Rear brake pad question

There are two schools of thought on that.

One is that there are many small valves in the brake actuator (this is not specifically a Prius thing, it is more a thing for anything with an ABS / traction brake actuator) and those valves need to open and close freely and seal well when they are closed, and forcing possibly deteriorated/cruddy fluid back up through them backwards is a slight risk that you can avoid by opening the bleeder. This way you also end up with a slight partial brake fluid flush: you squeeze out some of the cruddiest, most deteriorated fluid at the caliper itself, and you replace it at the reservoir with good stuff. This is the school of thought I belong to.

There is another school of thought with many members who will say "I've been squeezing it back up to the reservoir ever since working on granddad's old truck and never had a problem." It's not the one I'm in, but it's not a small fringe.

 

@ChapmanF any thoughts on putting it in Invalid Mode, for that very minor bleed? It’s in the non-Techstream brake bleed instruction, but maybe overkill for this application?

 

I imagine you'd get away with it if all you do is open the bleeder and squeeze the caliper piston and that's the only thing forcing fluid out, and nobody touches the brake pedal.

I think if the brake pedal is touched and it notices that line won't hold pressure (and it's not in invalid mode), it may valve off the line as an anti-leak precaution, and that would make it hard to complete a bleed procedure.

 

I've always just pushed the pistons back. Then again I'm also one of the few who actually changes brake fluid even though the Gods at Toyota don't require it...

 

This forum seems like it always overthinks things and makes simple tasks way more complicated then they need to be.

 

like when a person ask about dealer recommends the transmission flush and refill, we all jump in with goggles & white lab coats on explaining the cvt on the molecular, geothermal and chemical level?

 

Toyota USA says nothing about scheduled brake fluid changes. However, Toyota Canada recommending tri-yearly or 48k kms (whichever comes first). Not sure what model year that policy commenced, it’s not in our 2010 schedule, but as of 2014 it is.

attached are with/without Techstream methods from repair manual:

 

If that were truly the case people would change the CVT fluid

 

I've never had that particular issue with them. I have noticed that if the fitting kit (the little springy metal pieces that line the mounting bracket slots, for the pad ears to slide in) is new or the teflon is still in good condition, those little V springs really will spread the pads apart, forcing me to use one hand to hold the pads squoze together while fitting the caliper back on with the other hand.

 

Have the top caliper bolt installed loose, caliper rotated up, THEN install the two springs, pinch the pads together and rotate the caliper down into place. Might take a little jostling of the caliper to get it to ride over the pad backs.

 

Well, I was planning to just let the dealer do the brakes on my 2010 Gen 3, but...
I went in after spotting an ad for $219 brake pad replacement. My pads are about there (93K highway miles) (yes, less than 10K miles per year - bike commuter!) and I think the squealer has engaged on the right side. First surprise was that the TV offer expired 6/30, so it's now $300. Then they called up four hours later to tell me that my rotors were the cause of the squeal and that they needed to be replaced. So my $219 job that turned into $300 would now be $650.

I've never heard of rust on a rotor producing brake squeal, so I asked for a picture to demonstrate the situation. They showed me a pic and pointed at the rusty edge of the rotor, but I couldn't fathom how that'd produce the squeal. With the pads down to a few mm, I'm fairly certain they aren't the issue, so I told them I'd want to sleep on it.

I've changed my own pads on other cars before, but not on my Prius. I didn't really want to DIY, but when I suspect I'm not getting an honest answer, I usually revert to DIY, or at least get a second opinion. My general impression is that Prius rotors are probably overdesigned like crazy given how little use they get on a Gen 3, and it's extremely unlikely they'd need replacing.

I see lots of people posting questions about brake pad replacement, but few people following up with whether or not they'd do it again! I know there's a tendency for only the problems to show up here. (What's the opposite of "survivor bias" - failure bias? ) Curious to hear from anyone who does it themselves and would recommend it.

The other wildcard here is that I had my E-brake freeze up this winter. Accidentally set the E-brake when parked outside on a 20F morning after a few days of snow. Water worked into the brake line and froze solid. I had to go and couldn't wait for it to thaw, so I had to wiggle on the cable housing to free it enough to release the brake. The E-brake has felt a little funny ever since, like it might still be sticking a tad. Wondering if that's got something to do with the brake squeal, or the fact that the right rear is the problem since that's the side that stuck the worst. Maybe I should post that as a separate discussion...

 

Addendum:
I pulled off my right rear wheel to have a look at things. The pad wear is extremely imbalanced: the inside pad (on the left, blue arrow) still has 6-7mm, whereas the outside pad (right, green arrow) is gone. Also, the outside pad is slanted to the point that the outer edge is completely worn whereas the inner edge still has a few mm of pad on it. Does this indicate that the caliper is stuck? Following the issue with the parking brake freezing up this winter, I'm wondering if the parking brake hasn't fully released, meaning that the outside pad has been dragging for several months.

The outside edge of the outer pad (right side of image) is completely gone; the metal clamp on the outside pad (green arrow) is just starting to touch the rotor:

Outside pad, viewed from above, is almost completely gone. It is slanted, though, such that the inner edge has material remaining:

 

If your fuel mileage is where it should be it's unlikely you have a bad caliper. Most likely you have slide pins that are stuck or sticky. If your rotors are fine you can slap a new set of pads in there and grease the pins extremely well. If they're badly corroded or stuck you might have to replace them. I had to drill one of mine out because it was jammed in the bore.

 

That says uneven pressure to me; I still suspect misalignment of the spoke pattern on the caliper face. It is so easy to mis-assemble these brakes.

 

Thank you both for your input!
Hmmm.... so do you suppose the parking brake freeze-up during our one snow event was just coincidentally focused on the right rear? Or do you think that my tugging on the parking brake cable to dislodge it could have somehow created the problem?

I assumed it was water in the cable housing that froze to ice, so I started wiggling the brake cable. It took a lot of effort to get the pads to disengage on the right rear, and I've been suspicious that it didn't release properly ever since. The parking brake was already set, so the brake pads had nowhere to travel when I was tugging on the brake cable. Do you think pulling on the cable could've twisted the pattern and misaligned the spokes? The tugging wouldn't have bent the pins in the caliper, would it?

Maybe the ice wasn't in the cable housing? Has anyone had issues with ice formation in the calipers?

The fact that there's an issue actually makes me less inclined to replace the pads myself because it may increase the degree of difficulty of the pad replacement. ..

 

Maybe I should pull the left rear off and see if anything looks out of place on the right...

 

Better: just raise the rear (floor jack at the rear/central jacking point is best, but scissor jack on one side at a time will work in a pinch), and see how easy (or hard) it is to spin a wheel. With a good push they should be like this:

If they're royally dragging, it's more evidence of misaligned caliper piston being the culprit.