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Old 05-25-06, 04:29 AM   #1
blue_neon
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Problem - Brake 'piston' popped out of caliper...please help!

I was pumping one of the pistons out of my rear brake Hayes Nine XC to lube it, and i accidently pumped it out too far and i heard a little 'pop' and it seems that the piston came out of the caliper slightly. It didn't fall out, but it wasn't sitting in probably .

Anyway i pushed and pryed it back in with a screw driver, but now the brake dosn't work. I pull the lever and nothing happens. So my number one guess is that there is a lot of air in the system and it needs re-bleeding?

If its only rebleeding then thats fine! I have a bleed kit on its way and i have Dot 4 fluid and i'm ready to go! BUT do you think there could be anything else wrong with it? Since the piston actually technically 'came out' of its placing in the caliper, will re-bleeding just fix it or is there something else...more complicated i need to do .

Thanks!
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Old 05-25-06, 05:52 AM   #2
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I have no experience of this with hayes, but have taken apart shimano hydros before. So long as the piston and housing isn't damaged, it will just need a thorough bleeding.
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Old 05-25-06, 06:09 AM   #3
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Yeh the piston and caliper housing is fine. Looks like i'll just have to wait untill the bleed kit arrives...

Also i think there might be quite a bit of air in there, should i just bleed as normal or is there anything else you recommened i do aswell?

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Old 05-25-06, 07:03 AM   #4
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Quote:
Originally Posted by blue_neon
I was pumping one of the pistons out of my rear brake Hayes Nine XC to lube it, and i accidently pumped it out too far and i heard a little 'pop' and it seems that the piston came out of the caliper slightly. It didn't fall out, but it wasn't sitting in probably .

Anyway i pushed and pryed it back in with a screw driver, but now the brake dosn't work. I pull the lever and nothing happens. So my number one guess is that there is a lot of air in the system and it needs re-bleeding?

If its only rebleeding then thats fine! I have a bleed kit on its way and i have Dot 4 fluid and i'm ready to go! BUT do you think there could be anything else wrong with it? Since the piston actually technically 'came out' of its placing in the caliper, will re-bleeding just fix it or is there something else...more complicated i need to do .

Thanks!
i am not sure in what manner you used a screw driver...but next time, please don't use a screw driver and come ask the forum for help first. did you really think that the screw driver idea was a good one??? that made me cringe reading your post...

yes, you could have cause burrs in either of the metal surfaces. i would pop it back out and check everything. not trying to make you feel bad, but how do you know you didn't compromise the O-ring seal??? it would be worth the investigation now before you spend the time bleeding it and find out there was more to it after words.

just a good bleeding should be fine. the calipers are meant to let air bubbles rise to the bleeder valve. however, to facilitate air movement, you can heat the caliper with a hair dryer or heat gun (NOT A TORCH) and tap on the caliper with like something plastic or wood (NOT A SLEDGE HAMMER) and this should help "break" away any stuck bubbles.

also, if you take the piston back out to inspect things as i suggest, you could top off the opening with brake fluid before you push the piston in and allow the fluid to over flow a little and you might actually get away with barely even needing a bleed.

i would check to make sure there are no burrs on either the caliper bore or the piston. if there are, remove them. also make sure there are no slices in the o-ring seal. if there are, replace it.

you should be okay in the end though

Last edited by mx_599; 05-25-06 at 07:18 AM.
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Old 05-25-06, 07:26 AM   #5
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since you have to re-bleed anyway you might want to take it apart to have a look at the piston and O ring to see if you caused any damage. And don't worry too much, a screwdriver is fine for pushing pistons back in as long as you are careful and don't push on the center post.
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Old 05-25-06, 07:39 AM   #6
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Originally Posted by vw addict
since you have to re-bleed anyway you might want to take it apart to have a look at the piston and O ring to see if you caused any damage. And don't worry too much, a screwdriver is fine for pushing pistons back in as long as you are careful and don't push on the center post.
yes, sorry if i sounded like a jerk above. using a screwdriver to pry pistons back in is fine when you use it against the brake pad. i was envisioning you using the screwdriver in other horrid ways....
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Old 05-25-06, 04:27 PM   #7
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Ahh i really dont want to take it apart, i'm not very confident. I'm not sure why i would have 'busted' the o-ring. The piston didn't fall out, its just went far enough that it wasn't seated problaby and i CAREFULLY pryed the EDGES of the piston from 3 different spots back in.

Without the bike in, and when i squeeze the lever, the piston actually moves! It moves out, but a bit slower, but it dosn't have the 'power' to clamp the rotor when the wheel in.

Is this a syptom of air? Also i really dont think there is any problem/damage at all to the piston or caliper but i will have a look tonight. Infact i'll dismount brake from the bike to get a better look. I'm not even sure how to take apart the brake and problaby take the piston out anyway so i'll think i'll leave that for now.

