Trying to diagnose my brake problem

The pads being worn at 65k is rather premature. Have u looked at the rubber boots on the calipers? If these rubber boots have worn, it will cause the grease on the slide pins to dry up & when then get wet will cause the caliper to seize up. This could explain the premature brake ware, pedal feel & the brake pump.


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The US schedule calls for an in-depth brake inspection every 3 years or 30,000 miles, whichever comes first. This would entail:

1. Removal of the pads/shims, inspect, clean, relube*, and reassemble.
2. Clean and relube* contact points on caliper "fingers" and piston rim.
3. Removal, inspection, relube** and reinstall of caliper pins.
4. Considering the pulsation: check of rotor thickness, parallelism and runout. Requires micrometer and dial gauge with magnetic base. See attachment for specified limits.
5. Not specified in the US schedule (but specified in Canadian schedule), it would be good practice to change brake every 3 years or 30,000 miles, whichever comes first. See attachment for non-Techstream method. Also, @NutzAboutBolts has an excellent video on this (#18 here):

Nutz About Bolts Prius Maintenance Videos | PriusChat

Take extra care when reassembling the rear brakes, ensure the piston spoke pattern is per the attachment, and the piston is well seated against the pads before applying the parking brakes. Verify after a test drive and parking brake application, by raising the rear and spinning the wheels, that they are not dragging excessively. Slight drag is normal, but they should easily spin a revolution or two.

Disconnect 12 volt negative cable before commencing any brake work, and reconnect only when competely done.

* Permatex Anti-Seize Compound or equal
** Sil-Glyde Brake Lubricant or equal

 

I find my Gen 3 brake control isn't easy to quite modulate down to a perfectly smooth stop. As I gradually let the last of my pressure off the pedal, I can definitely feel a slightly more quantized releasing of the actual brake pressure, as the computer blips open and closed the pressure-releasing solenoids trying to match what I'm doing.

It's normally a very slight effect that I can barely notice if I'm looking for it. But it's definitely more pronounced if my car's been parked in the wet and the rotor surfaces are a bit roughened with rust and a little grabbier; in those cases, I can really notice the release-grab-release-grab-release... as I'm just smoothly letting up on the pedal.

So, what condition are your rotor and pad surfaces in?

That phrase "thing or equal" is usually seen when thing is what the factory recommends, but where you might also consider some substitute.

Here, though, Mendel's doing the substitution for you already (and not saying so). Per Toyota, their (**) grease is the 08887-01206 "rubber grease", it's red, and it is a lithium soap glycol formulation, not a silicone. From some things I've read, a close substitute for it might be Molykote G-407.

Toyota's recommendation for (*) is their shim grease, which is dark gray, 08887-80409. I think the 08887-80609 might be the same stuff in a bigger tube, but I'm not positive. They don't (for the models I know, anyway) recommend anything on the pad fingers; there is some Teflon-like dry slick coating on the replaceable "fitting kit" springy pieces out of the box.

Now, is it a good or bad thing to swap Sil-Glyde for the Toyota lithium soap/glycol formula, or Permatex Anti-Seize for the Toyota shim grease (whatever that stuff is)? I don't know! That's outside my expertise, so I'm not taking any position here on the appropriateness of making those substitutions, but only about making those substitutions in a PriusChat post where unsuspecting readers won't know they are substitutions and be able to decide on their own whether they want to make them.

-Chap

 

I stand corrected. I'm thinking use what you've got I guess. One thing, and my memory's a little fuzzy, but when I first looked at the brakes, the pads and their points of contact had next to nothing, and what there was looked like the Sil-Glyde, vaseline look, just a couple of dabs. Also, the pins seemed to have similar grease, again, fuzzy memory, but I don't recall it looking red or pink.

I'm sorta migrating Honda rational: butter up the faying surfaces between pads, shims and caliper with anti-seize, and the pins with silicon brake lube.