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Suspension & Braking
Have some questions about suspension or brake setups for your E46 BMW? Get all your answers here!

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Old 02-02-2013, 08:55 PM   #1
chillinhardinanE46
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Caliper piston pushed out and now wont go back in

Like the title says, the brake caliper piston was pushed out via brakes in an attempt to lower the fluid in the brake resivor while helping a freind do his brakes. The fluid level lowered but now the caliper wont budge when using a c clamp. How can we get it back in?

I read around breifly and some people reccomended opening the bleeder screw. Im not sure if that would help and I dont want to open it to no avail. Any one have any suggestions as to why it might not go back in? MAybe push it out again and try pushing it in the the c clamp? or open bleeder valve?
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Old 02-02-2013, 09:02 PM   #2
R. Cate
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If you guys are working on the pistons in the rear brakes, I'm almost certain that they need to be rotated back in place. You'll see two little notches on the piston.
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Old 02-02-2013, 09:04 PM   #3
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For one, remove reservoir cap and try gently to push it back. It might be hung up on the square o-ring in the caliper...might be because the seal was broken and the piston is rusted at the bottom. It's not used to coming out that far.

Try my idea first and go slowly and evenly. Maybe compress with old pad on and a c-clamp.

In any case, a remanned caliper is guaranteed to work and simplest if you need...and if you get this one back in, tell buddy to monitor his rotor temps and brake fluid level to ensure he doesn't have a leak and that his caliper isn't seized and holding pad onto rotor.

GL...and a bump for other ideas for you!
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Old 02-02-2013, 09:37 PM   #4
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Quote:
Originally Posted by chillinhardinanE46 View Post
Like the title says, the brake caliper piston was pushed out via brakes in an attempt to lower the fluid in the brake resivor while helping a freind do his brakes. The fluid level lowered but now the caliper wont budge when using a c clamp. How can we get it back in?

I read around breifly and some people reccomended opening the bleeder screw. Im not sure if that would help and I dont want to open it to no avail. Any one have any suggestions as to why it might not go back in? MAybe push it out again and try pushing it in the the c clamp? or open bleeder valve?
Advice: next time, lower the level of fluid in the reservoir with a clean turkey baster.

The fluid behind the piston is under pressure. Why fight it? Open the bleeder screw one turn or so (with a drain hose on it to catch fluid). You're going to be adding a little fluid anyway and the fluid behind the piston is the dirtiest in the system. Bleed that stuff out.

Press the piston back in with your thumbs, wobbling the top of the piston and going slowly. At first, nothing will move, but then fluid will start coming out of the bleeder screw, the piston will sink flush against the bottom of the caliper cylinder, and all will be well with the world. Tighten bleeder screw, install pads. Add some fluid to the res before pressing the brake pedal. You don't want to let the res get too low and allow air into the master cylinder.
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Old 02-02-2013, 10:24 PM   #5
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Originally Posted by R. Cate View Post
If you guys are working on the pistons in the rear brakes, I'm almost certain that they need to be rotated back in place. You'll see two little notches on the piston.
This is only necessary on cars with integrated rear disk parking brakes. Our cars have a separate parking drum brake built into the hub of the rear disk - no winding needed.

Luke
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Old 02-02-2013, 10:30 PM   #6
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Originally Posted by pleiades View Post
Advice: next time, lower the level of fluid in the reservoir with a clean turkey baster.

The fluid behind the piston is under pressure. Why fight it? Open the bleeder screw one turn or so (with a drain hose on it to catch fluid). You're going to be adding a little fluid anyway and the fluid behind the piston is the dirtiest in the system. Bleed that stuff out.

Press the piston back in with your thumbs, wobbling the top of the piston and going slowly. At first, nothing will move, but then fluid will start coming out of the bleeder screw, the piston will sink flush against the bottom of the caliper cylinder, and all will be well with the world. Tighten bleeder screw, install pads. Add some fluid to the res before pressing the brake pedal. You don't want to let the res get too low and allow air into the master cylinder.
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Old 02-02-2013, 10:30 PM   #7
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Originally Posted by chillinhardinanE46 View Post
Like the title says, the brake caliper piston was pushed out via brakes in an attempt to lower the fluid in the brake resivor while helping a freind do his brakes. The fluid level lowered but now the caliper wont budge when using a c clamp. How can we get it back in?

I read around breifly and some people reccomended opening the bleeder screw. Im not sure if that would help and I dont want to open it to no avail. Any one have any suggestions as to why it might not go back in? MAybe push it out again and try pushing it in the the c clamp? or open bleeder valve?
OP - I'm confused. Although pushing the piston out lowers the brake fluid level - pushing it back in will raise it right back. Why did you push the piston out in the first place?

In any event, at this point you can certainly try opening the bleeder. This won't hurt anything - although you'll want to bleed the system when you're done. Dmax is right, if you pushed the piston too far out, then you may have gone past the seal. Or, more likely, you have cocked the piston in the borse slightly. You may need to pull the piston completely to get it to go in straight. At which point - get a reman and call it a day.

Good luck.

Luke
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Old 02-02-2013, 11:05 PM   #8
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A c-clamp or a large pair of channel-lock pliers should push it back in without opening the bleed screw...however, cracking the bleeder is preferable to forcing it if it's stuck.

