boot can be sourced in a rebuild kit but you have to remove the piston to replace the boot and it is not fun on those calipers!!! Better off just replacing the caliper… or just ignore it, the boot doesn’t effect its operation

The pin being misaligned with the piston will indeed cause that wear made the same mistake the first time I ever changed pads.

Don’t worry about the pad/bracket corrosion, they can corrode but under operation they won’t, just like the bare rotors

 

[1997ThunderbirdLXV6]

Edited to add clip of squeal.

 

[1997ThunderbirdLXV6]

Also edited to add image of brake line.

 

[1997ThunderbirdLXV6]

… or just ignore it

Let's go with that.

 

[XR7-4.6]

Yeah I’m almost certain now thats the sound of the intermediate one way clutch

The line might be slightly bent, no harm really, you can unbend it away from the knuckle if it bothers you

 

[Bill H]

I just regreased the slider pins on front caliper and when I tried to torque those bolts to spec I snapped the head off one. There is loctite on the bolts so just snugged them up well.

It’s been years since doing brakes so it’s like the first time. The fronts are still dragging a bit. I may not be done with them. We’ll see.

 

[1997ThunderbirdLXV6]

Yeah I’m almost certain now thats the sound of the intermediate one way clutch

So you're saying it squeals by design? Why is that? I mean mechanically speaking.

The line might be slightly bent, no harm really, you can unbend it away from the knuckle if it bothers you

It can wait until I replace the pads, but yes, it kind of bothers me. The whole point of the slide pins is that the caliper has lateral movement; but the line making contact there effectively restricts lateral movement.

 

[XR7-4.6]

So you're saying it squeals by design? Why is that? I mean mechanically speaking.

All the clutches and bands are always in light contact with the discs and drums, you’re hearing them slipping when you turn the driveshaft. When the engine’s running the pump is keeping all those clutches lubricated and cooled when not engaged so that slight slippage isn’t harmful. It’s the reason it’s not a good idea to tow with the rear wheels trailoring(unless you disconnect the driveshaft), you can burn up the clutches after a long enough drive

It can wait until I replace the pads, but yes, it kind of bothers me. The whole point of the slide pins is that the caliper has lateral movement; but the line making contact there effectively restricts lateral movement.

Yes but the caliper and by effect that portion of line moves towards the hub when the brakes are applied as well as through miles as the pads gradually wear, giving more clearance with the spindle. With fresh pads you simply took up that clearance but as long as it wasn’t actively interfering with the spindle(which would have made reassembly difficult) there’s really no harm in it just touching in the static position.

 

[theterminator93]

but the line making contact there effectively restricts lateral movement.

Believe me - with the braking forces the caliper exerts when you apply the brakes, that flimsy brake line touching the spindle isn't going to keep it from bending out of the way to let the caliper center itself if necessary. When you grab it to bend it out of the way, you'll see what I mean.