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Why won't my heat work in my 2008

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Drk1524, Feb 13, 2016.

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  1. Drk1524

    Drk1524 New Member

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    Sometimes the heat will work, but not as much now. Which sucks because i live in VT so its alil cold. Except when i'm going 50mph+ then I get some warm air. I just changed the thermostat to see if it was that but no luck. Any advice would be great!!! I was thinking maybe I need to change the water pump, but I'm not sure if that would cause the heat not to work.
     
  2. exstudent

    exstudent Senior Member

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    Did you check the actual radiator prior to changing the thermostat? If NO, there was most likely air in the system, thus the lack of heat.

    Changing the thermostat, introduced even more air into the engine cooling loop, as it seems you did not purge trapped air from the system.

    What coolant did you use? You really should use Toyota SLLC (Super Long Life Coolant).

    If you have more than 100K miles, may be a good idea to change out the water pump, since you already changed the thermostat.

    READ this tread in its entirety! All questions will be answered, as there are useful links within this thread.
    How to replace engine coolant pump and thermostat | PriusChat

    The airlift type coolant tools ($86-$128) make coolant drain&fill easy; no more trapped air due to the vacuum the tool creates. An air compressor is required, if you don't already have one.
    Amazon.com: air lift coolant

    If you don't want to buy the airlift, the Lisle coolant funnel ($25-$30) is a must.
    Amazon.com: lissle coolant funnel
     
  3. andrewclaus

    andrewclaus Active Member

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    In addition to the above, which is definitely the place to start, there may be a fault with an electric pump in the heater loop, that boosts the coolant to the heater core when the engine isn't running. The thread referred to above mentions the Mini VCI diagnostic tool ($25 and an old XP laptop). It's a good tool that gives you testing control on the electric water pumps, reads coolant temp, and makes bleeding much easier. (You can properly bleed the Prius with that and a short length of tubing attached to the upper radiator bleeder valve.)