Excessive/Ghost Mileage after mechanic?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Johnsmith009, Mar 12, 2019.

  1. Johnsmith009

    Johnsmith009 Junior Member

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    Hi all,
    Advance TL;DR: I'm getting a lot higher instantaneous/some lingering (At higher speeds, decelerating for a second then going back to the same acceleration halves or entirely removes it) L/100km ever since a mechanic visit.

    So initially, I had to just go and replace my rear brake pads, as they were wearing quite thin since apparently they had seized. Strapped for cash, I just asked the Toyota mechanic how long I can ride it out, and he said "As soon as it starts squeaking with the brakes, you need to come in". I tried really hard to use exclusively regenerative braking for the next 3 weeks, no squeaking. Then when I finally have enough *and* get an appointment before the weekend, I'm 2.5 cities away. So to make it in time, I'm accelerating quite a bit, primarily in power mode, and I don't recall any hard brakes, just hard acceleration. Definitely did end up using friction brakes a bit, but no squeaking. As I come into the shop, it smells horrible. I thought it might be the engine, but he said it was the brakes. Apparently they were also quite hot.

    Supposedly, extremely hot, as he tells me there's now a brake fluid leak, and he'll have to replace the caliper, as its a safety hazard to drive (and quite frankly I don't want to drive with that kind of damage anyway).

    I left it overnight to get this replaced, to my wallets dismay. Its important to note they only changed the brakes. All maintenance and recalls were done in a visit in January.

    Immediately I noticed a drastically lower fuel efficiency, ranging above 10L/100km after just barely crossing and maintaining the "ICE threshold". (Example below, not sure what its called). It stays that way until my acceleration stops increasing and just needs to maintain speed, to which it levels out around the typical 5L/100km.
    upload_2019-3-12_21-29-0.png
    "Okay, maybe its cold from overnight, or its just got some breaking in to do. Not in a position to drive it more than 8k, so I'll try monday."

    Monday I go on a 350km trip. Sunny skies, +4C. No change whatsoever throughout the entire trip.

    The key details I've noticed are:
    • Acceleration itself seems to be fine. It goes a bit higher on the HSI meter than what it should at times, but the actual speed itself seems to be fine. I'm hesitant to say its even gotten smoother. Probably placebo.
    • BARELY passing the ICE threshold from a complete stop kicks the instantaneous efficiency to, according to the hybrid assistant app, >16L/100km usually. This used to be 5-6L at the END of the ICE threshold (before the PWR threshold)
    • Just before the acceleration starts dropping (I reach my top speed at that level of pedal depression and begin to coast) it begins to drop down to the 5-7L mark, however slightly higher than I remember it typically being.
    • Almost at any point above 30km/h, I see "ghost" usage. In this I mean, the usage stays at around 5-7L/100km even if I go below ICE threshold. Below halfway away from the ICE threshold, theres no impact in L/100km. However, completely letting go of the accelerator for about 1 second (allowing the L/100KM drop to 0, times vary) and pushing it the exact same amount (or more, just below ICE threshold) will keep it at 0L/100KM, with no noticeable difference in sound, performance or speed. This is what upsets me the most.
    • On rare occasions, smooth regenerative braking to-complete-stop will increase the L/100km briefly up to around 10-11L/100KM, until I am fully stopped. It's not a display glitch because I can hear the engine turn on, then turn off. This doesn't seem to be replicatable on demand, and never happened before.
    I've uploaded the Hybrid Assistant report for an 11km circuit around a city so you can judge my driving habits. Hopefully there's something insightful in there.
    cstuff(dot)win/hybridreport.html

    (Why can't I post links? I've made more than 4 posts. I'm reminded of eric andre near the DNC.)


    Side question, I've noticed it marks "Pulse" as "full capability of ICE" and "Glide" as "No mechanical or electronic motors". Is this correct?
    I've been pulse-and-gliding as just below the PWR threshold, then gliding just below the ICE threshold. Surely a frequently recurring full-PWR isn't good for the engine's longevity? And its a hybrid, shouldn't it glide with electric?

    Thanks!
     
