Brake fluid / warning lights

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by rifis, Dec 15, 2018.

  1. rifis

    rifis Junior Member

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    When I started my 2010 Gen 3 (just short of 40K miles) tonight, the red brake light, yellow ABS and yellow brake system warning lights, and yellow swerve indicator all came on and remained on as I drove.I confirmed parking brake was disengaged. Braking at slow speed felt normal; no drag perceived as car rolled forward with foot off brake.

    Once home, I looked at owner's manual, and then checked brake fluid reservoir - dry, as best as I can tell w/small flashlight , now, at night.

    What is likelihood that empty reservoir explains all warning/indicator lights?

    Car had oil change at Toyota dealer less than 4 months and 1000 miles ago. All fluids were reported "normal". I don't think I have checked brake fluid level in very long time.

    IF their report was accurate, then sounds like a leak has since arisen. Is simply replacing fluid and watching most cost effective way to evaluate and confirm leak? Can some other abnormality cause relatively rapid loss of brake fluid? Car spends the very vast majority of its life in my garage. I don't see fluid on the floor - would I expect to if a slow leak was present? If leak is present, where is likely location, and what is likely cause?
     
  2. bisco

    bisco cookie crumbler

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    wow, i don't think i have ever heard this before. did your brakes work okay?

    just because the dealer reported normal, doesn't mean they actually checked.

    it might be an extremely slow leak, with no fluid or staining on your garage floor.

    top it up and keep an eye on it.
     
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  3. ChapmanF

    ChapmanF Senior Member

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    Empty reservoir could explain warning lights, but nothing explains empty reservoir.

    If it really was empty, there is now air inside the head end of the brake system, which will need to be bled using the longer procedure within Techstream.
     
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  4. rifis

    rifis Junior Member

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    Thank you, bisco and ChapmanF.

    I haven't been here in a long time. You are 2 of the members I was hoping would respond.

    The oil change was "free"; part of the original purchase price. They might have had additional reason to check ; they might have had reason to not check. They did try to convince me to have them replace air and cabin filters the same visit; they were mildly displeased when I declined. I'm miffed I didn't check brake fluid myself.

    Braking does feel normal. Will have better idea if reservoir is totally empty tomorrow.

    IF air is inside head end, would I know it while braking?
     
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  5. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Here's hoping it's just hard to see the level. Get a good light on it, could be just very clear. Either way, those lights are trying to tell you something.

    Where in the world are you btw.
     
  6. qdllc

    qdllc Senior Member

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    Check every wheel (take tire off). If there’s a break in the line, this will be the most likely place it will be. Otherwise you end up inspecting every inch of the line back to the master cylinder.

    On another vehicle I had a minor leak on the inside of the car. The seal on the mechanism going through the firewall to the master cylinder had worn out.
     
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  7. bisco

    bisco cookie crumbler

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    i would think the brake pedal would feel suspicious if there were air in the lines, but i'n not familiar with the differences between prius and regular hydraulic brakes where you get the spongey effect.
     
  8. Raytheeagle

    Raytheeagle Senior Member

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    I had a situation in a previous car after repairs to the rear from someone hitting me that the brake line was against something and caused it to rub through. This led to the brake fluid leaking out and the pedal dropping to the floor when I pushed on it:cool:.

    Ended up having to replace the master cylinder due to air in the system, but if the reservoir is empty, I’d look for fluid somewhere. Worth confirming ;).

    Good luck and keep us posted (y).
     
  9. sam spade 2

    sam spade 2 Senior Member

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    Let's assume for a minute that it wasn't "dry", just quite low.

    As brake pads wear down, the fluid level in the reservoir goes down too.
    IF......the level had not been checked for maybe 5 years......it easily could be quite low without there being any leaks.

    And yes, low fluid could be the cause of the lights.

    If it was bone dry, then it's time for complete brake service: New fluid, bleeding and pad inspection.
    Just don't let them sell you rotors that you don't really need.......which happens quite often.
     
  10. sam spade 2

    sam spade 2 Senior Member

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    Air in the system will NOT damage the master cylinder.
    If it was bad, that was NOT the reason.
    It is possible that it wasn't bad at all.
     
  11. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I'm putting all my chips on "the fluid was so clear I didn't see it". It'd be a good outcome. Still, those lights...
     
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  12. rifis

    rifis Junior Member

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    Today I got a good look down into the reservoir from above with a good light. Bone dry. I secured 2 quarts of approved brake fluid and then started filling. Immediately I saw the level rise when viewing from the side. Before half of first quart was in, level was just above "max", and remained there.

    Started up car in garage. Same warning /indicator lights appeared. I backed car out of garage; first time I touched brakes w/car in motion, warning/indicator lights disappeared. No fluid seen on floor. Pulled car back in. Brake fluid level now a bit below "max" line. I drove, using this car, back to auto supply store to return 2nd quart. Upon return to garage at home, fluid level now lower still to about 1/2 way between max and min.

