Overextended rear brake piston, help

[BucDan]

Was replacing my rear brakes. Used OBDEleven to retract the EPB piston, it retracted, only a little bit. I was able to wiggle the caliper off. Now comes time to reinstall the caliper, it wouldn't fit, tried to hand press it, tried to open it again in the app, no go.

Went ahead and tried to Maybe close and reopen it, because maybe it got stuck, no luck, it wouldnt retract. Now, I tried it again, now the piston over extended. I feel like an idiot.

Can't retract it back anymore in the app Any way for me to come back from this?

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[Jk79]

The option to release parking brake doesn’t actually retract the caliper piston. Normally once you’ve released the electronic brake and unbolted the caliper, popped out the old pads, you do have to press in the piston with a clamp in order to fit the caliper and new pads back over the rotor. Once you get it bolted back on and re engage the electronic parking brake you would simply press the pedal a few times to prime the brake, forcing the fluid and piston back into place.

Re engaging it however does apply pressure on the piston. If it’s not already on the rotor it can overextend.

If the piston is over extended and you can’t even get a clamp in there to push the piston in, you’d likely have to disconnect the brake line from the caliper. should move pretty easily at that point.

[BucDan]

The option to release parking brake doesn’t actually retract the caliper piston. Normally once you’ve released the electronic brake and unbolted the caliper, popped out the old pads, you do have to press in the piston with a clamp in order to fit the caliper and new pads back over the rotor. Once you get it bolted back on and re engage the electronic parking brake you would simply press the pedal a few times to prime the brake, forcing the fluid and piston back into place.

Re engaging it however does apply pressure on the piston. If it’s not already on the rotor it can overextend.

If the piston is over extended and you can’t even get a clamp in there to push the piston in, you’d likely have to disconnect the brake line from the caliper. should move pretty easily at that point.

Ok, I feel like an idiot. I didn't use a clamp on it after I released the EPB, I just assumed it fully retracted and that was it.

I called Audi San Diego here, they wanted $1000 for the part and installation. Screw that.

I ended up having to pull the cylinder out with the boot attached to it and hand twist the piston back into place on the threads, but having troubles getting the boot back into the caliper. Been a messy job so far for a first time rear brake and rotor change that was suppose to be easy.

Trying to do my on basic work on this car and I've been messing up lol. What a failure.

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[BucDan]

After reassembling the caliper and piston, will I have to clear out any codes before the car's computer will let me manipulate the piston?

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[Robdukes]

Best bet. Get one of these. Helped me on my B5 in the past and now will help in the B8. Just a handy tool to have around. SmartSelect_20190427-182943_Amazon Shopping.jpg

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[jimrobbington]

You can "rent" caliper/piston tool from like AutoZone for free, they just charge a deposit. This will allow you to press in pretty much any size caliper piston easily.

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[BucDan]

Any possibility that when I get the Caliper reassembled, the electronic motor doesn't work due to a fault code?

I have a feeling it won't be so easy, knowing my luck.

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[kielp]

Any possibility that when I get the Caliper reassembled, the electronic motor doesn't work due to a fault code?

I have a feeling it won't be so easy, knowing my luck.

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Don't worry about codes. The EPB module isn't that smart. Open the reservoir and crank the piston retractor to get it back - the electronic motor won't know/care. As long as you didn't tear the boot you're fine. An Autozone rental piston tool works well. I own a Harbor Freight tool that works well.

[BucDan]

Got it back together. Just have to bleed it to get all of the air out. Thanks guys.