A little back story: the last time that I did brakes on my own was for a 2000 Camry: I did the disc brakes in the front, and I did not do anything to mess with the brake fluid line. Yet somehow, after I was done, the brakes on the Camry felt spongy, but the car still stopped effectively. Now, the front disc brakes on my 2015 Prius need to be done, and because of this experience, I am on the fence about doing it myself. Can anybody give me advice on how to prevent sponginess when changing disc brakes so the same thing that happened on my old Camry doesn’t happen again on my Prius? Feel free to also suggest that Prius brakes should be professionally done and please explain your reasoning. Thank you and regards,
For starters, what work do you think the front disc brakes on your 2015 need? I am in favor of inspecting, and taking care of whatever needs taken care of, rather than treating "do the brakes" as some kind of a thing. You can do all of lift the calipers and remove the pads inspect the pad and rotor thickness and condition inspect the rubber boots on the pins and piston inspect the pins for smooth motion, regreasing if necessary inspect the condition of the "fitting kit" (spring clips where the pad ears slide), replacing if necessary without any opening of the hydraulic system, and none of that will change the feel of the brakes. But make sure you know about the car's brake self test and when it happens, and don't risk having it happen while you have the calipers away from the pads and rotors. If you replace pads and/or rotors, you will have to force the caliper pistons back. You can do that either without opening the hydraulic system at all (you'll be forcing old fluid backwards into the actuator under the hood), or by cracking the bleed valve so you force the old fluid out there, and making up the amount with new fluid you pour into the reservoir. I favor the second way, to avoid forcing possibly gunky fluid up into an expensive actuator. If you are careful (attach to the bleeder a tube already containing some brake fluid, routed upward, and open the bleeder only while pressing the piston), you avoid getting any air in, and you won't have changed the brake feel. If you have to rebuild the caliper itself, you will get air in of course, and have to bleed it out afterward.
You didn’t happen to open the bleeder valve to retract the old pads did you? (Not necessary, and poses risk of getting air in).
