Which part of repair manual describes the coolant flow control valve?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by pasadena_commut, Jan 26, 2022.

  1. pasadena_commut

    pasadena_commut Senior Member

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    Trying to locate the part of the service manual which describes the coolant flow control valve, that is, the valve associated with P1121 code. It wasn't in either the engine cooling or A/C sections. Found a couple of versions of TSBs concerning it, and they all just say to "remove coolant control valve" (no reference to a manual/page) after draining the coolant and unhooking the hoses and connector. An early step is to "remove engine under cover LH", which is needed to drain the coolant. Perhaps they mean that the valve should also be removed from below, but it is beyond vague.

    For bonus points, can somebody please explain how air gets out of the thermos? From the manual drawings it looks like both hoses attach at or near the bottom. Is there a tube inside the thermos that extends from one to the top? Something like the dip tube on a water heater, except upside down? Otherwise, I don't see how to push air out of a large volume from the bottom - pushing more coolant in would just compress the air stuck in the top, not displace it.
     
    #1 pasadena_commut, Jan 26, 2022
  2. PriusCamper

    PriusCamper Senior Member

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    I think @SFO has the write up for that... Hope he sees this and shares. I actually have a Prius with that problem and have been procrastinating on dealing with it.
     
    #2 PriusCamper, Jan 26, 2022
  3. ChapmanF

    ChapmanF Senior Member

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    In a way, you're asking a trick question. :)

    I'd have to agree that, in the repair manual (at least an old 2006 pdf of one that has floated around the internet) there isn't any detailed remove/replace procedure I can find. The actual online manuals (more info) do get updated, so it's quite possible a procedure is there.

    Mostly what you can find about it in the repair manual is at P1121 (and at P1120, which the P1121 section says to refer to). There are wiring and plumbing diagrams there and detailed testing steps, but no actual "wrench these bolts in this order to replace the thing".

    The trick part of your question is that the usual answer to "what part of the repair manual describes the part X?" is "not the repair manual, the new car features manual." That's the one that has the descriptions of the different parts and systems and what they're for and how they do it. The repair manual normally just jumps right in and assumes you've already absorbed that.

    That's it exactly. A typical house water heater has both inlet and outlet at the top, but the inlet fitting has a dip tube so the cold water enters the tank at the bottom, and the hot stuff is drawn off the top.

    The thermos is the same way, only the tube is on the outlet fitting and extends up to the top of the tank, so the hot stuff is what is drawn out.
     
    #3 ChapmanF, Jan 26, 2022
  4. pasadena_commut

    pasadena_commut Senior Member

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    By "up to the top" do you mean "really really close to the top"? I figured it would have to be something like that so that the combination of water pumps could push/pull all the air out of the top of the tank. Dip tubes end well above the bottom of a water heater tank, but in this application ending 2 inches (for instance) below the top of the thermos would probably result in an air bubble getting stuck above it.

    The bleeder valve is on the inlet, yes?
     
    #4 pasadena_commut, Jan 26, 2022
  5. ChapmanF

    ChapmanF Senior Member

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    Well, suppose for purposes of argument that there is an inch of air above the top coolant level in the thermos and it never gets circulated out.

    Would you have any reason to notice or care?
     
    #5 ChapmanF, Jan 26, 2022
  6. Elektroingenieur

    Elektroingenieur Senior Member

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    In the Repair Manual (more info) for 2007 Prius cars (RM03Q0U), besides the topics for DTCs P1120/P1122/P1123 and P1121 that @ChapmanF kindly mentioned, removing and installing the water valve with bracket assembly is a step in these procedures:
    • Engine/Hybrid System: P112 Hybrid Vehicle Control: Water Pump with Motor: Removal
    • Engine/Hybrid System: P112 Hybrid Vehicle Control: Water Pump with Motor: Installation
    The water pump mentioned there is part of a different cooling system (for the inverter, MG1, and MG2) than the engine cooling system that uses the water valve. I assume the water valve assembly is just in the way of replacing the pump.
     
    #6 Elektroingenieur, Jan 27, 2022
  7. pasadena_commut

    pasadena_commut Senior Member

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    If it truly never got out, no, that would be fine. However, if the car ever encountered a condition that caused the coolant to slosh around violently in the thermos it could cause the entire bubble to be sucked out of the bottle at once. That might happen on a really bumpy road, or on a panic stop, for instance.

    I used to own a Protege5 which had a condition sort of like that. The oil pan had no baffles, and it was possible on a hard turn for the oil to slosh to one side which reduced engine lubrication. Apparently it was enough to kill a motor (spun bearings) if it was driven hard on turns, but it wasn't enough to cause problems in normal driving.
     
    #7 pasadena_commut, Jan 28, 2022
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