  2. bisco

    bisco cookie crumbler

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    pulse just above the eco line, glide just above region line. but i suspect he messed up your brakes, or drained the 12v.
    report your post and ask about the link problem
     
  3. Johnsmith009

    Johnsmith009 Junior Member

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    Above region line? Do you mean Regen/charge line?
    Will do, thanks.
     
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  4. bisco

    bisco cookie crumbler

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    Yes, look at you tube for various video instruction
     
  5. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    Do you understand that? If so you're a better man than me, lol. Anyway:

    Front or rear brakes, do you know? Also, how many miles on this car?

    Right away I'm thinking dragging rear brakes. Who's doing your brakes, an experienced Toyota mechanic? Or?

    The 3rd gen Prius has rear disk brakes, with a tricky, integrated parking brake mechanism. Short version of the story:

    There's a stubby pin on the back of the brake pads, that must be positioned between the spokes on the brake caliper piston face, and be well-seated in the gap, locked. If the piston manages to rotate so that the pin rides up onto a spoke (or was thus from the get-go), you will have terrifically off-balance brake pad contact, and constant brake drag.

    When the rear brakes are reassembled you need to:

    1. Ensure the pin and caliper piston are oriented correctly.
    2. Ensure they stay that way, are well seated.

    The method:

    1. Reassemble correctly.
    2. Press brake pedal multiple times. (do not use parking brake)
    3. Reconnect 12 battery negative cable.
    4. Go for short test drive, and go real easy on the brakes.
    5. Getting back, press/release parking brake several times.
    6. Chock front wheels, raise rear of car, and try spinning the wheels. They should fairly easily spin a rotation or two. Slight drag is normal.

    A quick check for current status:

    Feel the rear brakes after a drive; they should be slightly warm at most.

    Brake condition if they're screwed up:

    1. Inside pad in particular will have bevelled wear.
    2. Brake disk will maybe have scoring.
    3. Inside face of disk will be about 50% rusty, due to lack of contact.

    Brake info attached. Excerpt, showing the correct rear brake piston orientation:

    upload_2019-3-13_10-12-43.png
     

    Attached Files:

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  6. bisco

    bisco cookie crumbler

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    Not really...
     
  7. Johnsmith009

    Johnsmith009 Junior Member

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    I assume you were talking to bisco. I guess I worded it poorly? Check the bullet point list at the end for more in depth explanation.

    Back brakes were the ones in poor condition, but he didn't mention which brakes were hot nor did I check myself. 193000km.

    The Toyota dealership for the city, genuine/official Toyota mechanics. They have a few mechanics that look younger than me though...

    Now it's my turn to not understand. I'll go in to ask and tell them this information, but comprehension is beyond me.

    One thing: Brake drag makes sense for worse fuel efficiency accelerating vs maintaining speed, but I don't think it would have the effect of lingering usage in the eco threshold (where it tends to be electric only) and I certainly don't think it has anything to do with fuel usage spiking while braking. Best humble guess I have is a combination of discharged 12v/poorly assembled brakes.

    I'll go to the mechanic today and see what he has to say.
     
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  8. bisco

    bisco cookie crumbler

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    I think ‘lingering usage in the eco threshold ‘ is a difficult phrase.

    And I wouldn’t put much stock in current mpg’s, but track long term averages manually calculated at the pump
     
  9. Johnsmith009

    Johnsmith009 Junior Member

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    Step one:
    Go above the area marked with red in the image

    Step two:
    Go below the area marked with red in the image

    Step three:
    Observe engine continuing to use 5-6L/100km for no apparent reason

    Step four:
    Release the gas pedal all the way, and immediately push it down to the same position

    Step five:
    Observe it going the same speed, same position in the area indicated, but taking 0L/100km instead

    Sorry, I tend to overcomplicate my language, hard to get arbitrary concepts across without knowing the proper terms. tapatalk_1552662809561.jpeg
     
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  10. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    I'll sometimes see engine-off propulsion, with the HSI bar slightly to the right of the median mark, IF the hybrid battery charge display is all the way up to the top. Typical scenario would be after coming down a really long hill.

