Prius overheating after water pump replacement

Discussion in 'Gen 3 Prius Main Forum' started by michaelbr, Aug 22, 2022.

  1. michaelbr

    michaelbr New Member

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    I asked the mechanic about this and he told me that the tool he has can only detect if the pump is running but cannot tell what RPM the pump is operating.
    The water pump is working but it is not known if the water pump is running at high speed.

    I thought about it, I just don't know how to test.
     
  2. ChapmanF

    ChapmanF Senior Member

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    If he has Toyota Techstream, it has a Data List function under Engine and ECT, where he can see both "Elec Water Pump Target Spd" (how fast the ECM wants the pump to run) and "Elec Water Pump Spd" (how fast the pump is in fact running), and both values are shown in RPM.

    Techstream also allows you to pick a couple values and graph them while driving around, so it would be pretty easy to do that.

    Various other professional-grade scan tools ought to be able to show the same PIDs.

    That would take some improvisational skill—I don't think the repair manual offers any ready-made procedures for it—but it's mostly a tedious matter of buckling down to disconnect various hoses to isolate different parts of the coolant path and apply some repeatable water pressure to see what happens.

    An absolute or severe blockage might be unmistakable, but some less-severe restriction might only show up on comparison to some other, known-working Prius.

    There was a recent thread showing the basic game plan except that the cooling system for the inverter and transaxle was concerned, instead of the one for the engine. In that case, a wayward bolt was found inside one of the hoses, blocking it. (I am hoping that particular explanation stays a rare one.)
     
  3. CR94

    CR94 Senior Member

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    So is it a plumbing issue or a controls (electronics) issue?
     
  4. ChapmanF

    ChapmanF Senior Member

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    That's the present open question, with a few available ways of getting at it.
     
  5. rjparker

    rjparker Tu Humilde Sirviente

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    It seems obvious the car knows there is an overheating issue. It could be as simple as a fuse or bad connector. I would try to figure out why the fans are not running. If they run in ac mode they are obvious good. So they have some king of relay or wiring issue. I would certainly run the ac continuously as a temporary workaround of the fan issue.

    The free or slight fee upgraded "Car Scanner" app with a $30 bluetooth scanner will give you basic data.

    This is a screen I use.
    Car scanner six temps and wps.jpg

    Finally, I would spend $150 for a dealer diagnosis rather than further risking the engine.
     
  6. ChapmanF

    ChapmanF Senior Member

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    Is that screen showing 62.5% control duty for the (engine) water pump, and 3375 RPM for the inverter pump?

    There should be a separate PID for RPM of the engine water pump. Both pumps are variable speed in Gen 3, with essentially the same control scheme, but controlled independently.

    The engine water pump RPM is a PID of the ECM, while the inverter pump RPM is a PID of the power management control ECU.

    Edit: come to think of it, I think the screen is showing both the duty control output and the RPM for the same pump, the inverter pump, and it would be clearer if the control duty label said it was for the inverter pump.

    The reason I think so is that the power management control ECU exposes a PID for its control output to the inverter pump, in units of percent duty cycle.

    The ECM exposes a PID for its control output to the engine water pump, but that one is labeled Elec Water Pump Target Spd, and it is given as a target RPM.
     
    #26 ChapmanF, Sep 10, 2022
    Last edited: Sep 10, 2022
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  7. rjparker

    rjparker Tu Humilde Sirviente

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    There are about 400 Prius data points provided by Car Scanner. The labeling of three user configurable "dashboards" can be edited. The list of points available in this app includes these water pump options:

    C7ECE977-AB6E-43EF-8371-E18231961F7F.jpeg
     
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  8. michaelbr

    michaelbr New Member

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    Very good to know about this, I'm seriously thinking about getting one of these tools for myself, so I can diagnose better before spending money on another water pump without being sure if the water pump is having problems


    I also suspect some clogging, I'll work on that too
     
  9. michaelbr

    michaelbr New Member

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    Good question, my doubt also revolves around these two questions
     
  10. michaelbr

    michaelbr New Member

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    Whenever the car overheats I open the hood and I never see the fans running but in one of the tests with a mechanic I noticed the fan running but very briefly for a short period I never saw them running continuously, only with the A/C switched on.

