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Problem with heat

Discussion in 'Gen 2 Prius Technical Discussion' started by Gil Wistrup, Oct 21, 2012.

  1. Gil Wistrup

    Gil Wistrup New Member

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    I have a 2008 Pruis that acts like it has a plugged heater core but I wonder if there is more to it. I thought it had air in the system so I drew the cooling system down with vacuum and was able to get another half quart of coolant in it with a radkit plus vacuum coolant filling tool but it did not change anything. At idle there is no heat until you go up a hill at highway speeds when the heat starts to flow. As soon as the engine slows down or shuts off, there is no heat again. I was going to backflush the heater core but after I noticed all the valves and pumps in the cooling system, I stopped because I wondered if there could be a problem with any of those mechanical parts in the heating system. I don't think that there is still air in the system because the engine temperature is good and the coolant level is full when you remove the radiator cap. With the engine idling, all the hoses in the front of the engine are hot including to the heater storage tank. If you touch the aluminum pipes going into and out of the heater core, one is hot and the other is cold. Has anyone else experienced this problem? Should my next step be to back flush the heater core?
     
  2. nh7o

    nh7o Off grid since 1980

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  3. Britprius

    Britprius Senior Member

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    There is also an electric pump in the heater circuit this should be checked both for supply voltage and operation.
     
  4. Gil Wistrup

    Gil Wistrup New Member

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    I have a Snap On Modis scan tool that has many bi-directional features for this vehicle. I can run the pump with the scan tool. Is there another override that allows you to rev the engine? When I first started attempting to diagnose this problem, I could feel bubbles in the aluminum pipes that go into and out of the heater core. Should I run the pump and rev the engine at the same time? Thanks for your help so far. I will keep you posted.
     
  5. edthefox5

    edthefox5 Senior Member

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    Classic trapped air. Running that pump will not evacuate air. You must give the system a vent to the outside or the air will never escape.

    Air is trapped because the engine cylinder head is higher than the rad. Take off top plastic cover that covers rad cap. Remove cap on rad. Not over flow tank the rad. Jack up front of car as high as possible to get rad higher than cyl head or equal. Run car in inspection mode with heater on. Let run for quite a while. Watch coolant level at rad. When coolant goes down that reflects air is being vented.
    Top off. You may also have to turn on the CHRS coolant heat recovery system bottle as that tends to trap air also.
    Can you do that with the Modis? Very hard car to get air out of system.

     
  6. Gil Wistrup

    Gil Wistrup New Member

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    Is the CHRS the device that looks like a stainless tank in the front of the left fender? If it is, the Modis can run that pump. One would think that they would put a bleeder on top of that tank. Should I run the pump with the engine running? Should I have the engine running faster than an idle or doesn't it matter? Sorry for the stupid questions but this is the first hybrid I have worked on. I will attempt to purge the air out this weekend. Thank you for the help. Gil
     
  7. edthefox5

    edthefox5 Senior Member

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    Yes that's it. Behind and below drivers headlight. That's great the Modis can turn it on. That pump is designed to run briefly so do not run it for an extended time. But that pump is infamous for trapping air after a bleed.
    Do like I said with lifting the car and run it in inspection mode which is a fast fixed idle. Let engine warm up and thermostat opens. Turn on heater but not hot. You want the thermostat to open. Open rad....turn on the CHRS for 10 seconds while car is running. Turn that pump on a few times. If your very lucky you'll see coolant level drop in rad which reflects trapped air is venting out of system. Top off. It should not take long at all once your warmed up and cycling the CHRS.
     
  8. Gil Wistrup

    Gil Wistrup New Member

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    I finally got a chance to attempt to get the air out of the system the other day. I picked the car up so that the front wheels were about three feet off the ground and I let it run in inspection mode for over an hour and it did spit about a cup of coolant out on the floor as it was running. The heat did change from stone cold to moderately tepid as the car idled. When I drove the car, it did give off a little more heat that it did before but it still is no where the way it should be. Do I have to do this process again? It seems really foolish that Toyota didn't put some bleeder screws on the engine or something to get the air out other than running the engine at an angle.
     
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Gil,

    You may be interested in my posts about changing engine coolant here, posts #22 and #42:
    Changing engine coolant | Page 2 | PriusChat

    I suggest that you rev up the engine repeatedly, to help the coolant flow. Also, try squeezing the radiator hoses.

    The cabin air temp should be set to MAX HEAT and the fan speed should be high to promote coolant flow through the cabin heater core. If you hear air bubbling in the cabin heater core then you need to continue the process.
     
  10. epoch_time

    epoch_time Active Member

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    Sounds like the coolant transfeer valve is stuck...
    This is a 3 port valve on the drivers side next to the radiator (on the drivers left of radiator).
    It directs engine head coolant to either thermos storage container or heator core...
    There was a report about a year ago of no heat... he replaced valve on my recommendation and reported sugsess..
    He purchased some sort extended hose clamp removing tool.. but had to drain coolant...and as you might have read
    getting air bubbles out of coolant system is no joy..

