Hello All, I have a 2005 with a little over 300,000 miles that has recently begun pulsating when braking and sometimes does not stop properly. When slowing down, sometimes it doesn't slow down like it should unless I press firmly on the brakes. This is my 5th Prius and I know how they're supposed to drive, so I know something is wrong. I took it to the dealer a couple days ago and was told the reason for my issue is that the lower control arms were bad and one engine mount was worn and that that is causing the hesitation in the brakes. I went ahead and had the work done and then drove it home, but it is still having the same issue. I thought sure it was the actuator or something related to the braking system. I took it back to the dealer today. They adjusted the rear brakes and suggested I look at the rotors and calipers if I have any problems, but said the issue was fixed. It is not fixed. It is still doing the same thing and I can absolutely guarantee this is NOT a hardware issue. There are also no warning lights and I am not getting any codes other than a P0420, which I will deal with later. Dealer said it is not the actuator. Someone on the below Reddit thread () described something similar and said his local mechainc said it was the "swoop sensor" and after the shop replaced it, it was fixed. I have no idea what that is and have never heard of it, but I think he meant "speed sensor". That would make sense because that is what it feels like, but again, there are no lights or codes. I did a Google search to see if the speed sensor could be bad without lights and it said "that it is possible. I am stumped now because the dealer has no idea and doesn't notice, but I have driven these cars (including this one) enough to know how it is supposed to brake and now I cannot drive it because it is not safe. I had to really keep my distace on the SoCal freeway on the way home from the dealer today and had a couple close calls. Please help if you can. Thanks.
So with four or five cars under your belt yes you should know how they drive and you had no beep no tones no lights and the lights do work when you boot the car? I wonder if anybody has attempted to simply bleed the brakes have you ever seen the reservoir down or low I have a couple of mine I have four too and have replaced several actuators right here I have also bled the brakes on a couple that have come here and that fixed it hardware I've replaced every piece on a few cars and almost nothing on a few at 500,000 almost no noticeable difference in vehicles other than some vibration from the 500,000 and the cars with the new parts and I mean struts control arms lower ball joints brakes and links etc and you still have some noise just from near 500,000 mi I guess but nothing like you're describing here with your braking it almost sounds like there's air in the system maybe even the brake fluid won't match the pH that it needs to be at generally.
Update: In May of this year, I took it to a major hybrid repair shop in SoCal who also told me the same thing as the dealer. Eventually I was able to convince them that the actuator was the issue and they changed it with a used one with a one-year warranty. It worked fine for about 3 months, but the symptoms came back. The shop insists there is nothing wrong with it and that it's just me. That is BS, as I own several and have been driving them for years and know what it's supposed to feel like when braking. I don't think the shop wanted to do the warranty It work. It also has new brakes and drums. The Gen 2 loaner car felt fine to me and there was a noticeable difference. My car doesn't feel safe to me. Has anyone else experienced this and/or has any suggestions? I understand that there isn't always a code when these symptoms appear. TIA.
It sounds like air in your braking system and it was replace by a 'used' part with unknown miles and how long was it stored and under what conditions. Do you do a brake fluid flush every 3-5 years? If you don't, there's usually a lot of sediment at the bottom of your reservoir. That stuff gets sucked into your braking system and can reap all kinds of havoc in your electronic ABS system. The old manual systems are less temperamental and sludge doesn't seem to bother them that much. I flush out those old systems in trucks and SUVs the braking improves immensity; but those are much larger and heavier vehicles. I'd have someplace do a full brake fluid systems flush and see what happens. FWIW; brake pulsation is usually warped rotors.
Man let me tell you I put break actuators from cars that look like mad Max mobiles in my cars . Especially if it has the magic part number with the right suffix or prefix or whatever it is and usually getting for near free. I can do this job in about 2 hours flat I can also get air out without fancy tools if needed. Sounds like you may in fact have an air problem . I would personally bleed the back brakes first. See if ya get big shots of air do it until fluid streams out under pressure . Drive it . Still feels funny . Take out the blue ABS relays and bleed fronts manually like 30 yrs ago. Ride again ?