    The relays were replaced, but I didn't check the wiring.

    I'm thinking of getting a toyota scanner.
     
  11. mr_guy_mann

    mr_guy_mann Senior Member

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    When the car is hot, does the heater put out very hot air from the vents? That would tell you if there is any coolant circulating from the ICE through the heater core.

    Car Scanner gives decent data on a Gen3. You might want to check out the ThinkCar ThinkDiag OBD2 device and app or the XTool Anyscan. Both are pricier than Car Scanner. On a Gen2 I found ThinkDiag is very close to the functionality of Toyota Techstream. Anyscan isn't quite as complete but has codes, data, and bidirectional controls on all systems.

    Either one would let you command the water pump on, watch pump RPM data, etc.

    Posted via the PriusChat mobile app.
     
    #31 mr_guy_mann, Sep 11, 2022
    Last edited: Sep 11, 2022
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  12. michaelbr

    michaelbr New Member

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    On two occasions when the engine was very hot I did a test by turning on the hot air, but the air that was flowing didn't seem to be hot...I need to do more tests to be sure.

    This week I intend to buy a more efficient scanner, I will study which one I buy
     
  13. michaelbr

    michaelbr New Member

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    3E17D852-7BD0-4753-9EBC-74CD276A3358.JPG Yesterday when accelerating my car above 45mph my car turned on all the lights on the dashboard and when I read the error code it showed p0102 (Mass or Volume Air Flow Circuit Low Input) related to the air volume sensor.
    Is there any relationship between this error and overheating?
    Last week I remember the mechanic telling me something and just in case I wrote down what he told me:
    "Oil leaking in the intake system looks like a valve leaking in the air intake"
    Actually I've had an oil leak for some time, and the mechanic told me that I had too much oil in the intake system.
    I read something about a faulty EGR valve can affect the airflow sensor.

    Is there any relationship between this new problem and overheating?
     
  14. rjparker

    rjparker Tu Humilde Sirviente

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    Gen3s always have oil in the intake manifold, primarily from a bad pcv design. The only option for reduction of oil and condensate in the intake manifold is an oil catch can. Unlikely to be a cause of overheating.

    Overheating due to a loss of coolant through the head gasket is common as are clogged passages when someone tries to fix the hg with sealant. Or they have a bad water pump often caused by incompatible coolant or they installed counterfeit "oem" water pumps which fail quickly.
     
    #34 rjparker, Sep 11, 2022
    Last edited: Sep 11, 2022
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  15. michaelbr

    michaelbr New Member

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    The 3 mechanics I took my car to because they couldn't find the cause of the overheating told me it was a blown head gasket, even though the car had overheating as the only symptom.

    The coolant level has always remained the same.
    The exhaust smoke is transparent
    Oil is dark
    Engine starts normally without problems.

    But to clear up my last doubts, I did a chemical test to see if there is combustion residue mixed with the coolant, which is an indication of a problem with the head gasket and the test was negative, there is no combustion residue mixed with the coolant, so I pretty much discard the blown head gasket.
    255AC380-952F-4B99-85FD-1BDFDDDCEF6E.jpeg
     
  16. rjparker

    rjparker Tu Humilde Sirviente

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    If three different mechanics diagnosed a head gasket on a gen3, I would tend to believe them, especially if one or more of them verified water pump operation and used an in cylinder borescope to confirm the head gasket issue.

    Unfortunately the combustion gas check is not always accurate on common gen3 head gasket failures. Especially in the early stages where small leakage into the cylinder only happens after the engine cools and the coolant system maintains pressure. But an occasional severe cold start rattle that some like to blame on the egr is a good indicator. At first the coolant quickly stops seeping as the cylinders start firing. As a failing hg gets worse the traditional combustion gas analyzer may work but those engines are usually blowing white smoke out of the tailpipe and losing coolant fast where its obvious and not just when cold. A borescope inspection as shown below is more definitive in early stages.