    The documented functions of the valve are PREHEAT where heater core is blocked off allowing thermos coolant to only enter
    the ice.
    The next valve function is ENGINE WARM-UP where the valve blocks flow to the thermos bottle and opens flow to the heater core..................................
    The next valve function is DRIVING where flow is both to heater core and thermos bottle.....................
    The next function is POWER-OFF where the thermos bottle route is closed the same as warm-up position.................

    If you drained coolant prior to no heater condition then you should suspect air bubbles .... however if you havent drained coolant
    check into coolant transfeer valve... When bad the dealer can read codes but only dealers code seem to read codes for bad transfeer
    valve..

    There is also an electric heater coolant pump that operates when gas engine stops and heater system is on...

    Hope this helps..
     
  11. Gil Wistrup

    Gil Wistrup New Member

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    I really appreciate everyone's help on this issue.
    Here is the history on the vehicle's no-heat situation.

    The vehicle suddenly lost heat but was never low on coolant. The vehicle was taken to the dealer and they replaced the thermostat which did not solve the problem. The previous owner was told that the car needed a new heater box assembly because one of the air mix doors was broken. They quoted $5500 to repair it because the heater box is only available as an assembly.

    Here is where I have stepped in to try to fix the lack of heat.

    There is no problem with the heater box because you can see through it with a light behind it and watch all of the doors work through their entire range of motion. I thought that the dealer might have introduced air into the system when they replaced the thermostat but I am relatively sure that there is no air in the system. I followed Patrick's instructions to bleed the system (raise the front, run in inspection mode, sqeeeze the hoses, max heat, etc) and I can't hear any gurgling in the heater core. There has never been a temperature issue with the engine either.

    I have a Snap On Modis scan tool that has a fair amount of capability for this vehicle but I did not get any DTCs for the transfer valve. I have access to a Toyota scan tool. Can I output cycle the transfer valve with the Toyota scan tool? The Modis only will run the heater coolant pump.
    Thanks again.
     
  12. shinyyy

    shinyyy New Member

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    I have a 2004 NHW20 second hand PRIUS imported from Japan. The problem is I live in Mongolia, extreme weather condition, -35 to -40 degrees Celsius in the winter. And it's really hard to find a garage in this time of the year in Mongolia, just using a thick car cover which doesn't have any heating or warming system. So I'm worried about two things: 1. Driving without warming up the car. 2. In such cold weather car battery and motor works ok? Want to make car battery and everything of my car last long. Thanks in advance.

    Read more: http://priuschat.com/f/gen-ii-prius-main-forum.22/create-thread#ixzz2ETZg9jsp
     
  13. nh7o

    nh7o Off grid since 1980

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    Suggestions:

    1. If it is possible to fit an engine block heater, you will do much better. For example, the one sold here on PC.
    2. The Traction battery does not work well when very cold. I do not think it is harmed, but the overall performance of the system is reduced. Someone else will have an idea of how much this reduction is. Placing a small heater in the battery compartment will help.
    3. The 12V battery may also not start the car reliably at that temperature. It could use some heat as well.
    4. The electric motors are not harmed by low temperature.
    5. I would be concerned about the touch screen at -40C. Does it work at that temp? Maybe someone knows about that.
     
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  14. shinyyy

    shinyyy New Member

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    Thanks 4 the quick reply. I'll follow your suggestions.
    Everything of NHW20, NHW30 is working excellent at -40 in here. There is no problem with starting my car in the cold morning. But the engine is idle and takes much longer to warm up. As a result fuel consumption increased. (11 liter per 100 km and it was 6 in summer : (
    BTW Gen I, made in 1997 or 98, is as common as muck in Mongolia and... although it's 16 yrs old is still working and running in continental cold climate, gosh! It's wonderful isn't it? Now I'm a huge Prius fan.
     

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  15. cwerdna

    cwerdna Senior Member

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    What's the NHW30?
     
  16. shinyyy

    shinyyy New Member

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  17. cwerdna

    cwerdna Senior Member

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    Seems wrong to me. This is the first I've heard of NHW30.

    There is the ZVW30 which is the Gen 3 (2010+ model year) liftback. Image - Label 050.jpg - Prius Wiki is a picture of the plate.

    トヨタ企業サイト | HVバッテリーリサイクル shows the ZVW30 but no NHW30. http://toyota.jp/prius/003_p_007/spec/spec/index.html also shows ZVW30. (I can't read Japanese.)

    I've got the Gen 2 aka NHW20.

    The next time you see a "NHW30", can you please take a picture of the outside, the interior (dash, shifter and radio area is good enough) and most importantly, the sticker that contains "NHW30"? On US cars, it's visible if you open the driver's door.

    I suspect "NHW30" is a typo that's been propagated.

    There is the NHP10 aka the Prius c/JDM Aqua.
     
  18. shinyyy

    shinyyy New Member

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    Maybe I was wrong. But according to the web sites there is a prius named NHW30. Just check this out frm here. Toyota Prius (NHW30) - Autocade
    also Гибридный автомобиль PRIUS NHW 30 | Экодром
     
  19. nh7o

    nh7o Off grid since 1980

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    That's good to know. Everyone gets worse fuel efficiency in winter, especially if only short trips. The real problem for Prius is high heat, as the traction battery life can be reduced by venting electrolyte. If the car works OK for you, then heating the batteries may not be important.