No Heat After Multiple Tries? Gen2 07

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Mryankovic, Dec 27, 2024 at 10:47 PM.

  1. Mryankovic

    Mryankovic New Member

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    Hello I'm new here, have been driving this car since 2017. Recently replaced the coolant control valve with an aftermarket model and then had the Toyota dealer do a flush and coolant change on the engine coolant system. Everything was just fine for one day and then I lost heat. Since then I have replace the coolant control valve with an oem version and immediately after I added more fluid and left the cap off the radiator to bleed, jumped the CHRS, and let it idle on maintenance mode with the cap off and the bleed screw cracked open. Still nothing. No codes anymore though. Tomorrow I am planning on jacking up the passenger side and trying the process all over again. Not confident that will help. I'm wondering if something got lodged into the heater core after my first day of functioning Heat, but I hear that this is pretty rare on Gen 2s. What else should I do?
     
  2. JC91006

    JC91006 Senior Member

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    You should make sure your hoses are not crossed and connected correctly. It takes a while to properly bleed the coolant. Check a few hours after driving the car and make sure the radiator is full (don't do it when it's hot). You may have to fill the radiator a few times before the coolant level is full. Then check your heat and see if you have heat.
     
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  3. BiomedO1

    BiomedO1 Senior Member

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    Monitor your coolant temperature and check your coolant pump, radiator for cold spots, both upper and lower radiator hoses should get warm warm to hot if circulating properly. Has the thermostat been replaced and how many miles on it?
    If you haven't been changing coolant per OEM specifications, that flush may've knocked something loose and is blocking proper coolant circulation within your system.

    Good Luck.....
     
  4. pasadena_commut

    pasadena_commut Senior Member

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    Review these two videos and make sure you didn't skip any steps:




    I second the suggestion to check the hoses. It is possible to hook them up wrong and take part of the cooling loop out of action.
     
  5. Mryankovic

    Mryankovic New Member

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    Thank you very much. I was wondering about something getting knocked loose as well. All hoses are warm/hot though. Is flushing the heater core if it is clogged a horrible endeavor. And the thermostat is fine as the hoses are warm and it will not overheat even on the highway. Thanks either way.
     
  6. Mryankovic

    Mryankovic New Member

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    I am 99% sure the hoses are correctly reinstalled although I forgot to take a picture before hand. The top hose is the shorter one and the slightly longer one is on the middle, and the large one obviously on the bottom? No white dots on mine as they got wiped away at some point. Thanks for the reply very much appreciated.
     
  7. mr_guy_mann

    mr_guy_mann Senior Member

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    Here's a diagram.

    I assume that if the engine doesn't overheat, then the water pump and drive belt are ok? Is that true?

    If one hose is warm but the second is cooler, then the heater flow is restricted - could be kinked hose, airbound, or clogged core (I don't see cloggs often on Toyotas).

    If both hoses for the heater core are warm but the heater air is cold then something might be wrong with the temperature blend door operation. Screenshot_20230323-084851.jpeg

    Posted via the PriusChat mobile app.
     
  8. Mryankovic

    Mryankovic New Member

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    Again thank you so much for being so accommodating and posting this info, tonight I am going to find out about the heater core by checking the temp of the hoses, I just had the dealership take another look at it because I asked them for some tips and tricks and they said to bring it back in and rebled it for free because they believed they left an air pocket in, but that was not the case, they are suggesting that the heater core may have a clog, which is what I was worried about but again I also have heard that this does not happen too frequently with the Toyotas.

    But yes other than checking the heater core hoses everything else gets up to temperature eventually, the top hose on the coolant control valve is probably the least hot but it is still noticeably warm. Definitely hot coolant inside of it. I'll have to take a look at the temp blend thing tonight if I can get it back from them but I believe it's fine because I can hear it moving.

    Finally has anyone ever done a heater core flush on one of these Gen 2 Priuses? If so what is the easiest method for accessing the hoses enough to connect a garden hose for a flush? Cannot find any videos on it for this car specifically.[/QUOTE]
     
  9. Mryankovic

    Mryankovic New Member

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    What's also strange is that I am poking around right now and it seems like the air coming out of the vents is slightly warmer than outside temperature but only when the engine turns off, as soon as the engine turns on you can feel the vent drop by about 10 degrees

    Just checked heater core lines and it's very clearly warm on the right side and barely lukewarm on the left

    Can I do the garden hose flush on this type of heater core?
     
  10. pasadena_commut

    pasadena_commut Senior Member

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    Did you check the pump that is specifically for the heater? This car has a lot of fluid pumps, there are 3 in the ICE cooling system. I agree that the car would probably overheat if the mechanically driven pump had failed, but I think that only the heat will go out if the little electric pump that moves fluid through the heater core was dead.

    Are you sure that the blend door is working?

    Presumably you can flush the heater core like any other sort of device with a fluid inlet and outlet. However, it might not be a bad idea to post flush it with distilled water before reattaching it to the coolant loop. At least if you have the same sort of incredibly hard water that we do. All those minerals might not play nicely with the Toyota coolant.
     
  11. Mryankovic

    Mryankovic New Member

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    I was hoping to flush the heater core first and then try to replace that heater pump because that was on my radar, I read somewhere else that that was somebody's problem. I'm hoping that I can flush it because you know that's almost a free option, but a genuine pump or even a knockoff is kind of expensive for what the car is worth. I just checked the blend actuator and it definitely moves the little plastic arms around when I change it from cold to hot.

    Unrelated: I've never been on a forum for maintenance advice before and I have to say I just can't believe how nice some people are to take the time to respond and help others, I hardly have the time to ask these questions so it is very much appreciated.
     
  12. pasadena_commut

    pasadena_commut Senior Member

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    Please read this thread if you have not already done so:

    No heat - what's next? | PriusChat

    Regarding the electric pump for the heat. While that is only needed when the ICE motor isn't going (so that the belt driven water pump is inactive) it can still be the problem. If it is clogged with some foreign substance then the coolant cannot get through it. There is some suspicion that cars with the foam rubber bits in the coolant get those from a damaged thermos. The theory being that the thermos has foam between two pieces of metal, but if it is smashed in a wreck while the ICE motor is running the inner metal can be breached, foam breaks off and enters the coolant, and ends up all through the ICE cooling system.

    No heat in cabin, ended up being foam stuck in heater core pump! | PriusChat

    The other possibility is that the car at some point either had a leaky radiator or head gasket, and somebody put stop leak into it. That is a common cause for heater cores to stop working (in general, not just this car.)

    It would be odd though for either the foam rubber bits or stop leaks problems to wait 7 years after you bought the car to show up.

    In this article:

    Mastering the Gen 2 Prius Engine Cooling System - Automotive Tech Info

    they note that the 3 way valve can fail in such a way that there is no heat to the cabin. There are apparently two PIDs, one to set the position and one to read it. So with the proper hardware/software you can test the valve and verify that it is working. Techstream would be the tool most of us would use for this.
     
    #12 pasadena_commut, Dec 31, 2024 at 1:25 AM
    Last edited: Dec 31, 2024 at 1:41 AM