RTH — Stubborn Brake Piston (1 Viewer)

[jaymar]

Changing brake pads, still on the first wheel, got the Pistons down on one side using channel locks. That didn’t cut it on the other side, short prybar took care of one piston. The other piston isn’t moving. Not nearly enough anyway. I don’t want to damage the brake assembly with a prybar And too much force. I emptied most of the fluid reservoir. I have not opened the bleeder, nor do I want to. Any suggestions on this?

 

[fourtrax]

piston finish is probably de-laminating and corroded causing it to get stuck. replace or rebuild caliper if it were me.

brake fluid (is hygroscopic) attracts moisture and you need to replace the fluid every 3-4 years to keep the system working correctly. when you use your brake any moisture /dirt in the system is pushed to the calibers. if you dont bleed them the moisture will ruin the pistons.

 

[Landseer]

If the piston is not moving freely when you try to compress it with channel locks/pry bar it's not going to move freely when driving either. The caliper needs to be either rebuilt or replaced, rebuild kits are cheap and rebuilt calipers are not too expensive either. If you really need to get it on the road now you can pull the caliper off the rotor and stack the old and new brake pads in the caliper. Then use the pistons on the good side to compress the bad piston. If you turn on the engine while doing this be sure the E-brake is on and transmission is in park

 

[jaymar]

These are remanufactured brake assemblies. They were new when the last brake pads were put in. That is newly re-manufactured. Felt no brake drag while driving.…

 

[Grandlooser]

Sometimes you can get a bite on the edge with vise grips and rotate the piston it helps a lot. I've also resorted to a few blasts with an air hammer to convince it to move. This is why I don't like to baby my brakes, regular wear keeps Pistons moving.

Also, if you get it free, cycle it in and out a bunch of times.

 

[jaymar]

The worn down pad that came out of there will not fit beside that piston. So not only has the piston not recessed, it’s actually protruded more.

 

[FlashBang]

The worn down pad that came out of there will not fit beside that piston. So not only has the piston not recessed, it’s actually protruded more.

They do that, when push one down it pushes the other out. Local parts store should "rent"/loan you tools to compress it. If that does not work then like the others said it may be time to rebuild. I have sent some stubborn ones back home and they end up working fine. If it worked before it is likely it is not broken, just be sure if you get it back together.

 

[fourtrax]

use a piece of wood or stick a tire tool or large screwdriver in a heavy hose and push against the piston and rotor see if you can get it to move a little.
you could even use the old pad endways to pry the pistons at the same time.


if nothing happens try cracking the bleeder and see if an fluid exits while prying.


once you get the pads in. have someone pump the brake pedal a couple time and hold it down. then very briefly open and close the bleeder valve about 1/5 to 1/4 turn ( fluid will shoot out so don't be in the line of fire). this should let any air out. if brake are soft repeat of get a little bleeder kit like this to make sure no air bubbles.
Amazon product ASIN B000CMDP44

 

[jaymar]

This seems to have happened immediately after I gave up on the channel locks with the other piston, and used the prybar. That pushed the other piston way down. I’m guessing that’s when this piston moved up. Does that tell you anything? What will opening the bleeder valve accomplish? And am I better off doing that or renting a compression tool? I want to avoid air in the lines.

 

[jaymar]

OK so, weirdness. I was just about to wrap it up and call it quits for the moment, when I thought one more try it… So, I tried to pry bar from the other direction, from the front of the vehicle. And the piston went down without much trouble. It didn’t push the other one up either. The rest of the way with channel locks. Any idea why that worked?

 

[FlashBang]

This seems to have happened immediately after I gave up on the channel locks with the other piston, and used the prybar. That pushed the other piston way down. I’m guessing that’s when this piston moved up. Does that tell you anything? What will opening the bleeder valve accomplish? And am I better off doing that or renting a compression tool? I want to avoid air in the lines.

You should bleed them anyway, get the air out, get some fresh brake fluid down there. You should not have to open the bleeder to get the piston to move, the fluid will go back through the lines to the master cylinder. Opening the valve will let you know if you have an obstruction in the lines, something I have never seen. Do you have any c clamps? I have used those to push the cylinders back in?

 

[FlashBang]

OK so, weirdness. I was just about to wrap it up and call it quits for the moment, when I thought one more try it… So, I tried to pry bar from the other direction, from the front of the vehicle. And the piston went down without much trouble. It didn’t push the other one up either. The rest of the way with channel locks. Any idea why that worked?

Weird stuff happens. Just be sure it works when you get it back together.

 

[Grandlooser]

Because the farther out of the bore they are, the easier it is to diagonally jam it in the bore. I was going to make a post telling you to get centered force on it before I read your last post. You likely just put force on one edge and cocked it in the bore. When they are only 1/4 out you can push anywhere you want and they go back in square

 

[jaymar]

Victory! Thank you!
Now for the other side, as darkness falls across the land and the wild beasts come out to play...

 

[jaymar]

Because the farther out of the bore they are, the easier it is to diagonally jam it in the bore. I was going to make a post telling you to get centered force on it before I read your last post. You likely just put force on one edge and cocked it in the bore. When they are only 1/4 out you can push anywhere you want and they go back in square

Makes perfect sense.

 

[Grandlooser]

Now to clean and redo those knuckles.

 

[jaymar]

Before someone points it out, there was no anti-rattle clip.

 

[jaymar]

Now to clean and redo those knuckles.

Sure, come on over. I’ll give you all the beer you want. You supply the parts, right?

 

[Grandlooser]

Sure, come on over. I’ll give you all the beer you want. You supply the parts, right?

Aside from the parts bit it sounded good.

 

[jaymar]

Actually I have the parts, tucked away for a rainy day.…