2003 Mini Cooper Rear Caliper Piston Stuck

MINI COOPER S
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SIDPATEL
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I have 2003 Mini Cooper s, I have replaced front rotors and pads. Now I am trying to replace rear rotors and pad. I tries pushing caliper piston in using special tool prescribed. But it would not go in. I already broke one tool. I noticed parking brake is also using same piston to apply brake. Can some one help if there is any electronic control which stops piston from going in?
Thanks.
Mar 7, 2007 at 12:36 PM
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STRAILER
  • ✓Experienced Mechanic
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Try removing the ebrake lever off the caliper, and then reset the piston.
Mar 23, 2007 at 4:33 AM
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AJROSSI
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The disc on the caliper has four small holes in it. You need a tool that will fit into the hole. You take a rachet and have to turn the caliper disc like you are screwing it in. Apply pressure while you are cranking it in to get it far enough back to put in the new pads. Using a regular caliper compressor will not work with calipers that have an emergency brake attached. You can crank it as hard as you want and it will not budge, needs to screw in. I just went through this over the weekend. The tool I purchased at autozone was $8 but was the wrong fit so see if you can purchase one at a Mini dealership. Use an 8mm Allen to remove the caliper pins and be sure to clean and regrease the caliper pins.
Jul 1, 2008 at 5:48 AM
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AJROSSI
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expensive version of the tool for retracting the caliper.

Autozones is about $9, could not find it on there website but they have it here

it slips onto the end of a rachet. It is a square with different sized pins on each of the six sides. None fit perfectly, one side has 4 pins that don't line up, but if you off center it and use 2 pins of the 4 you can crank it in. My suggestion is to use a grinding wheel on the side of the square that has two pins only that are too large to fit in the caliper. Grind them down a bit and they should line up and fit in perfectly. You need to push it in hard when cranking it to get the caliper to compress.
Jul 1, 2008 at 6:20 AM

Suggested Repair

Remove the parking-brake lever from the rear caliper, then retract the piston by turning it clockwise with a pin tool that fits the holes in the piston face while applying inward pressure. A standard compressor will not work because the parking brake uses the same piston. Remove the caliper pins with an 8mm Allen wrench, clean them, and regrease them before reassembly.

Conversation Summary

The owner of a 2003 Mini Cooper S had replaced the front brakes and could not push the rear caliper pistons in with a standard tool, breaking one tool. They noted the parking brake acts through the same piston and asked whether electronics were blocking retraction. Advice was to remove the parking-brake lever and screw the piston in with a fitting pin tool while pressing, rather than compressing it, and to clean and regrease the caliper pins.

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