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Thread: Heater core hose routing

  1. #1
    Sir Procrastinator The man, the myth, the legend Blazer Eagle's Avatar
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    Heater core hose routing

    so after an engine swap from a non-ac blazer to an ac truck...how do i hook these darn heater core lines up?

    the original trucks (ac) motor has two lines from the heater core, one from the radiator and one from the top of the block...im not really srue how they were hooked up

    the new motor has an extra fitting on the water pump, where should all of these hoses run? i believe the heater core leaks because i think it was blocked off...ie capped hose - how should i go about recapping everything? yes i know pictures would help, along with a better description but thatll come tomorow when im awake.....


    as a recap....where the hell do all of my cooling lines go?

  2. #2
    86 350/TH350/208 6" & 39' Senior member Ahays000's Avatar
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    One should go to the top of the water pump and the other to the front of the intake manifold, plug the thermostat housing with pipe plugs... this is my setup without any hoses, but you get the idea.

  3. #3
    Knows their $hit b~lazer's Avatar
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    You should block off the one on the new motors water pump. One of the lines should run to the intake and the other to the radiator. If your not going to hook the heater core up then cap the three holes you have with screw in caps. The one on the radiator might be alittle tricky to cap though. Could just run a hose off of it to the intake and cap the pump?
    Eating hondas and crapping out broncos

  4. #4
    Enjoying Life Chief Hunglikmule 70-K5's Avatar
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    This is how my 70 is run, pretty easy to see what is going on.



    I think that is a plug on the top of the water pump.

  5. #5
    Enjoying Life Chief Hunglikmule 70-K5's Avatar
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    And the 86 is run off the radiator and manifold, all the fittings on the water pump are plugged.


  6. #6
    70.... any reason the hoses are routed differently on the 2 rigs?

    the 86 is correct and the 70 is incorrect..... anyone see why?
    BiggsChevys - KittysKrawlers
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  7. #7
    Sir Procrastinator The man, the myth, the legend Blazer Eagle's Avatar
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    biggs gave me the answer so i cant tell...

    the previous set up after looking at pictures was a hose from the top of the intake to the radiator(to bypass heater core), should i keep this and plug the pump?

  8. #8
    its a matter of personal preference and also depends on what the engine/application wants....

    running from the intake to the radiator causes the engine to warm up slower and run a hair cooler because you will have a thermostat bypass.....

    if the hose is run from the intake to the water pump, it recirculates through the engine allowing the engine to warm up faster and relies on the thermostats operation within the cooling system controlling flow to the radiator....
    BiggsChevys - KittysKrawlers
    1974
    K5 Blazer
    "Beauty"


    454
    TH400
    NP205
    D60/14B
    1974
    K5 Blazer
    "Beastly"


    350
    TH400
    NP203
    D60/14B
    1968
    el Camino


    400
    TH400
    12 Bolt
    1988
    K3500


    TBI350
    TH400
    NP205
    D60/14B
    No, I no longer have any build threads as they were hosted on another site that unfortunately faded away...


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  9. #9
    Enjoying Life Chief Hunglikmule 70-K5's Avatar
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    Quote Originally Posted by Biggs Chevys View Post
    70.... any reason the hoses are routed differently on the 2 rigs?
    Never thought about it I guess... I just repeated how the hoses were in the first place!

    I've been googling trying to get an in/out diagram of all the ports and am coming up blank... Help me label this picture...

    Last edited by 70-K5; 04-28-2011 at 05:01 PM.

  10. #10
    it is not as complicated as one would think, as they dont really have names just intended uses....

    yes manifold port 1 is intended for a heater hose, however you dont have to use a heater....

    port 2 and 3 are intended for temp sensors and senders, like you have with your mechanical temp gauge (can use these to activate an electric fan).... each head should have a port as well (between exhaust ports 1 & 3 - and between 6 & 8 (SB))....

    h20 port 1 and 2 serve the exact same functions, heater hose return.... this keeps the the heater cores coolant circulating through the block...

    from radiator, is the coolant supply source from the radiator.... no names that i know of, as there is no other intended use...

    radiator return is refereed to as the water neck or thermostat housing....

    left and right pump to block ports.... same thing as only a water pump can be mounted there... otherwise the material around the coolant chamber within the block heads and intake are also refereed to as a water jacket...


    as for the heater hose routing, after market fittings and heater cores change things a little, but.... pumping coolant into the lower heater hose port allows the system to purge any air much faster than the feeding the coolant at the top port....
    it is much easier to push air up than down....
    coolant going into the top port can drip/flow past an air pocket in the heater core, this makes for an inefficient heater core.... in some applications people have installed a "purge cap" in the return hose from the heater to the engine because these air pockets can be more of an issue than most people realize....
    BiggsChevys - KittysKrawlers
    1974
    K5 Blazer
    "Beauty"


    454
    TH400
    NP205
    D60/14B
    1974
    K5 Blazer
    "Beastly"


    350
    TH400
    NP203
    D60/14B
    1968
    el Camino


    400
    TH400
    12 Bolt
    1988
    K3500


    TBI350
    TH400
    NP205
    D60/14B
    No, I no longer have any build threads as they were hosted on another site that unfortunately faded away...


    Vote for CK5B!!
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