If the piston is all the way out, you're going to have to relieve all pressure (crack bleeder and likely depress brake pedal/disconnect line from caliper) and get it back in. If you're at that point, a full-on rebuild is your best course of action.

Not sure what you were trying to accomplish. The best way to lower the fluid level in the reservoir is the crack a bleeder and let the excess fluid out. A little-known factoid is that BMWs with ABS can be one-man bled without much fuss--the valves in the ABS unit act as check valves, so crack a bleeder and pump the pedal. As long as you don't suck air in the reservoir (watch your level closely), you can bleed all 4 corners by yourself, just by pumping the pedal. Have a hose on the bleeder nipple and something to catch the fluid that spurts out, obviously. Gravity bleed works as well.
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Old 02-02-2013, 11:09 PM   #9
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Originally Posted by dmax View Post
For one, remove reservoir cap and try gently to push it back. It might be hung up on the square o-ring in the caliper...might be because the seal was broken and the piston is rusted at the bottom. It's not used to coming out that far.

Try my idea first and go slowly and evenly. Maybe compress with old pad on and a c-clamp.

In any case, a remanned caliper is guaranteed to work and simplest if you need...and if you get this one back in, tell buddy to monitor his rotor temps and brake fluid level to ensure he doesn't have a leak and that his caliper isn't seized and holding pad onto rotor.

GL...and a bump for other ideas for you!
I just replaced my front calipers today. I bought 2 front reman calipers from Pep Boys with a coupon, $70 for both. Great recommendation Dmax. I took off the cap for the brake fluid reservoir and squeezed the piston down with a big ass pair of pliers. All went great until I got it all back together and the brake pedal went to the floor. Back to Pep Boys with a ride from the wife and bought a cheap bleed kit for $8.99 and did a quick bleed for air that got trapped when replacing the caliper, with the help of my son.
By the way, the calipers were actual BMW calipers just reman in Mexico. IMO, a great, inexpensive option.
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Old 02-02-2013, 11:12 PM   #10
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Originally Posted by lmr2wil View Post
This is only necessary on cars with integrated rear disk parking brakes. Our cars have a separate parking drum brake built into the hub of the rear disk - no winding needed.

Luke
Thank you for the clarification on that.


Rex
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Old 02-02-2013, 11:21 PM   #11
chillinhardinanE46
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Thanks for the quick replies guys.

The problem was the piston had come out and wasnt seated correctly. It seems like nothing was damaged. How should he monitor rotor temps? Like an infrared temp gun or somthing like that?

Since I didnt want to get air in the system I told him to push the breaks to push the piston out a bit and i was able to get it in correctly with my hands. then it went back in super easy.


as we were taking off there was a clunking sound coming from that tire.

I told him not to drive. I was puzzled since we put everything back on right.

turns out he forgot to tighten the bolts holding the wheel.
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Old 02-02-2013, 11:32 PM   #12
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brakes

and scary listening to stories like this and knowing there are cars out on the roads with problems like these and worse
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Old 02-02-2013, 11:44 PM   #13
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Originally Posted by chillinhardinanE46 View Post
How should he monitor rotor temps? Like an infrared temp gun or somthing like that?
Why would he need to?
Quote:
Since I didnt want to get air in the system I told him to push the breaks to push the piston out a bit
You should stop giving him advice. Also, spelling is ftw.
Quote:
i was able to get it in correctly with my hands. then it went back in super easy.
He probably has air in the system now. Bleed that line, if not all of them.
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Old 02-03-2013, 01:46 AM   #14
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C clamps and Chanel locks re not the best tool for this job. It is too easy to get the cylinder cocked, and screw up the bore. Get a real set of caliper piston compressors from Harbor Freight. They are $35, and you can find a 20% off coupon just about anywhere. It will also work on any car or truck you may have, even those that have to be screwed back in. Use the right tool for the job.
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Old 02-03-2013, 07:22 AM   #15
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Unbelievable.
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Old 02-10-2013, 09:51 AM   #16
chillinhardinanE46
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this guy


Quote:
Originally Posted by lcoleman View Post
Why would he need to?

If the caliper was damaged in any way, there is a possibility of a stuck caliper, which could cause the rotor heat up due to being in contact with the pad. Just a thought.


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Originally Posted by lcoleman View Post
You should stop giving him advice. Also, spelling is ftw.
My spelling is Fantastic Terrific and Wonderful? Why thank you
I though this was E46FANATICS forum..I hope you dont think that means english fanatics from room 46 cuz your in the wrong forum


Remember that any idiot can use a computer and spell check.
I was on my phone and had mechanics gloves on. I had no idea my grammar would bother fellow fanatics that much. Sorry bro. Next time ill ask my buddy to let me use his laptop.

My advice was for him to stop what he was doing and ask the fanatics...(which I did for him since he is not on the forums)


Let me give you some advice. Take a chill pill every day in the morning when you wake up.

Relaxing is good for you.

Quote:
Originally Posted by lcoleman View Post
He probably has air in the system now. Bleed that line, if not all of them.
Friend states the pedal feels better, no "softening"

Thanks to everyone else for your posts.

DISCLAIMER** No calipers were hurt in the making of this post**
(I dont want lcoleman to worry too much.. Just trying to help a fanatic out)
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Old 02-10-2013, 09:58 AM   #17
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..repost..

Last edited by chillinhardinanE46; 02-10-2013 at 10:00 AM.
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