Heater not working

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Willl, Jan 23, 2021.

  1. Willl

    Willl Junior Member

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    Just recently got a 2019 LE, but noticed that the cabin heater is not blowing warm/hot air at all, not even on the highest temp setting, the AC is working fine.

    Any suggestions of what I should try check?
     
  2. alanclarkeau

    alanclarkeau Senior Member

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    Cabin filter - but in such a new car it shouldn't be clogged - but who knows? Worth the check.
     
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  3. Willl

    Willl Junior Member

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    Would this cause there to be absolutely no heat coming from the vents at all? No matter how long the car has been running... I'll try to check tomorrow.
     
  4. FuelMiser

    FuelMiser Senior Member

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    Are you running it in AUTO and setting the Temp? If so, Prius waits until it "has heat" before starting the climate control (CC). Maybe it doesn't think the ICE coolant temp is warm enough? Have you tried Manual (setting the fan speed and vent option manually)? Have you tried different positions of the ECO button and/or Front/Rear Bias button? All of these control the operation of the CC.
     
  5. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Under warranty?
     
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  6. Willl

    Willl Junior Member

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    Unfortunately no. 190k miles
     
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  7. ChapmanF

    ChapmanF Senior Member

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    I would start by asking the heater for any diagnostic codes. I'm not sure how that's done in a Gen 4; in Gen 2 and Gen 3, you hold down the AUTO + RECIRC buttons while turning the car on.
     
  8. Elt31987

    Elt31987 Active Member

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    Check the coolant level. Since the heater core is the highest part of the system, if coolant levels are low the hot coolant may not be making it into the heater core.
     
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  9. ChapmanF

    ChapmanF Senior Member

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    Many of the suggestions here are the kind you can use with any car ... even old ones that can't tell you what they think is wrong with themselves.

    In a more modern car, a very sensible first step is "hey, car, what do you think is going on here?"

    Sometimes it won't have anything to tell you, and then you fall back on the generic gumshoe work like in any other car.

    But if it does have something useful to tell you, you just saved a bunch of steps.
     
  10. Willl

    Willl Junior Member

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    I just got the vehicle a few days ago from auction and had not had any chance to look into anything on it so far. There were codes originally but they were cleared and was waiting to see which codes would come back on again. The temp light blinked on a few times but then went off again, finally it triggered a CEL code that was for coolant sensor.

    When I checked the main coolant level the cap was loosely on and the reservoir was completely empty. I bought new coolant and filled it back up to the full line, the CEL went away, drove a few miles and same thing again coolant empty. I did this a few more times, then parked and turned the car on in "maintenance mode" to idle while watching the coolant level. It kept just going down immediately but there was no sign of anything leaking onto the ground.

    I kept filing it up over and over until finally it seemed to stabilize and not go down any more. **Magically the heater also started working again!!**

    I didn't keep driving for fear of something else going wrong so I just went straight back home to swap cars. When I checked the oil it didn't look like there was any issue with coolant mixing so I'm hoping there is not head gasket failure.

    This car has 190k miles on a 2019. There are no codes currently so I'm not sure what I should check. Any advice on service or maintenance that I should have done on it immediately?

    Thanks in advance!
     
  11. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    If coolant level is stabile now you might be out of the woods. 4th gens so far have had no Exhaust Gas Recirculation and head gasket problems.
     
  12. Willl

    Willl Junior Member

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    Unfortunately Toyota dealership diagnostic says needs new engine. Blown head gasket and coolant in 2 of the cylinders.

    Anyone know how much it might be to replace a gen4 motor? The car is a 2019, does it use the same engine as 2016+?

    Is it possible to try to use a head gasket sealer product??? Has anyone had any luck with this before?
     
  13. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    I would heed their head gasket diagnosis, not so sure about replacement engine being the only route; maybe head gasket replacement would suffice*. Did they suspect bent piston rod(s)?

    * Of course going through dealership head gasket repair would likely rival the cost of salvage engine swap.
     
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  14. Willl

    Willl Junior Member

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    Being that it was a diagnostic from World Toyota of Atlanta, I can see them pushing for engine replacement especially since it is a 2019. I wasn't able to get any additional information other than "coolant in 2 cylinders".

    Is there any way for me to assess damage done to the engine at this point?

    Any idea what the cost for an independent mechanic to replace the head gasket might be?
     
  15. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    I’d guess anywhere between $2k and $3k. I think typically a meticulous mechanic would sub the head to a machine shop, for check over, replacement of seals and thorough cleaning. The machine shop may or may not be lumped in with above number, probably $300~500 if not? The full gasket kit from Toyota is around $150~200, and a set of new head bolts around $100~150. Head bolt can theoretically be reused, if still within specs, but replacement is prudent.
     
  16. Elt31987

    Elt31987 Active Member

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    Block Tester BT-500 Combustion Leak Test Kit - Made in USA


    Might be worth using a test kit to test for a blown head gasket. Search Amazon for the above.
     
  17. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    And leakdown test. The Block Tester will check for exhaust gas in coolant IIRC, which is the symptom of one of several ways the head gasket could have been breached. Leak-down test pressurizes a cylinder at TDC of the compression stroke, and determines how much air is escaping, and where.
     
  18. Ramo_958

    Ramo_958 New Member

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    I had similar issue on my 2018 Prius. Warped had gasket around cylinder number 3. Luckily the dealer replaced mine for free and gave me a loaner for a week for free.

    Posted via the PriusChat mobile app.
     
  19. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Interesting, maybe the first 4th gen HG failure posted here? How many miles?
     
  20. Ramo_958

    Ramo_958 New Member

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    Posted via the PriusChat mobile app.
     
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