Brake Caliper Slide Pin Cleaning and Lubrication

Mendel,
The service manual doesn't show the parking brake cable being in the way . By not removing the caliper (or
even having to flip it up), you don't change the position of the caliper piston. That is why I was wondering why just removing the guide bolts (and leaving the caliper alone) was not sufficient.

 

^ Not sure of how you're picturing, so sorry if this is obvious:

The pins go into long holes in the caliper mounting bracket, then the two caliper ears go over the caps of those pins, then short bolts go through the ears and into threaded holes in the caps of the pins. The caliper has to be out of the way for the pins to come out. With the front you could get the bottom pin out easy enough, without disconnecting the caliper at the top, but still, I see no advantage.

With the rear caliper, it can barely go anywhere without disconnecting the parking cable, but you don't need to bother with that: you can just unbolt top and bottom and flex it back.

 

Mendel,
Ahhh, I was missing the short bolts threading through the caps of the pins. Makes sense now. Thanks.

 

Here's one more pic, showing the (cleaned, lubed and reassembled) rear brake pads. You can see the imprint the caliper piston's cross shape made (left pad). Pretty much explains the correct orientation requirement:


Here's a Repair Manual excerpt on the brakes. It's a bit of a jumble, but there is some info in there if you dig:

 

Mendel,
Reading your links in append #5, it looks like the rear pistons have to be screwed back in and not compressed back in like the front brakes. How hard were they to turn with your bent needle nose pliers ? I was wondering if a new tool was in my future Did you screw them back all the way or just enough to get the calipers back on since you were reusing the old pads ? Thanks

 

There's a tool ref'd on a Prius Brake DIY webpage: Lisle #28600, that should help. It's basically a metal cube with 3/8" drive pockets on each face, and different protrusions on the various faces. I'd direct link the site but my work pc's not letting me access it. Google "paulstravelpictures prius brake" will get you there.

As long as you're reusing pads, you don't need to do any push back of the piston. With the exception: with the rear you do need to rotate the piston to get the cross orientation right.

I'm not clear why that cross gets out of alignment, just pulling it off the disk, but there it is. Every time you step on the park brake cable, it's pulling on a lever arm at the rear caliper, which I believe is rotating a screw inside the caliper cylinder, which is trying to screw itself out of the piston, pushing the piston outward.

I needed to rotate the piston back into proper alignment, about 45 degrees, and opted to turn it clockwise, screwing it back into the caliper slightly.

Then when I had everything re-assembled I did multiple pushed of the brake pedal, to try to repressurize the hydraulics, prior to reconnection of the 12 volt and start up of the car. The object of all this is to avoid upsetting the electronics, getting low pressure warning.

Doing this pedal pushing, I heard a distinct metallic click with each push, for about the first 6 pushes, then nothing for subsequent pushes. I've got to have another look at that lever arm, I'd like to understand better how it's working. But I think there's some sort of adjusting mechanism in it.

Anyway, if and when you're replacing pads on the rear, I think yes, you'd have to screw that piston in completely. I've done this before on another make of car. And I think it would be worthwhile getting the above mentioned tool. There is a fair bit of resistance turning the piston, and the pliers are not the best tool.

BTW, read through the pdf I attached, there's instruction in there.

 

They sell that special tool at any auto store by the way, I've seen it in AutoZone, Pepboys, O'Reilly, Winchester Auto, and Allied Auto.

 

I've done some research on that tool and I've seen conflicting reviews. Some say it is hard to keep the tool against the face of the piston when you are turning it. Others say it is better to go with a kit like this:

The only problem with the kit is how do you know the thread pitch on the screw matches what is on the caliper piston. If it is not the same, the tool won't keep itself pressed against the piston as you turn it, or the tool will apply too much pressure against the piston.
Any suggestions/recommendations on which is a better way to go ? Thanks

 

^ If you could somehow add a flexible washer to the above, some sort of heavy duty spring, to take up the screw pitch variation...

Seems like overkill for the DIY'r , who's needing this very infrequently. Doesn't stop me drooling though.

 

Sadly... I have that kit that is mentioned above lol... still haven't had any use for it just yet. Maybe it'll be used once I do the Prius brakes haha.

 

NutzAboutBolts,
So then, no how to video coming soon huh In the winter around here, the roads get white with salt. I'm wondering how long before the Prius body starts to rust.
There are a few different kits that look pretty much the same. There is one called Astro Pneumatic but they don't list it as working on a Prius. Only a Camry and a Corolla/Celica (and they use two different disc). I can't find the Neiko website to see if they list a Prius. Do you know if it works on a Prius ?
Thanks for your help

 

I'm not sure since I haven't used it yet, but this is the tool I have,
Blue-Point YA8610 - Universal Brake Caliper Tool Kit

It doesn't specify the specific model of the car, it just state that it works on the make of the vehicle such as "Toyota". I would assume it works on the Prius as well.

 

I must be ignorant and lucky. When I did mine I just jacked the car up and did the brake job.
Did not even know you need to disconnect the battery and other protection.
I have done it at least three times because I was trying to locate a clicking sound from under the body.

Now I am not sure if I want to do it again or not...

 

^ If you open drivers door with the 12 volt connected, odds are good the brake system will try to pressurize, and if you've got any of the caliper's away from the disk it could push the piston out.

The other issue: if you push a piston back into it's caliper, to accommodate a new pad, the car may detect low pressure when you turn the car on next time.

I did very minor push back of rear pistons, just to fix the piston head position. I had the 12 volt neg cable disconnected throughout. Before reconnect I pumped the brake pedal repeatedly, and this warded off any problems.

 

Thanks for the info, I confirmed I was lucky. Did not open the driver door.
One question: When you mentioned you had 12-volt disconnected throughout, you meant the 12-v battery in the trunk, right?

Thanks again!

 

I bought that kit several years ago on eBay. I've used it on Cadillac and VW rear disc calipers and the thread pitch really didn't figure in. It makes it a lot easier than using needle nose pliers, which I used to use, too.

 

The little nub on the back of the brake pad keeps the piston from turning, so if the pad is missing, any residual pressure in the lines is slowly going to push it out and it twists as it unscrews.

 

Yes, negative cable disconnected.

 

Here's a document which explains in detail the rear (disc) brake parking brake mechanism:

http://www.autoshop101.com/forms/brake06.pdf