Hello all, just purchased a 2007 Prius touring with ~145k miles. No warning lights or issues reported from seller or concerns from CarFax. Drove it 2 hours home with no issues. A couple days later, while driving, the TPMS light flashed indicating a problem with the sensors. I imagine one or more have died as they’re likely the originals. Not too worried about that. However, I noticed yesterday that after driving for a few minutes, commute is usually above 40-60 mph, when I stop at a red light, there is a slight, intermittent pulsating/throbbing in the brake pedal. It doesn’t happen every time, but often enough that I am concerned about it. No other warning lights have come on (no CEL, Red triangle, brake, etc). Would this be the brake actuator or ABS system? If so, am I essentially looking down the barrel of a $1000+ repair? Is it still safe to drive if this is an issue? Please let me know what you all think. Thank you!
In any case, did you check your tire pressures? You can't just assume the sensor is faulty. You have likely found the reason the car was for sale. Yes, a new Brake Pump/Actuator/Accumulator (all one unit) is in your future. The correct advice is that no brake problem is safe to drive with. If you have no brake dash lights illuminated, you can continue to drive and you might find it doesn't get worse. I'd have a plan in place for what I'd do when brake warning lights light up the dash.
Yes, double checked that after the light came on. It’s cold here so they were a bit lower than the recommended PSI but not by more than 1-2. Also, when the light comes on it flashes for a while before turning solid. I believe this is indicative of a system fault, but could be wrong. My apologies, didn’t see the second part of your reply. That is unfortunate news, hopefully those lights don’t come on too soon. Thank you for the insight!
I disagree, diagnosing the problem requires more driving/monitoring and there's multiple systems in this braking system to ensure they work and its almost impossible for all the systems to fail at the same time. Now if you take it to shop with this concern, because it's brakes-based, odds are before they even start a diagnosis they're going to sell you all new brakes and rotors to "solve" it, then they'll come up with more repairs if it doesn't. So diagnosing the problems first will likely save you lots of money. Can you further explain the "slight, intermittent pulsating/throbbing in the brake pedal" ? Are you decelerating when it happens? OR just sitting at the red light? At what speed does it occur? Does it happen more or less if you're turning to the left or right while it occurs? Can you learn to re-create the sensation? Are there any other strange noises? What happens when you do super hard emergency braking at speed in an empty parking lot?
It only happens when completely stopped at a red light. When moving, there are no braking problems at all. They feel completely normal outside of that few seconds when stopped. I did a few hard brakes and had no problems at all. as for explaining the feeling, it’s almost like the vehicle is trying to scoot forward or like the entire car gets a slight shake. I feel it mostly in the brake pedal, but rode with a passenger for the first time today and they also felt it. It’s sort of like a small jolt, but not at any regular rhythm.
Seem most likely that if you feel something in the brake pedal when braking while moving it would be a concern. But if you're feeling something in the brake pedal when the vehicle is not moving and your passenger is feeling something too it's probably not brake related. You could try pumping up the brakes next time you have that experience and see if that changes it. If you're noticing any changes in the pedal beyond it getting harder to press, you might want to bleed the brake lines and see if that addresses the symptoms?
Okay, I believe you may be right as there are no issues when actively braking. Only when completely stopped does the incident occur. It may be something with the engine, but I am not sure. I saw a very old post explaining something similar, and they described it as diesling, or the engine burning off whatever residual gas is left at the top of the engine. I am not sure if that is right, but it’s the only similar thing I found.
If you can recreate the symptom while someone else is driving then you could jump out and pop the hood as well as walk around the car to search for the source of the vibration.
if you read my whole reply rather than taking one statement out of context, you will see I said basically the same thing you said, but in two short sentences rather than three paragraphs. But no matter. So, it sounds like it is more a thing outside the brake system causing the car to lurch against the brakes, and that is what you're feeling. The lurching is a thing, and you should be able to find more on that with a search of old posts.
It could be a low rpm gas motor roughness. Look at the charging picture on the display, does it show the gas engine running or off?
Sometimes when our 2007 comes to a stop the MFD will show the ICE off, actually no current moving in any direction, yet the car still vibrates as if the ICE was on and idling. (Nothing but the fan running in the climate control, temperature set below ambient temperature.) Usually it turns off after a while. I don't particularly feel this at the brake pedal though. The MFD display otherwise seems to show the state of the car correctly, albeit with a few seconds delay sometimes. That is, when we come to a stop and the car makes its little death shudder (very slight lurch when the ICE turns off) I can count to one or two before the display shows that. When that pedal pulsing at stop occurs the OP should try putting the car in Park. Even if the ICE is still on, but not shown as such, that would effectively disconnect it from the wheels so that it cannot make the car shake, so that the pulsing on the brake from that cause would go away. My guess is that it will still be pulsing because it is an ABS issue and not an ICE issue.
The situation you explained in the first paragraph may be what I am experiencing. I have looked at the energy monitor screen to see where the pulsating is coming from, but there is no movement or action on the screen at all during these times. I suppose it may just be the ICE engine kicking on? I will try your tip next time about putting it in park to see if the issue continues. Can you elaborate on why you think it may be an ABS issue?
