hey guys. after changing my throttle body i still notice i am not getting the same gas mileage i was in the past. i noticed this since the day after my front brakes were done at the dealership. i know for a fact they didnt disconnect the 12 volt or the fuses because i watched them do the job through the window. i guess its possible they disconnected the fuses, but the tech sales guy i deal with said he never once did either one when doing brakes on a prius. i of course seriously questioned this since i have read here about how to do the job. the problem i am having is that is just seems sluggish, almost like the brakes are lightly engaging at all times. my mileage is at around 42.5 and its usually over 45. i do hear a noise that i never noticed before, but i could be hyper-sensitive since i just did that throttle body job. the noise is almost like a faint phone ring, and only happens at light acceleration, and not at all while coasting. today i noticed a pretty serious squeaking coming from under the car while i was at a drive through and using the brakes and not accelerating other than letting off the brakes. def sounds like brake squeal (not like low pad indicators, just like a regular squeal if that makes sense, not as high pitched), but i guess it could be something to do with the drive train. i understand this could have nothing to do with the brakes, but it does seem like quite a coincidence. i guess my question is, what are possible symptoms to not disconnecting the battery and fuses? the job was done very quickly, and i doubt that the tech bled the brakes, so im wondering if the pistons are stuck a little? thanks for reading.
just to add to this, i got new tires the same day as the brake job (tiger paw LRR 60k) and the 12v was replaced a month or so prior.
since "they" is me, thats entirely possible. my guess on that is no, though. but it could be a possibility the used tb i bought was also bad.
If your brakes are dragging, you will be able to feel (carefully!) if the rotors are warm/hot, following a drive. Check both sides. If you find any problems, most reputable shops offer 90 day warranty on work performed.
Ya, check the rotor temperature after a drive. Unless you were braking hard, they should only be warm and the same temp on each side. I wouldn't worry too much about the MPG drop if it was the only thing happening. New tires generally get worse mileage until they break in after a couple thousand miles. The possible brake noise is something you should look into. I still wouldn't expect to get your old mileage immediately after fixing the brakes.
Cool thanks guys. I figured I may just be extra paranoid since I did the tb myself. Every noise was probably already there. The tire break-in period is probably actually what's going on.
That's a good, easy test, but it matters how you do it. I wrote up a more thorough description here. The keys are, you have to: Get out of town (away from anyplace traffic/congestion will be making you brake) Once out of the congestion, cruise long enough (no touching the brake!) for everything to cool from when you were in town (I live near a place where a state route was rerouted, and now the old road is mostly deserted a lot of the time) Know a place on that road (say, a big, rarely-crowded parking lot with a wide turn-in) that you'll be able to turn into from the road, just slowing gradually using B-mode (no brake!) (and no annoying the traffic behind you...) and enough room on that lot that you can slow right to a stop. You can let B-mode slow you down to below 7 MPH or so, then select R and the reverse thrust will stop you in several feet. (If you try to select R at a higher speed, the computer calls you a dufus and shifts to N instead.) Feel free to clamp down on the brake at the exact moment your forward motion is zero and you're not moving backwards yet, shut the car off and park. The brake doesn't make any heat as long as it is only holding you still. It goes without saying, you have to scope out this whole route and be sure you can do it without creating any hazard. And if something unexpected happens in the middle and makes you brake, it's ok, you just have to go around again to make sure they again have a chance to cool. If I follow that protocol (when my brakes are working right!) I can feel the rotors right after stopping and they are all stone cold, just like any other cold metal underneath the car. That's the ideal test result. If a brake has been dragging, it may be very hot. Careful to avoid burns when you check. How important is it really to follow that crazy test method with no braking at all when you stop? I guarantee that if you have used the brakes even lightly to come to a stop at the end of the test, you will be amazed how warm the rotors get only from that, so it really masks the information you are trying to get. -Chap
Ok so I just did the test. Drove for 15 minutes on a deserted stretch (probably around 20 miles) and was able to never touch the brakes and get parked using your method. When I touched the rotors, they were both warm. Not necessarily hot, but definitely not cold. I wouldn't have wanted to put anything sensitive against them. They didn't burn my fingertips, but were definitely warm. If this means they are dragging, what is my next course of action. I'll obviously be taking it back to the dealer where the work was done, but I want to be informed and not let them fast talk me. Like I said, I know for a fact they didn't unhook the battery because I watched. But I can't be for certain this is why the brakes are dragging? Should I just go in and tell them that I suspect they are dragging? I don't think they'll even understand the way I tested them because I doubt they even know the car uses traction to slow the car down instead of the brakes. Please advise! Thanks.