    I will be having my local (non-dealer) repair shop look for leak tomorrow. They replaced rear caliper and rear pads 10 months ago.

    Any thoughts?
     
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  13. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    If you enter the car through the passenger side (after the car's sat, say overnight), pop the hood, and check brake fluid level, it'll be relatively high. If you then open driver's door, pumps activate, and the brake fluid level drops maybe 1/2". You can actually watch it happen.


    Get them to check (and maybe demonstrate to you) how freely the rear wheels are spinning when the car is raised. They should easily free-spin at least a revolution, or two, with a good push. If the wheels drag badly, they've screwed it up, it's (too) easy to do:

    It is critical when assembling the rear brakes that the caliper piston be in an "X" orientation, so that the stubby pin on the brake pad backing plate falls between the spokes on the raised cross pattern on piston face. Also, the brakes need to be well seated thus, with multiple brake pedal pushes, and perhaps a test drive, before applying the parking brake (which will attempt to rotate the piston, the pin is there to stop it).

    If the pin ends up riding up on one of the spokes on the piston face, you'll have constant drag, bevelled pad wear, a zone on the inside face of rotor that's rusty (from lack of contact), and scoring on the rotor's outside face.

    See attached for more info. Also attached brake bleed instruction, requires car to be in Invalid Mode:
     
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  14. Robert Holt

    Robert Holt Senior Member

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    Are you in a high salt or high rust zone? I have had brake lines corrode through, and the first sign of those initially very tiny holes was a slow seeping type of leak. Please check uunder the car for corrosion on the brake lines, as that slow leak, if due to corrosion, can translate into a sudden bursting of the brake line under hard breaking, leaving you typically with 1/2 of your brakes still working. However, if the operating brakes are just the rear wheels, the braking effectiveness is VERY reduced due to the weight transfer effect onto the front wheels under hard raking. So it could be dangerous.
    (But better than the old 1-loop systems where a burst line would cause COMPLETE 4-wheel brake failure! If the emergency brake just happened to be rusted shut, as mine was, then you are left with downshifting and popping the clutch, which has a limited effect. Fortunately nobody was trying to come though the intersecting road that had the green light as I went flying through he red light. I had the car crushed afterwards.)
     
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  15. ChapmanF

    ChapmanF Senior Member

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    Apparently Toyota thinks it can be difficult to bleed successfully, though.

    There is a procedure in Techstream for air-in-the-head-end bleeding, and that is certainly something I would try if air got in, before giving up.

    But you'll notice, if you read the technician instructions for the D0H recall, that the recall is only intended to replace the accumulator assembly, and if there isn't any sign any nitrogen migrated into the master cylinder, the instructions end there, but if there is, they go on and simply require the tech to replace the M/C as well (new one comes filled with fluid from the factory, I believe).

    So it appears that Toyota is not convinced the M/C can be successfully bled in all cases, or at least when techs are working on the clock, they're better off replacing the whole thing. The D0H instructions do not offer very much explanation for why Toyota thinks this, or whether they expect some cases to be harder and some easier, or how anyone is supposed to tell those cases apart.
     
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  16. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Considering the cost of these components, pretty frustrating: air gets in, throw it away.
     
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  17. Raytheeagle

    Raytheeagle Senior Member

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    For a system that is designed for pressurized liquid, imagine it trying to do the same with air:cool:.

    Something has to give, usually te master cylinder;).
     
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  18. bisco

    bisco cookie crumbler

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    this is certainly the prime suspect. maybe 10 months of drip, drip, drip...not enough to drip onto the floor, but blows off coated parts when driving?
     
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  19. Raytheeagle

    Raytheeagle Senior Member

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    The only thing about brake fluid is that it is corrosive and will eat painted surfaces:cool:.

    If it was seeping, you should see the area where;).
     
  20. rifis

    rifis Junior Member

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    Thanks for that input, bisco. I was wondering about that

    Another question: I was organizing my desk at home tonight - a month's plus worth of bills. I found a notice from Toyota about a "customer support program" - I was about to put it in my paper filing cabinet when I saw the notice showed the warning indicators that might be activated when the "brake booster and brake booster pump assemblies" problem mentioned in the notice did occur. The indicators portrayed are all those that were activated in my car. There is no mention of brake fluid loss in the notice. Can "problem" with "brake booster and brake booster pump assembly" explain a bone dry brake fluid reservoir? I suspect answer is "no". Can someone confirm (or refute) this?

    Thanks, Mendel. I popped the hood via passenger door tonite, and the fluid level has now risen back almost to the level it was at when I first filled it. I then opened drivers door, and it fell a good amount. And I will try to see how the rear wheels free-spin tomorrow; my mph has been down last many months.

    Robert: I wouldn't call our zone high rust; some salt is used in winter on roads.
     
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