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Discussion Starter · #1 ·
Hello all! I am a new poster, but have been reading the forums for the past year. I just replaced all my rotors and pads (OEM pads/sensors and Centric rotors). All seemed well, until today... the driver rear caliper is possibly frozen :eek:.

My shop said to replace both calipers, rotors, and pads on rear of car. The whole set-up has about 800mi on it. I was hoping to replace just the 'frozen' caliper and de-glaze the rotor and pads, as they are almost brand new (no warping or severe ware).

I am a little apprehensive to break open the system though... I was planning on a bleed in the spring, but am forced to do so now (or pay the shop :tsk:). Does anyone have any advice for replacing a caliper?

From what i have gathered, I should disassemble the driver rear wheel like i did to replace the rotor, get it turned, rough up the pads lightly, remove the brake line and plug it quickly, replace with new caliper and old brake line, reassemble, bleed (DOT 4?), re-bleed, and go. Am I missing something? :dunno:

Sorry if this has been posted, I spent a while trying to find a caliper replacement diy or thread. Nothing very definite beyond a brake line replacement.
 

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Noone Special
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if the system only has 800 miles you may be able to save the rotors. I only say that if the frozen caliper did not wear down the brake pads till it is metal on metal groove the rotor serevely. now the rotor that was on the side of the frozen caliper I would measure the rotor run-out to make sure it wasn't heated up too bad and warped. But since they are new you can have them cut. The pads I would replace because you have uneven wear on one side then the other.
 

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Is it Trackday yet?
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You probably don't need to buy new calipers... you can rebuild the ones you have. Or, you can purchase rebuilt calipers at a greatly reduced price compared to new. I've seen them for about $60ea after core charge is refunded.

The process you outlined is correct. One suggestion that was made to me, I'll make to you... put a layer of plastic wrap over the fluid reservoir fill hole then screw the cap back on. This will almost completely prevent fluid from leaking at the caliper hose while you have it off for replacement. It plugs the breather holes in the cap so a vacuum is created.

Get two liters of fluid so you'll have it on hand should you need to bleed a lot of fluid out. You will probably need to bleed it in the garage and again after driving the car a bit.
 

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catso
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You should be able to rebuild the calipers and reuse your existing pads and rotors unless you see some abnormal wear or scoring. It's an easy DIY. There's a link in the wiki. Make sure you clean up and relube the the guide pins and bushings too. My only question is: why wasn't this problem addressed 800 miles ago when the brakes were done?
 

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Discussion Starter · #6 ·
Thanks for the response and the insight! I will definatly be trying the cellophane trick.

I did clean up and re-grease the slide pins when I did the brakes. I thought that the cylinder was a little stiff, but was working OK. Should have spent more time on it then, instead of now. Car is an '04 and has one record of brakes being flushed in '06. That may have been the last time it was done, so I am flushing this go around as well. lesson learned.

For now I will only be replacing the driver rear caliper, I just got out of college and don't have a lot of money after the rotors, pads, and tires (Michelin Pilot Sport A/S Plus).

I ordered a re-man. caliper and will determine if the brakes are good to use again when the caliper gets in (new slide pins too).

Also, doesn't the Bently manual say not to grease the slide pins? I thought that the grease may have caused the failure. Could this have been caused by the E-brake not being adjusted? I will be doing this as well.

Anyone interested in pics of this job or the rotors?
 

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We want the Lion!
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BMW recommends that slide pins should be polished and installed dry. I always use a really thin smear of high temp brake grease anyway. I've seen too many rusted guide pins to install them dry, even with good boots.

You need to determine why the caliper siezed in the first place. Piston not retracting? Bad seals? Collapsed brake hose (allows fluid in, but not out)? Bent slide pin?
 

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Discussion Starter · #9 ·
Update. I've been in Chicago on business these past two weeks. Finally got the brakes worked out. The piston seal was deteriorated, almost completely gone! Its was only the driver rear caliper. I think this car was in an accident in a previous life...

New caliper and brake fluid flush fixed the problem. Used some 60 grit sandpaper to deglaze the pads and rotor. Everything is working out great.

I used Valvoline DOT 3/4 brake fluid (this stuff is clear, old stuff was amber... was it worn or the amber ATE fluid?).

Word of caution for all XI and station wagon owners, these calipers are slightly deeper. I bought a rebuilt caliper from autozone and Pepboys. Both were NOT WIDE enough to fit pads around rotors. Ended up with NEW BMW caliper for list price!

Thanks for the help, the cellophane on the fluid resivoir and the line plugs i bought left almost no air in the line, other then the emply hose and caliper.
 
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