    Still, the low-hanging fruit for you, is to just feel the wheels after a drive, see if any feel unusually hot, hotter than the others. I'm still betting they've misassembled the rear brakes; it is so easy to do.

    Step two if you can manage it: raise the rear and try spinning the rear wheels, with the parking brake off. If you don't have access to a garage and a floor jack, in a pinch, you can do it one side at a time, with just the scissor jack that comes with the car.
     
  11. bisco

    bisco cookie crumbler

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    1) engine on

    2 and 3) engine often remains on

    4) engine shuts off

    5) this is normal, and part of the ‘pulse and glide’ protocol to increase mpg’s through hypermiling
     
  12. Johnsmith009

    Johnsmith009 Junior Member

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    But what I'm saying is, shouldn't 3 be identical to 5? 5 is not the problem, 3 is.
    I feel like 3 didn't used to happen.
     
  13. bisco

    bisco cookie crumbler

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    Should be? Not in my experience, although it does sometimes happen.
    The issue, as I understand it is that the engine is controlled by software, of which throttle input is one small factor.
    Drive by wire allows for many variables, mostly directed to pollution control
     
  14. Johnsmith009

    Johnsmith009 Junior Member

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    At this point I'll likely only have time to directly drive to the mechanic, but in the event I cannot make it, I'll do these and report back.
    No clue how to use the scissor jack. Guess I'll learn.
     
  15. Johnsmith009

    Johnsmith009 Junior Member

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    Very odd. With a full battery, no excessive acceleration and an engine on time of >5s, I would think the smart decision would be to engine off and let electric take over.

    I guess if that's intended behaviour I'll leave it be, though.
     
  16. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    It's under the hatch floor. Yeah when you've got some time, get the Owner's Manual out and have a look. It's good to get familiar with it, practice, before you're really needing to use it, with a flat.

    Owner's Manual says to chock the tire diagonally opposite to the corner you're raising, which is good advice, except: there's no supplied wheel chocks, and I think 99% of owners don't heed this advice. Without chocks, just set the parking brake, good and solid, and do this on level ground, preferably concrete.

    Besides wheel chocks, another good item to have is a small square of plywood, say 3/4" thick by maybe 8" square, to act as a sub-base under the scissor jack, if using it on earth, or even asphalt (especially in summer).
     
  17. bisco

    bisco cookie crumbler

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    Agree, seems counterintuitive, and on newer generations, I think they have refined it for higher epa mpg ratings
     
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  18. Johnsmith009

    Johnsmith009 Junior Member

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    When you say with the parking brake off, you mean the footbrake pedal on the left, correct? Not shifting it into neutral? That seems dangerous if neutral.

    Side note, spin the wheel and do what exactly? I have no frame of reference for how difficult they should be to spin.

    Also, feel what part of the wheel? There's only so much I have access to.

    Update on the mechanic: my mechanic assured me that the person working on the brakes was a certified hybrid specialist at the Toyota dealer so I don't know if he could have missed some of the brakes but I'm going to get them checked anyway on Monday.
     
    #18 Johnsmith009, Mar 15, 2019 at 5:07 PM
    Last edited: Mar 15, 2019 at 5:34 PM
  19. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    Yes parking brake, aka foot brake, aka emergency brake, off. You don't want the rear wheels locked. No need to be in Neutral.

    With a goodly push they should continue to freely rotate one or two revolutions.

    If on the other hand, if it's hard to even turn, stops immediately, you would know they screwed up.

    The outside face of the rim, near the centre. You're basically trying see if a wheel is dragging; if it is it'll be hot, at least significantly hotter than if you feel the front wheels.
     
  20. Johnsmith009

    Johnsmith009 Junior Member

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    So just by contact alone the front wheels should be warm? I went and touched what I believe to be the *calipers* and they were cold.
    On the plus side, the brief period I had the wheel up, I think it was pretty sturdy. I didn't push it as hard as I could have (given its a tire, they're heavy on their own) but it went under 1/4 around. Reinvestigate Monday.
    Thanks!
     
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