    Sometimes a quick fix sealer has been used which temporarily seals the hg leak but clogs up other lines or passages.

    Again, a dealer diagnosis would be money well spent. Otherwise ask your three mechanics HOW they determined it was the head gasket and report back.

    Bonus Tips:
    In the wiring diagram below an experienced tech can easily verify the water pump for 12v power and ground. However the two lines highlighted by the red pointers are a form of pulse width modulation that controls the water pump's speed. These lines are normally inspected with an oscilloscope or advanced graphing meter. Most simply verify movement in the reservoir but if its not there the tech has to move to working from the repair instructions. Similar diagrams exist for the radiator fans.

    3CE9D719-EFC0-49C2-89ED-28946750493E.jpeg
     
    #36 rjparker, Sep 13, 2022
    Last edited: Sep 13, 2022
  17. michaelbr

    michaelbr New Member

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    The problem is that the mechanics only came to this conclusion because they had no alternative, none of them made any kind of measurement that confirmed the problem like the boroscope you mentioned. The coolant in almost a month of problem never went down, still at the same level, quick sealer also never used.
     
  18. michaelbr

    michaelbr New Member

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    After replacing the main parts of the cooling system such as:


    2 Water pump

    2 thermostat

    2 fan relays

    New Coolant

    System air purge

    Temperature sensor

    Coolant reservoir cap



    I always wondered if the problem instead of mechanical is electrical.

    I don't know if it has anything to do with the day the car had the first problem with the water pump I was using a portable vacuum cleaner and the outlet melted after I plugged it into the car's power supply, there was a short circuit, it will be that this caused an electrical problem in the car and affected the system that controls the water pump and fan? I also made the mistake of continually resetting the error codes when the pump was having trouble and even then I drove the car a few miles, did that affect anything? I had also pulled and reconnected a white cable that is in the fuse box and I remember the alarm going off continuously.


    Now I'm getting an air sensor error code P0102 no check engine light, but ABS, brake and traction control light is showing is this normal for this error code? I cleaned the sensor and cleared the code and the lights went out and I drove for over an hour but when I parked and the engine was stalled the reported lights came back

    86A9FA97-1F8A-4D2D-8956-F807A648B9AE.jpeg

    I still think the problem is electrical/electronic, is the system that controls the fan and the water pump having a problem?


    Now I will focus only on this fan problem if I managed to solve the fan problem I believe I can solve the car problem


    Why do the fans never turn on? (only with AC on) Why is it an intermittent fault?


    Could it be a problem with the system that controls the fans?
     
  19. rjparker

    rjparker Tu Humilde Sirviente

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    I don't like the recurring abs lights but they could be false or they could be the common brake booster failure. Brake booster is not going to cause overheating.

    Simple test for the fans. Just leave the ac on which should keep the fans on continuously. A normal cooling system can easily handle the engine and ac even in 105f weather without ever overheating.

    When that fails and it still overheats, spend the next $150 at the dealer and know what the problems really is/are. Then consider options to fix it.

    Yes, it is possible to blow fuses or have a bad ecu. But its not going to run for hours with blown fuses. If you see reservoir movement (verified?) most, if not all, of the water pump electrical is decent.

    It is possible (probable) to get two faulty aftermarket water pumps. We know only OEM water pumps are reliable and even some Amazon or Ebay "oem" pumps are counterfeit. It is possible to install the thermostat wrong.
     
    #39 rjparker, Sep 13, 2022
    Last edited: Sep 13, 2022
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  20. Noahdoge

    Noahdoge Active Member

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    @rjparker Makes a good point. By OEM do you mean the pump with the Toyota logo ground off? Or one from a legit online or local Toyota dealer?
     
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