MX- If i took the brake/house/lever off, and somehow tied the lever end up really high, and the caliper was down low, then did the 'heating' method could this help get the air up better then if it was still on the bike?

Thanks
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Old 05-25-06, 04:31 PM   #8
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Quote:
Originally Posted by mx_599


i would check to make sure there are no burrs on either the caliper bore or the piston. if there are, remove them. also make sure there are no slices in the o-ring seal. if there are, replace it.
I dont even know where the o-ring seal is located , and how do i reconise a burr?
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Old 05-25-06, 09:44 PM   #9
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i saw the same thing in my head imagining a screw driver against piston, i had thoughts of the time i witnesed my friend using needle nose pliers on nuts, i about had a heart attack
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Old 05-26-06, 04:49 AM   #10
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The o-ring seal sits between the body of the caliper and the piston; you will not be able to see it without taking the thing apart. Like you say it's pretty unlikely that you damaged it, so I'd just leave it. When the piston is in its out (but not popped out of the caliper) position you can check the sides for scratches and small shards of metal (burrs) that could potentially damage the seal.

From your description it sound like your brake is ok though, just keep bleeding it any eventually it'll spring into life again.
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Old 05-26-06, 05:17 AM   #11
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Ahh I see, thanks for the replies everyone .

I've tried all i can (even heating it up with the hair drier and tapping/letting the air try to rise up the hose), but still no luck so i will just be waiting untill my bleed kit arrives.

A question on bleeding with the Hayes system, i understand how to connect it and bleed it down at the caliper, but at the master cylinder i'm not sure where the fluid actually escapes? There are two weird nuts, that are like an octogan screwdriver thread inside, but there is also a little plastic 'knob' about 3mm in diatmeter...i assume thats the end where the fluid escapes from whilst bleeding?

How should i remove this correctly then re-install it after wards?

Thanks again
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Old 05-26-06, 05:50 AM   #12
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Also if there was a 'crack' or damaged o-ring or something, wouldn't there be fluid leaking?

Cheers
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Old 05-26-06, 06:37 AM   #13
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Why would you get yourself into this in the first place?

Why lube it?
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Old 05-26-06, 08:16 AM   #14
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Originally Posted by chelboed
Why would you get yourself into this in the first place?

Why lube it?
You need to "lube" the piston with DOT 4 when it gets stuck and won't move. Otherwise the rotor will rub, and if you recenter them without fixing the stuck piston the rotor will usually rub on the caliper body. You see this alot in dry dusty conditions.
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Old 05-26-06, 08:46 AM   #15
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Originally Posted by blue_neon
Also if there was a 'crack' or damaged o-ring or something, wouldn't there be fluid leaking?

Cheers
Yes, if the seal, piston, or cylinder is damaged enough it will leak fluid. You have air in the lines.. bleed the brakes.
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Old 05-26-06, 08:55 AM   #16
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Quote:
Originally Posted by vw addict
You need to "lube" the piston with DOT 4 when it gets stuck and won't move. Otherwise the rotor will rub, and if you recenter them without fixing the stuck piston the rotor will usually rub on the caliper body. You see this alot in dry dusty conditions.

Good tip, I didn't know that.
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Old 05-26-06, 11:06 AM   #17
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Quote:
Originally Posted by Evilbee
The o-ring seal sits between the body of the caliper and the piston; you will not be able to see it without taking the thing apart. Like you say it's pretty unlikely that you damaged it, so I'd just leave it. When the piston is in its out (but not popped out of the caliper) position you can check the sides for scratches and small shards of metal (burrs) that could potentially damage the seal.

From your description it sound like your brake is ok though, just keep bleeding it any eventually it'll spring into life again.
yeah i agree....sorry i was studying yesterday. it doesn't sound like you did anything bad as i first thought. just do a good bleed, don't stress too much about tapping or heating or postion of the setup at this point. just mount it and bleed. sorry if i misled you.

next time though, always pry against the pad not the piston. you can't hurt the pads but pistons are finely machined parts
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Old 05-26-06, 11:08 AM   #18
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Originally Posted by blue_neon
Also if there was a 'crack' or damaged o-ring or something, wouldn't there be fluid leaking?

Cheers
doesn't have to leak right away. it could take awhile for the burr to wear into the o-ring.

but don't worry about it, i don't think you gouged anything
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Old 05-27-06, 01:27 AM   #19
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Thanks . I'll try a good bleed when the kit arrives. If i still have problems i'll post back, if it seems the piston/any is damaged and can aquire a new o-ring and piston for about $30AUD...i guess i'll just have to wait and find out!

Thanks again
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