MY350Z.COM - Nissan 350Z and 370Z Forum Discussion - rear brake piston doesn't disengage

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rear brake piston doesn't disengage

I noticed my 05 350z driver side rear brake is not releasing so it causes the brake extremely hot after 10 min drive. So far I've not felt any drag. I took the tire off today and found the piston isn't releasing. It bites the pads so tight that I can't even take the caliper off.
so, my question is, in normal cases, how does the piston go back in when my foot is taking off from the brake pedal? I somehow feel the pad always touch the rotor even when I'm not braking, is that right?
right now, the piston is tight and I can't push it back in, what can I do to fix it?

thanks!

Your rotors and pads are likely trashed from the heat you generated to lock up the caliper pistons anyway, so see if you can jam a prying tool in there to retract the piston. If that doesn't work, then cover the part where the rotor and pads meet in penetrating oil, wait an hour and see of you can't slide out the assembly with a hammer and a drift.

If you don't feel comfortable using brute force on your brakes, then take it to a shop, where they love using brute force.

What part of WA are you in?

Thanks for the info. I can take the caliper off. The problem is the piston doesn’t go back.

I tried to release some pressure by opening the bleeder to let go some fluid. This can help push the piston back so I can take it off to examine. But once i push the brake paddle, it will get stuck again. So from my experiments I think the pipe is ok because the brake still works and the fluid can go in. But I don’t understand why it cannot go out. The piston can be pushed back after release fluid from the bleeder so I guess it wasn’t get stuck in the caliper as well.

Probably rusted; replace the caliper. Just had to deal with this on my daily driver recently. I could compress the piston, but it would lock up once I used the brakes.

If the piston retracts when you bleed it but won't retract when the system is closed, then you might have a problem up the line. It might be your ABS actuator or a bad proportioning/metering valve (I don't know for sure on this application, since the brakes on my Z have been pretty solid since new and I haven't needed to get into the system beyond installing stainless steel brake lines at the caliper.) Check the FSM for troubleshooting.

If it were me, just to be sure, I'd pop the piston out of the caliper and inspect it to see it can or should be rebuilt. I use compressed air and some wood wrapped in a towel to catch it when the piston shoots out, but if you don't mind the mess, you can just push it out with brake fluid (make sure someone keeps topping off the reservoir). If it's bad or won't come out, then yes, a new caliper should be on your wish list.

I'm always going to recommend you test a part before you replace it, but if you don't want to take it to a shop, then do what you can afford to do.