Changed caliper, pedal is only firm after I pump it

[repenttokyo]

So I had new pads and rotors installed Friday. Over the course of the weekend, the bracket holding the left front caliper came loose because of a stripped bolt. I replaced the caliper, and now My brakes still stop the car, but I only get really firm bite if I pump it once or twice before applying constant pressure. What could be causing this? Air in the lines? The fluid level seems to be good - I added a bit just now because it seemed low, and it seemed to improve things, but I might be imagining that.

[ArtemLepilov]

Did you bleed them? If not - bleed them, if you have - bleed them again until its always firm.

[DanDombrowski]

Bleeding the brake system when you're flushing the fluid is a walk in the park.

Bleeding the brake system after opening up a line or rebuilding a caliper can be a nightmare. The only real instruction is "bleed, then bleed again, then bleed again, then when you're absolutely sick of it, put the car back together. Drive for a few days, then bleed again".

When I rebuilt the calipers on my volvo, I had wasted so much brake fluid that I started recycling it (still new fluid) as I bled the calipers (so sue me). When I was finally sure I had all of the air out of the lines, then I did a bleed with fresh fluid.

Anyway, the inside of the caliper is cast (not machined) and can trap tiny bubbles from being released when bleeding. One trick I've learned is to tap the caliper with a hammer to get some of the bubbles to let go and get flushed out.

[DanDombrowski]

Oh, one other thing I've thought of. If you have ANY play in the brake system, you will get a soft pedal until you pump it. When you were talking about how you were getting a clacking noise with the brakes and the stripped bolt on the caliper carrier, you may have a few brake alignment problems which would DEFINITELY lead to a soft pedal.