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Heater Core Mystery ...How is this possible?

Discussion in 'Other Toyota Vehicles' started by Gmillz85, Nov 9, 2020.

  1. Nov 9, 2020 at 8:58 PM
    #1
    Gmillz85

    Gmillz85 [OP] Ski Bum Extraordinaire

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    greg
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    Quick story...
    Did a coolant flush on my 96 Corolla 4afe (1.6l) 5spd manual.

    Now the mystery......

    I'm not getting heat. I'm also not new to this. Here's the real mind bender. Inlet hose to the heater core is cool (not ice cold, but not not hot to the touch) but the outlet hose is piping hot. Wouldn't a blocked heater core cause the opposite? Air bubble?

    Upper and lower rad hoses are hot, outlet hose is hot, car hold's a perfectly steady operating temp and fan comes on when it needs to so I'm ruling out water pump and thermostat.

    Anyone have any experience? I can't understand for the life of me why there would be got coolant flowing out of the heater core but cool coolant or no coolant flowing into it?
     
  2. Nov 9, 2020 at 9:25 PM
    #2
    773_eddie

    773_eddie Trd Pro

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    Was their a reason you did a coolant flush was it working good before the flush?

    Have you made sure that blend door is actually switching from cold to hot?
     
  3. Nov 9, 2020 at 9:41 PM
    #3
    empty_lord

    empty_lord They see me rollin'

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    did you bleed the coolant with the cap off, heater on full blast? those older cars theres a valve that opens the coolant flow. you have to do this or you just get a massive air pocket

    jacking the front of the car up and doing this also helps
     
  4. Nov 10, 2020 at 4:36 AM
    #4
    timsp8

    timsp8 Former Tundra owner for 13 years

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    Usually the heater core is on a side loop and not the main loop so I wouldn’t worry about the thermostat or water pump. That would also explain why the upper and lower hoses are hot. How rough was the flush? It sounds like you possibly pushed some debris in to the door on the heater core and it’s not working properly. I think the exit hose from the heater core getting hot is just coolant backing up from the rest of the system, not passing through the core.
     
  5. Nov 10, 2020 at 5:15 AM
    #5
    Professional Hand Model

    Professional Hand Model A.K.A ‘Golden Hands’

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    Anyway to pop those inlet/outlet hoses off and do a blow through test each way? Confirm flow.
     
  6. Nov 10, 2020 at 5:18 AM
    #6
    Gmillz85

    Gmillz85 [OP] Ski Bum Extraordinaire

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    This was my only thought on why that could have happened making it seem like coolants flowing through. I tried burping the car several times now with the cap off.

    I did a flush cause the system was complete mud, literally 2 inches of sediment I'm my overflow tank. I'm going to flush the heater core when we get some warmer weather again.
     
  7. Nov 10, 2020 at 5:19 AM
    #7
    Gmillz85

    Gmillz85 [OP] Ski Bum Extraordinaire

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    I'll be popping the inlet hose off this morning to check flow, unfortunately I have to wait for the freeze to pass (ya know, colorado winters) to push water through the core. I'll reportback
     
  8. Nov 10, 2020 at 5:53 AM
    #8
    Gmillz85

    Gmillz85 [OP] Ski Bum Extraordinaire

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    No flow coming from the inlet hose whatsoever. I popped the inlet hose off and coolant came flowing out from the heater core side but not through the hose. I assume it was whatever was left in the heater core. I'll have to dicso the inlet hose at the water pump later when I have more time.
     
  9. Nov 11, 2020 at 9:32 AM
    #9
    Gmillz85

    Gmillz85 [OP] Ski Bum Extraordinaire

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    Seems like air bubbles were giving me a hell of a run. I ended up taking the inlet hose off the firewall, stuck a funnel in it and filled until I couldn't anymore. The block ate up a lot of coolant. I'll be doing his one more time but I ended up getting some heat back. I never had a problem burping my system which is why this was so troubling.
     

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