Seized calipers?

[Estima]

Hi all,

I just finished the front passenger (struts, rotor, and brake hose) and bled the brakes. Tested the brakes (drove back & forth and around the block)and went fine. Went over the driver side, jack it up and can`t turn the front driver wheel.

Removed the brake pads and the rotor starts to turn (by hand). I compressed the caliper and it went in to its normal position.

IMG_2593.jpg

I haven`t open up the caliper but suspect the caliper is seized. Can you confirm this? Appreciate your feedback with some advice.

P.S. If I ended up overhauling my calipers, what are the part numbers for those? (93 previa, no ABS, with rear discs).

Thanks!

[TheMAN]

check the slider pins... it's common for them to seize
use only silicone based grease to lube them... most people don't know this and use petroleum based grease which gets baked in and causes the seizing!

[Estima]

check the slider pins... it's common for them to seize
use only silicone based grease to lube them... most people don't know this and use petroleum based grease which gets baked in and causes the seizing!

I tried pulling the caliper and the slider pin slides fine...but I guess it needs de-greasing (who know when it was last looked at )..

What good silicone grease can you recommend?

[TheMAN]

I normally just use 3M silicone paste... not cheap but not too expensive... comes with a brush in the lid... it is a dielectric grease
the stuff toyota uses can be had but is way more expensive... it doesn't justify the cost... I've used the 3M for years and it worked fine

[scottamann]

I tried pulling the caliper and the slider pin slides fine...but I guess it needs de-greasing (who know when it was last looked at )..

This is late, but I had the same problem on my 93'. Turns out that the interior of the caliper was coming apart and there was so much gunk in there that even though I got it to move, it seized a little while later. I just replaced them instead of rebuilding (course, I had a parts van to help, so.. ymmv.)

[pdgizwiz]

I haven't had this issue with a Toyota caliper (yet) but saw it a lot on European cars I've had with Ate calipers. I expect the issue is similar. The piston is sealed to the bore of the caliper with a rubber ring. When the pedal is depressed the space behind the piston is pressurized, and it moves the piston just enough to press the pads against the disk. The rubber ring flexes when this happens, but it doesn't slide in the bore. When the pressure is released, the resilience of the rubber ring pulls the piston back just enough to take take the pressure off of the disk. The actual movement of the piston is slight, but it must be free to move. The rubber ring only slides in the bore as the pad wears as a way to compensate for the lost material.

When crud builds up between the bore of the caliper and the piston to the point where the friction needed to retract it is greater than what the resilience of the rubber ring can overcome, the pad stays in contact with the disk, causing it to drag. You may or may not notice the drag while driving, but it will cause the pads to wear out faster at the very least, and can cause the disk to overheat and warp, or make the van pull to one side or another. Caliper replacement is the safest and easiest course of action if sticking pistons are confirmed.

[dirk005]

I second that on the silicone. Silicone is awesome in comparison to the other stuff. The silicone will defintely help when trying to get yur brakes to work properly.


my brakes were uneven in brake wear. one side was new and the other was close to finish. I was told the brake chasis frame known as caliper had to be changed but it was that the brake guide screws and the brake cylinder(wrongly known as piston) needed to be regreased. to do this you need a air compressor to get the cylinder out of the cylinder shaft or bore. once you do that then you need to regrease everything so that they don't seize again and wear down the brake pads.

[Jonny]

This is worth a try for a sticking piston for anyone interested in a cheap, quick and easy no-harm-done type of thing....

Both front brakes have seized on my van within the last 3 years. If it is the piston sticking in the cylinder you may be able to service it with the unit still in the vehicle. It worked on one of mine... has been good for 2 yrs now.

Remove the pads, disk and the piston boot (there's a hidden spring clip down there in the outer folds of the boot which you can carefully pop out). My boot was torn which is likely why it got all rusty in there. Push the piston out a little with the brake pedal so you expose a bit of extra piston - make sure you don't go too far and pop the whole thing out or you'll have a right mess on your hands. Make a mental note or measure how far out it is... you'll be pushing it out again later. Carefully clean the exposed portion of the piston really well using brake fluid and very! fine (1500 or higher) emory paper if you need to for any rusting. You do not want to scratch this surface. Lube the piston with brake fluid and push it all the way in with a beefy G clamp, or leverage from a big screwdriver or something, keeping an eye on the reservoir and making sure you remove fluid from it if it looks like it'll overflow (more mess if you don't do this). Push the piston back out again to where it was before. The brake fluid you just put on the piston will probably be dirty with rust again. Clean it and repeat. If you're lucky, after a few cycles (took 4 or 5 for mine) the piston will move more freely and the fluid won't be carrying rust.

If it seems to work make sure you check the wheel for heat fairly frequently at first just to make sure everything is still OK.

[tbkilb01]

I tried pulling the caliper and the slider pin slides fine...but I guess it needs de-greasing (who know when it was last looked at )..

What good silicone grease can you recommend?

Antisieze works awesome...

[man_btc]

Additional info:
Brake piston dust boot.jpg

What it can look like if you let your pads wear too thin and the piston over-extends:
Boot_Clip_Comingingout.jpg