My civic eg was sitting over the winter with the motor out and I took it out this week to drop my new build-up. And also installed new gsr rotos w/ new brakes. I bleed the brakes and it will not get hard. It will stay hard for about 30 sec. and it will be soft again after that. I change my master cylinder too. Can it be my brake booster? Everything was working fine when it was stored away. Is there anything else I can check?