Hello Everyone, I have a 2009 Prius base model, and I've been having two different brake problems. I am hoping someone could shed some light on it before I go to a mechanic: 1) The brakes let loose and retighten(reclench) when I hit a bump or pothole when braking. 2) The brakes clench up real tight even though I apply the brakes gently when city driving and conditions are wet. Any thoughts are appreciated. Thanks
welcome to priuschat! these are common issues, nothing to worry about. is it a recent purchase? you might want to take it to a dealer to see if there are any recalls. all the best!
Thank you very much. I have had the car for a year now, and have brought it to the dealer in the past to address the one open recall (water pump inverter). So does this mean that the car is supposed to behave like that? The clenching up in city driving is pretty annoying, and I'd like to figure out a solution if possible.
I can't really speak to #2 w/o driving your car but as for #1, it might be normal. See Poll: Are Prius brakes a problem? | PriusChat, for example, esp. if you see the yellow skid light blink while that happens.
the brake rotors rust very easily because the regen does most of the braking. a regular habit of throwing the car in neutral and braking will force the pads to scrub the rotors and may help reduce the grabbing.
When the brakes are wet, they do tend to grab a little bit. What happens is the rotors get rusty. Once they are rusty the brakes get grabby. After a few stops the rotors are cleaned up and the brakes work smoother. To clean them quickly drive the car no faster than 40 MPH MAX, shift to N and then brake to a complete stop. You may notice a difference in the amount of stopping power. Only do this if you are in a area where no traffic is around. Two or three stops should do the trick. Rotors do tend to rust overnight in high humidity areas and or if it rains. Concerning the brakes feeling funny when you hit a bump. Completely normal. Watch the dash when the brakes are doing it's thing when you hit the bumps. You will probably also see a yellow light flashing. Usually the skid control light will blink. As previously said, it is normal. FWIW, the Gen III seems to have a little better system than the Gen II IMO. At least when I am braking and hit a bump, I don't feel the pulsing of the system like I did with the Gen II. It is suggested that when you hit a bump continue to hold firm pressure on the brake pedal and simply ride it out. Once the road smooth's out, the braking action should return to normal until the next time you brake and hit a bump at the same time. I think the OP is fine. However if the car suddenly changed overnight then I would have it checked out. The things the OP described IMO sounds perfectly normal for a Gen II Prius. Ron (dorunron)
Just to add to what Ron and others have said about this, I found that this effect can be more or less pronounced depending on what tires you have fitted and the pressure you are running. Sadly, some brands that claim higher LRR, can be more pronounced. Having said this, I feel that it is more of an annoyance than a danger. Make sure you run the correct pressure so that you are getting even tire wear across the entire width. I have found running pressures at the placarded levels (35F/33R) to give a wear pattern (excessive wear in the shoulders) indicating under-inflation. Therefore I run my tires at 39F/37R. YMMV, so you be the judge of how your tires are wearing. hope this helps.
Might be related to your #2: Very infrequently, when just starting up and moving in reverse, I'll find there is no modulation when braking: they're either off or locked. The first time I experience this I was backing up to get out a parallel parking space. I touched the brakes and the car came to a sudden/complete stop. I was momentarily convinced I'd hit the car behind; it was that abrupt. This behavior usually persists until I start rolling forward, in Drive. I'm pretty much convinced it's not rusty rotors or whatever, seems more like something in the electronics, brake programming, both due to the extreme behavior, and the way it's so very infrequent, and there, then gone. Again, our's is a 3rd gen, with rear disc brakes, so just fwiw.
