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Toyota Aqua 2016 Problems & Solutions

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by hassan840, Jun 3, 2023.

  1. hassan840

    hassan840 New Member

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    Hi All,

    I have a Toyota Aqua, S Style Black, Model 2016, Import 2018 & Registered 2019. I will be using this thread to post my questions and look for solutions.
    1. I got this car at about 75,000kms. Now it is at 150,000kms. I am currently using Toyota Petron Plus 10W30 but planning to switch to 5w30. Would it be a wise thing to do at this stage?

    2. What is the transmission oil change interval for this car? I've been reading here and there that it does not require replacement? I am having a hard time accepting that.

    3. I hear a rattle from underneath the car at low revs, probably from the EGR unit as I remember i got the car lifted and tapped on the rectangular unit and it rattled from inside. No check lights, no change in exhaust sound, no drop in mileage etc. What should be done here?
     
  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    This should have zero impact on engine longevity. However you may notice a slight increase in fuel efficiency with the 5W-30. In the USA they tell us to use 0W-20 in these engines, and that gives us even better fuel efficiency.

    That's right, lots of these have run an entire natural car's lifetime on the original trans lube without a problem. This is because the Prius transaxle is fundamentally different from most other auto transmissions: there are no friction parts. No clutches, no bands or drums. The fluid is never pressurized to transmit power, nor is it used as hydraulic media for a valve body or anything.

    So there's no source of particulate contamination, less heat stress and a fundamentally easier job to do. That's why the fluid can last so long.

    It's literally just a few permanently-meshed gears splashing around next to a couple big electric motors inside a metal box. Not much different than a simple differential gear as you'd have in the rear axle of a truck, and those go a long time without oil changes.

    The presence of those electric motors is the special bit- the oil helps keep them cool, and the type of oil is important- you don't want one that could dissolve the coatings on the motor windings, for example. For this reason I suggest using only Toyota WS fluid if you do choose to refresh yours.

    All the EGR stuff is underhood, sort of wrapped around the top of the engine.

    You were probably looking at either the catalytic converter or the exhaust heat recovery system. Those include thin steel heat shields which tend to get rattly as they age and naturally deteriorate from heat, stone chips & weather. They can be tightened, replaced or removed, depending on your circumstances and preference.
     
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  3. hassan840

    hassan840 New Member

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    Appreciate your response. About the last point. Yes you are correct I meant to say the exhaust heat recovery system. The shields are all tight and the rattle comes from inside the rectangular equipment. If i punch it when the car is lifted, i hear metal rattling from the inside. Is that item repairable or should i look for a replacement?
     
  4. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    There is a moving part inside there, a valve that opens and closes to change flow. I don't know if it is repairable or if you need to replace the entire unit.

    I wish you luck!
     
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  5. hassan840

    hassan840 New Member

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    My car's doors do not lock/unlock automatically based on certain criteria defined in the user manual of Prius C. It also shows no customisation option in Techstream. Is it safe to assume that JDM variants (Aqua) are devoid of this capability?
     
  6. hassan840

    hassan840 New Member

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    Hi Guys, i am back with another problem in my Toyota Aqua.

    While driving today, my car started showing ABS/VSC lights and the brake lost all assist power and it became very hard to brake.

    I connected it to Techstream and it shows C1A50 (Brake System Malfunction) and C1391 (Abnormal Leak in Accumulator). I cleared the codes and drove the car and everything appeared to be back to normal. However, the accumulator pump now seems to run for 3-4 seconds after every 15 seconds or so.

    Need guidance on what went wrong and what would be the required corrective action? Does this car (2016 Aqua/Prius C) have separate units for brake accumulator and pump or is it a single unit?
     
  7. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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  8. hassan840

    hassan840 New Member

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    Thanks for responding.

    I hope you can help me understand the issue. My understanding is that the main issue is the abnormal leak in the Accumulator (Part 1) and due to that abnormal leak, another Part 2 (pump?) now has to work more frequently and for longer intervals which will ultimately result in its premature failure.

    What's the exact name for Part 2?

    These JDM cars are imported in my country without any official service/parts available and the routine practice amongst Prius users here has been of replacing both parts sourced from junkyard.

    What if I don't prolong the issue and only replace the Accumulator (Part 1)? Isn't the second part (pump?) still functional and should revert to its original functioning if the abnormal leak is handled?
     
  9. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    [​IMG]

    This diagram shows the two big assemblies of the braking system of the U.S. 3rd generation liftback Prius.

    Not an Aqua/Prius c, but I understand the Aqua has the same two assemblies in the same roles and positions. Not identical parts- they are tuned for vehicle weight, wheel size and (probably) other factors too.

    The upper unit is what does the actual braking work, whether driven by your foot or power assist.

    The lower unit accumulates pressure for future power assist and releases it to the upper unit as commanded. One of those cylindrical cans is an electric pump that stores pressure in the cylinder next to it. That's the motor you hear when you open the door in the morning.

    It is not clear to me whether the leak you are experiencing is within the accumulator, or if it is delivering its pressure appropriately to the upper (booster) assembly and then finding a leak within that unit.

    Sorry I'm not much more help on this, I wish you luck!
     
    #9 Leadfoot J. McCoalroller, Apr 13, 2024
    Last edited: Apr 13, 2024
  10. hassan840

    hassan840 New Member

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    Thanks. That's helpful. Since the code says "Abnormal Leak in Accumulator", i am assuming the culprit is the Accumulator. I was thinking to get only the accumulator replaced first and see if it solves the problem.
     
  11. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    These components have been failing in US 3rd generation cars. It may be worth some time reading those threads. It is worth pointing out that there are at least two common issues surrounding this system, with different consequences and repair actions. Assumptions can be expensive.
     
  12. Sonic_TH

    Sonic_TH Active Member

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    Replace the brake booster assembly, that is where the leak issue is. On my Prius C i replaced the brake pump assembly with a new one, but left the original brake booster, and the leak was still happening. The reason why Toyota recommends replacing both is that, if the car has been running with that issue for a while, the pump is already damaged because of the constant on / off cycle to keep up the pressure.
     
  13. Pri3C

    Pri3C Active Member

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    Edit: Never mind.. was referring to older models.