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Discussion Starter #1
pistons won't budge, feels like theyre seized. i suppose i could take a rubber mallet to them but before i do that, any suggestions?

oh yea, the brakes are not on the car, no brake fluid in them. completely dry.
 

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First the basics. Is this a front or rear caliper?

How long have they been off the car? Are they truely dry? If so, the seal itself may just be dry and sticking. Or air/moisture could have gotten in, caused corrosion, and made the piston stick.

What tools (if any) are you using to compress the piston? I've used a "C" clamp before to move really stubborn pistons. They also make specific caliper piston tools for compressing the piston.

Since the caliper is off the car you could try spraying silicone lubricant (or some other seal-safe lubricant, nothing petrolium based) into the caliper to help it move easier.
 

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Discussion Starter #3
hi bigT

they are front brakes from an Si coupe. got them here last December so they've been sitting in a box in my basement since then but I don't know if the previous owner had used them or if he also had them sitting around for a while. I just know everything has just been pretty muh dirty with brake dust and pretty dry overall

The pistons are compressed all the way so j actually need to pull them out. I can spray silicone grease from where the brake line screws in and it won't cause any issues with the internals?
 

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The light silicone lubricant spray should be fine.

Is it possible to mount them on the car and simply pump the brakes to get them to come out? Do you need to remove the pistons completely from the calipers?
 

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I guess a better way to word what I said above is: If it's possible to mount them on the car (really just connect the brake line) you can pump the brake pedal to get them to come out. However, if you want to remove the pistons completely, this is a messy way to do it (because they will be full of brake fluid afterwards).
 

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yea I want to remove them completly so I can send them off for powdercoating. do you think compressed air instead of pumping in brake fluid would help and not damage anything?
 

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yea I want to remove them completly so I can send them off for powdercoating. do you think compressed air instead of pumping in brake fluid would help and not damage anything?
Absolutely. Like I said, if you need to remove them compeletly, the brake fluid would be quite messy.

My suggestion for removing them completely is compressed air. Put a piece of wood or something in front of the piston so the piston doesn't bang directly into the caliper. Shoot a little compressed air into the brake hose hole and the piston should pop out. Just be careful not to get any fingers in front of the piston, and don't try to catch it with your hand.
 

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Just curious, why go through all that effort to powder coat them, and do you really have to take the piston out to do that anyway? I assume the heat will damage it?

Hell, I'd just paint the darn things like most other people.
 

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Discussion Starter #10
thanks for the help BigT. I'll try it this weekend.

yea I want them removed for powdercoating because previous ownr had painted them red then tried to grind off the paint but there still some left over. the company will sand blast them before powdercoating that's why they requested that I remove the pistons and seals then cover the fluid compartmet.

anyway. yea. diff strokes for diff folks indeed :)
 

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Discussion Starter #11
BigT! thanks again homie. I sprayed some silicon lube in there, let it sit for a couple nights and then screwed on the brake lines. Used a can of compressed air which straw fit nicely into the light. That pretty much did it. It didn't come out flying thankfully.

Anyone else trying to do this, dont go all out on the compressed air. Just squeeze little bit at a time and you'll see the piston slide out nice and easy :thumb:
 

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No problem, glad it worked out.

I just mentioned the wood and finger caution because I've seen where people either just blow a ton of pressure in all at once (often from an air compressor hose), or sometimes the piston sticks until pressure builds up a bit, then lets go. In either of those situations it can pop out with a decent amount of force. Just don't want somebody to see this thread and smash their fingers trying this. Better safe than sorry :thumb:.
 

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Discussion Starter #13
indeed! take caution everyone! I had jammed some cloth in there just as insurance. next step. tape up holes and send in for powdercoating :biggrin:
 

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^ Good to see you got it done... incidentally, how does the piston cavity look? Is there any corrosion, or was the piston just binding? If there's any corrosion in there, I'd deal with it before you send them out for coating so that you can limit handling once you get them back.

Also for putting the piston back in, you have to put the boot on first, then widen the opening of the boot so you can slip the piston in, then as the piston goes back in, just make sure the boot slips into the groove around the pad seating surface. Also, give the boot a quick lube with a LIGHT layer of lithium/EP grease before you put it back on, just to help keep the rubber soft (rubber dries out as it ages).
 

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Discussion Starter #15
Yes. Seems like it just sat there too long and dried itself into place causing it to bind. It didn't take much for it to come out once it came loose though. There is some sort of corrosion in the cavity. It's still smooth but its a sort of discoloration. It's at the same spot no both calipers. I'll take pics.

What would you suggest I do with it to clean it up? Thanks for the tep on the rubber boot. Do you think silicone grease would work?
 

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Yup, I put just a touch of lube on the seal and boot, just to keep the rubber in good condition and to make sure that everything could slide easily on re-installation.

As for the discoloration, try some vinegar on a Q-tip. If it's a mineral deposit from some moisture that got in then evaporated, the vinegar should help get rid of it since it's an acid. I used vinegar to get rid of any calcium deposits after I ran the calipers through the dishwasher (pre-powdercoat cleaning).
 

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Discussion Starter #17
ok, so I did the vinegar thing after thoroughly cleaning the cavity (didn't put it in the dishwasher though) and it didn't really help much. If anything it turned the spots into an orange-ish colour... like rust, lol. Sprayed on some lube on there to keep the surface rust away for now.

Here are some pics of the vinegar treated cavity:








and this the other one. Haven't touched this one with vinegar but wiped down the cavity dry:








its still smooth but damn, that looks bad lol
 

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Six eyes
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Yeah I think you're alright. If it's still smooth and the piston still moves freely, then I think it's just staining on the metal.
 
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