soft brake pedal / pedal drops / pedal pump
For so long I've been searching for my soft brake pedal problem, I think I finally knocked it. Posting this in case anyone else has the same issue. I searched so many posts and found a few with the exact same thing but no solutions. Now I cant find those posts, so making a new one.
Problem: slowly as I put miles on the car, I needed more and more brake force on the pedal to get enough stopping power. Driving the car every day I think I got used to it. But if I drove a different car I could really notice how much force I'd need on the G8 to get good braking. With enough force the brakes worked fine, it was just getting shocking how hard I'd need to press. Also if I was coming to a stop at a light or stopsign, I'd notice after I came to a stop the pedal would sink a little then get firm again. If I was slowly coming to a stop, and for some reason I'd get off the brake and back on quickly, I'd notice it was nice and hard after a "pump" where the pedal would slowly be sinking and if it went up a little it was hard like it should be. I've changed the pads and rotors many times while this problem was slowly getting worse and worse and no change, I've bled the brakes and even fully swapped out the fluid a twice and no change. Sounded like a classic master cyl problem. After searching here many times, I found a lot of posts with people with almost the same problem and quiet a few changed the master cyl and had no change. So I kind of let it go.
A few weeks ago I decided to check my front pads, even tho they were not that old I felt a very slight grind. One of the pads was worn much more at the top than the bottom, meaning one piston was doing a lot more work than the other. And I think I kinda remembered last time I changed pads a similar problem but not as bad. I assumed the pin was just drying a little and lubed the hell out of them.
Since my car almost had 90k miles, and I've had nightmares on old cars chasing caliper problems, I replaced the front calipers and threw in new lines. Problem gone, brakes feel nice and tight even with light pressure and no more fade after you come to a stop.
My theory: the pads were wearing uneven top to bottom causing the pad to get that slanted wear. But when you drive the whole pad would push back. Now you're on the brakes and only half the pad is touching the rotor, and the pedal slowly drops down with weak line pressure as the second piston is still moving on the uneven pad. Once the slanted pad is fully against the rotor with one piston out more than the other I get the line pressure goes up to what it should be.
Or I'm totally wrong. lol
If you have the problem I had, and your miles are getting high, you might want to check your calipers and make sure the pads are not bound up, the pistons not bound up, the pins dry and bound up. Anything that could be causing uneven pad wear top to bottom.