Leaking brake fluid from rear driver caliper.

i don't recall any spontaneous brake fluid leaks reported here. any accident or brake/wheel work? how many miles on her? is your reservoir low?

 

Could you get a pic? Or alternately:

Here's a semi-decent picture of the backside of rear brake, can you mark it up or describe location? I can't think what bolt requires an Allen key there. If fluid is leaking it could be at the connection of brake line to caliper, or at the parking brake "axle" that goes into the caliper?



And here's a pdf portion from the Repair Manual, just the brake (front and rear) section. Maybe better pics in there.

 

So this (highlighted) bolt?



Right up above it is the main axle (just have to name it something) of the parking brake mechanism. The piece that rotates when you apply parking brake

The Repair Manual portion I posted doesn't seem to show disassemble of this part. I wonder, if you were to succeed in removing the parking brake arm, where does that get you? There must be some sort of O-ring on the axle, maybe that's failing.

I'd be inclined to bring it in to dealership, have them put in a new or rebuilt caliper.

 

Semi-decent picture, the hex-socket head bolt again highlighted. Did you take the main parking brake axle nut (flagged with arrow) off? Still, not sure where this gets you. This axle goes into the caliper piston cylinder, something's leaking internally, would think just swapping for a rebuild is simplest. Not warranty I guess?



(Don't you love the pathetic condition of the caliper hold down bolt. We're NOT in the snow belt either.)

 

i don't know, the only thing that could leak is a piston seal. is there anything else as culprit? this is bit unusual.
if one is not mechanically savvy, this should go to a mechanic. brakes are important.

 

Depending on where you order it, you might only spend another $60 or so to get a real one from Toyota. You can see my sad thread here for an indication of the quality difference with a cheap aftermarket. Hehheh - Mendel thinks it's funny how "pathetic" one bolt head looks, after five years in Canada ... just wait 'til you see an entire caliper look like that after five weeks.

It is worth checking for Toyota genuine reman parts too - here's one for my car - which would be an even better deal. The magic words seem to be that you search for the part number with -84 added at the end, but I don't see anything for yours yet. Maybe they haven't been out long enough yet. Maybe that's why I haven't upgraded to a Gen 3 yet ... I must be waiting for them to start offering the reman parts.

Or maybe -84 isn't always the magic suffix. You could ask your local dealer if they can get your caliper in Toyota genuine reman.

-Chap

 

Well, someone (Mike Focke) was mentioning they've outlawed some bolt coatings, more rust-resistant ones. It's dismaying. And yeah, we're practically a suburb of California, very little snow and salting.

Foxhound, if you go with a remanufactured part you've let someone else do the leg work, and can be confident it's good. Since you're obviously hands-on, you can save some $ by putting it in yourself.

But I'd question even that: on a conventional car opening the brake lines means you need to bleed it. Personally I don't even want to do that anymore, when a dealership will do it (and screw it up royally, on occasion) for under $100. But with the Prius bleeding brakes is more complicated, almost necessitates special software, interacting with the car via the OBDII. There are work arounds, that might avoid that. But...

 

As far as I know, the passivates containing hexavalent chromium all got the heave-ho; if you look on my caliper-finish thread at the list of Toyota plating standards I found somewhere, you can see where the 6500G standards were obsoleted by 6524G standards that are all "hexavalent chrome free". But even so, you can see that with the right materials scientists on the case, the new standards still beat the old ones on the salt spray test.

Then for grins you can glance down at the 6530G zinc-nickel alloy plating standards, which blow any plain-zinc salt spray numbers completely out of the water.

Unfortunately, the local plater in my town still hasn't ventured into ZnNi.

-Chap

 

The trouble is just that when you buy a (non-Toyota) reman from your friendly chain auto store, you're getting something that

1. was once a real Toyota caliper (probably)
   
2. has had all the original Toyota-standard plating sandblasted off
3. then got dunked in some coating that keeps real nice in the box and up until your first rainstorm.

-Chap

 

Where bleeding the Prius gets complicated is if there's been air admitted into the fiddly stuff up front (ABS actuator, master cylinder, accumulator and pump). Provided you make sure to avoid that (keep that reservoir from getting low!), bleeding a line out to a caliper doesn't end up much different from the old shade tree days. It's a little easier, even, when instead of having to pump the pedal over and over, you just hold it and watch the pressurized fluid stream out (making sure not to let the reservoir get low...).

-Chap

 

How about for pushing a piston back in: would you risk cracking the bleed screw? Or is that not really needed anyway? In past Ive just pushed pistons back in, left the bleed screw shut. Not sure either way.

Also, I've got a Mighty Vac, have yet to use it. (Really, I take the prize for over prepared and under utilized, lol.) Would hooking that up to the bleed screw help when you crack it.

 

Good news. How did it do swapping brake line over, bleeding air? Any problems?

Do heed my caution about the piston face cross pattern, pin, and so on. A simple check that it's seated properly: raise the rear again and check turning resistance, compare side-to-side.

 

More inconveniently, I was looking in the parts catalog at Village Toyota, and if the illustrations are right (they usually are), the rebuild kit that you can order includes the piston seals and boots and guide pin boots and grease, but not the seals for the parking brake shaft entry ... so if it leaks there, it seems not to be field-rebuildable, unless you have your own source for seals of the right size and material.

-Chap

 

I know this thread is years old, but I found it because I have the same issue. It's coming from the bolt with the red arrow that Mendel Leisk posted. If anyone reads this, is there any chance an issue like this could cause a " check hybrid system" to come up on the dash? Or would that likely be a separate issue? My Prius may be on its way out (220,000mi) if it just needs a caliper, no big deal. If it needs a new hybrid battery, then it's time to throw in the towel, because I'm about to switch jobs and was going to move up to a truck anyways..but if I can squeeze a few more months out of it with just a caliper then I will. I had a code p0a80, then cleaned the entire battery vent system and it stayed off for a while. I'm going to have the code checked again tomorrow.. was just wondering if a brake issue could also trigger "check hybrid system"