Front brake caliper piston won't compress?! (2 Viewers)

[LXGus]

Working on a break pad and rotor swap and this piston won't compress. Does anyone have thoughts on how to resolve this? Was the piston pushed too far out of It's track? Thanks!

 

[gaijin]

Working on a break pad and caliper swap and this piston won't compress. Does anyone have thoughts on how to resolve this? Was the piston pushed too far out of It's track? Thanks!

View attachment 2983269

If you're swapping out the calipers, why worry about it?

Or do you mean a pad and rotor swap?

 

[LXGus]

If you're swapping out the calipers, why worry about it?

Or do you mean a pad and rotor swap?

I updated my post - I'm doing a pad and rotor swap - not calipers. So the new rotors and pads won't fit into the caliper without fully compressing the piston.

 

[aztoyman]

I usually use a bar or screwdriver as a lever to push them back in. I have had to use a C-clamp on stubborn ones. But if it doesn't move freely after that it's time for rebuild or replacement. Good luck.

 

[doru]

How did you try to compress them? You cannot push them out too far. If you push them out too far they will just come out of the caliper - messy job to put them back in.

 

[bigredmachine]

i like leaving the pads in the caliper and using two big screwdrivers between the pads and rotor to push the caliper pistons back in. for the one that isnt going in your probably going to need a caliper but you can take a pair of slip joint pliers and try to get the one piston to move.

 

[supercarrera]

Did you try releasing the bleeder valve? A lot of times you need to do that to be able to compress the piston. Just loosen it until brake fluid starts dripping out.

 

[LXGus]

How did you try to compress them? You cannot push them out too far. If you push them out too far they will just come out of the caliper - messy job to put them back in.

How do you get them back in?

 

[LXGus]

Did you try releasing the bleeder valve? A lot of times you need to do that to be able to compress the piston. Just loosen it until brake fluid starts dripping out.

I’ll give that a try. The other three were easy to move so not sure if that would still be the issue?

How did you try to compress them? You cannot push them out too far. If you push them out too far they will just come out of the caliper - messy job to put them back in.

I have a feeling that’s what happened. I used a ratcheting tool that broke after about two minutes of use on the first tire so I’ve been using the metal plates from that tool to sort of manually slowly pry the pistons apart.

 

[Docwyte]

I've got a tool that I use, it compresses both old brake pads up against the pistons to retract them. Without the tool I'd reinstall the old brake pads and use a large flat head screwdriver to lever the pads against the pistons to retract them, Before you do that remove the cap from the brake fluid reservoir. I wouldn't loosen the brake bleeders themselves.

 

[bigredmachine]

I have a feeling that’s what happened.

thats not what happen, you would have had to have the brakes grinding for a very long time to the point that you were actively ignoring it. when the pistons pop out you will see brake fluid leaking out from the caliper.

the ratcheting tool should push all 4 pistons in at the same time so one piston wont pop out when their all getting compressed

 

[Sandroad]

Hmm....it looks like you got 3 of the 4 to move back. I wonder if when you pushed the others in that one came out too far and is now stuck on the back side of the piston? It looks really close to the rotor. It's also not uncommon for pistons to get frozen in calipers from corrosion. If that' the case, it's new caliper time anyway. Any unusual wear on the pads that would indicate a stuck piston?

 

[doru]

Here is how you deal with removing the piston...
Keep in mind that this is considered a semi-rebuilt. You will need brake fluid to flush the lines after as you'll be getting air in. At that point you might as well remove the caliper and work on it on a bench. If you remove the caliper you need new a crush washers for the banjo bolt.

You may need a new piston seal and a new piston boot if you damage them, or just cause it is best practice for peace of mind - high probability you will damage them if you never done this before.

First you clean very, very well the area around the piston!
Next find a way to block the other pistons from coming out - a block of wood for the two of them and a clamp for the one opposite the one you want to remove.
Use compressed air on the banjo port to push the piston out. Watch your fingers when the piston comes out!
If you do not have compressed air - use a flat screwdriver to pray the piston out using the grove that the boot is sitting on. Try not too damage the boot!
Once the piston is out, remove the boot from the bore using a flat screwdriver.
Clean the piston and the piston bore.
There is a rubber seal inside the bore wall you may also want to remove for inspection.
Inspect the cause of the failure: piston, bore, seal. See how the surfaces look like. After removing the seal lube the piston and bore with brake fluid and try to see it the piston slides inside the bore without the seal. If it does not then you may need a new piston or a new caliper. If it does then you can reassembly it. I recommend using a new seal.

Search Youtube, there are lots of videos how to do it.

 

[rrc swb]

Gus,

I'm not a mechanic, nor I slept at the Holiday Inn Express last night... But I just finished doing the brakes on my car and that's one of the things I noticed.

The pistons may have corrosion and that's why they are not sliding back easily.

If you open the bleeder valve you'll release the pressure and the piston should go back in while you are compressing. Put rags on the floor and near the brake, it'll get messy.

Hope this helps you out.

BTW... I use this Chinamade Special tool

Amazon product ASIN B08LY4NCHG

 

[NYC570]

I use a C clamp with a piece of wood to retract the pistons. If the piston is that stuck, there might be a tear in the boot and it might have sized. If this is the case, you don't need to replace the caliper but rebuild it. It's fairly straight forward and much cheaper. Toyota sells the rebuild kits and pistons if there's damage upon inspection.

 

[Sandroad]

Keep in mind a new OEM front caliper is only about $160 on line.

 

[Sandroad]

I use a C clamp with a piece of wood to retract the pistons. If the piston is that stuck, there might be a tear in the boot and it might have sized. If this is the case, you don't need to replace the caliper but rebuild it. It's fairly straight forward and much cheaper. Toyota sells the rebuild kits and pistons if there's damage upon inspection.

Link to a Toyota OEM rebuild kit? Aftermarket is all I could find.

 

[warm fuzzies]

+1 to an old brake pad (or wood) and a c-clamp.

Don’t overthink it — just use mechanical advantage

 

[NYC570]

Link to a Toyota OEM rebuild kit? Aftermarket is all I could find.

I belive 0447860070 is the part number for the front kit. You can get it for a decent price if you shop around.

 

[bloc]

I’ll struggle with explaining this in a way that makes any sense at all but figure it’s worth a shot.

If you pry on one edge of the piston you are trying to tilt it in the bore, and this can cause it to bind. The more extended it is, the less overlap there is between the bore and the sides of the piston, so the more tilt is allowed, and therefore the more bind.

You would be well served to find a way to push at the center of the piston, but the face of it is hollow.. the way I have done this since my toyota pickup days is put a screwdriver across the open face of the piston at a 45 degree angle from a radial line outward from the axle to the wheel, then pry between the rotor and the center of the first screwdriver at a 90 degree angle from that screwdriver. This all seems to strike a balance of evening the forces but not letting any screwdrivers slip.

At issue is your lack of space between the piston and rotor. You may need to allow the rotor to tilt away from the piston you are working on.. if it is corroded/bonded to the hub face loosen it up with a dead-blow hammer, leave the caliper in place. That should give you more room between the rotor and piston face to work.

Hmm....it looks like you got 3 of the 4 to move back. I wonder if when you pushed the others in that one came out too far and is now stuck on the back side of the piston? It looks really close to the rotor.

This could also be the case. But, our brakes are designed to keep the pistons well in place even when the brakes are worn down to just the backing material, which is quite thin. I personally don’t think the piston is out too far, yet.. though it may have pushed further than the others increasing the odds of tilting and binding.


It’s good our calipers and pistons are steel.. that fact gives you some protection against forcing a piston that is binding from damaging the bore. @LXGus I’m pretty sure you don’t need any more parts or to go through the effort of opening and rebuilding anything just yet.. just a change in technique should get this thing moving.

Edit: looking again the rotor slot in the caliper won’t allow the rotor to tilt. Try prying evenly on two sides of the piston with flat head screwdrivers and see whether it will move. Just attempt to make them as close to 180° apart and the prying forces as even as possible.