No heat!!!!!!
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HT4100 4.1, 4.5, 4.9 Discussion, No heat!!!!!! in Cadillac Engine Technical Discussion; Have a 1991 deville 4.9 & recently the heat stopped working! Here's the issue & what i fixed but still ...
  1. #1
    satinblack91's Avatar
    satinblack91 is offline Cadillac Owners Member
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    No heat!!!!!!

    Have a 1991 deville 4.9 & recently the heat stopped working! Here's the issue & what i fixed but still mo heat so please feel free to lend some advice...
    Ok so no heat, i thought it might be my heater core or thermostat?! I flushed my heater core for over an hour, including my radiator with new fluids, and i replaced my thermostat.
    The heat at a stand still or parked is barely luke warn at best but heats up the majority of the time while driving, but it is not as hot as it should be. The vents, blower motor works fine and pushes air fine. I watched a video on line about the loss of heat if there is air in the cooling system.
    My question to that is where if any on my car is there a bleeding valve for the cooling system? Or obviously is there any other thing it could be?
    PLEASE HELP....... Thank you!

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    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    There's a plastic "T" where 3 heater hoses intersect. One of the legs of the T has a restriction built in. If someone replaced it with a standard T, you'll have very little heat. Unfortunately, I don't have a diagram.

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    satinblack91's Avatar
    satinblack91 is offline Cadillac Owners Member
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    Quote Originally Posted by MoistCabbage
    There's a plastic "T" where 3 heater hoses intersect. One of the legs of the T has a restriction built in. If someone replaced it with a standard T, you'll have very little heat. Unfortunately, I don't have a diagram.
    is it by the firewall above the engine? Kinda by the heater core? One of the legs of the T? How would i figure out if it was replaced it with a standard T? What should i do to fix the heat issue bro?

    ----------

    So there is a T with three heater hoses, how would i figure out if it was replaced? And that was already on the car when i bought it and the heater has been running fine until yesterday.

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    MoistCabbage's Avatar
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    Oh, well if this is a new issue, than that's not the problem. IIRC, there's a bleed nipple near the thermostat somewhere.

    If you change the temperature to cold, does the vent temp actually change, or does it seem stuck?

  6. #5
    satinblack91's Avatar
    satinblack91 is offline Cadillac Owners Member
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    I havent checked the temp on cold. I will do that tmrw. I replaced the thermostat, flushed the radiator, heater core, and the only time it heated was when i had the car warmed up and i was driving, but when i came to a stop it got colder.
    I will warm the car up tmrw and try bleeding the valve if i can find it and let you know. Go from there i guess?!? thanks and ill get back to you on what happens tmrw.

  7. #6
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    satinblack91 is offline Cadillac Owners Member
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    Ok so i checked to see if the temp of the air stayed the same when i turned down the temp in the car and it does get cold when i turn it down, but still no heat. And now my coolant temp gauge is on after a few minutes 10-15 running? Never did that before changing the thermostat? Im gonna pull off the thermostat housing tmrw to check it. And let the car run for a while without the radiator cap on hoping it will burp any air pockets out of the coolant lines! ???
    Running out of ideas!!! Any more advice is appreciated.

    ----------

    I checked to see if the temp went colder when i turned down the heater & it did get colder but still didnt heat up. And now my coolant temp gauge is on in the car after 10-15 minutes of running the car. Never did that before i changed the thermostat?!? So tmrw im gonna pull off the housing to check it. Im also going to let the car run for a while without the radiator cap on to see if i can get it to burp any access air in the lines.
    I dont know why the temp gauge is on now.
    Wondering if i didnt let it heat up properly? Seems unlikely since i had it running for 25-30 minutes.
    Im out of options and ideas as of now and would appreciate any advice.

  8. #7
    carnut is offline Cadillac Owners Master
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    Re: No heat!!!!!!

    To properly bleed the air, have the radiator higher than the engine. Either by jacking it up and using jack stands or have it on a steep uphill driveway. Now with the engine cold, remove the pressure cap. Set the climate control temp to 90 degrees. Start the car and with someones help, keep the RPM's up around 15 to 1800. Have a gallon of coolant close by. If there's air, the coolant level will quickly drop after about 4 to 5 min. of running. Quickly add the coolant while keeping the idle high. Once the radiator's full, quickly install the cap. THEN, lower the idle. Top off the recovery tank. Check it next day and add if necc. fluid to the tank.

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    Ranger's Avatar
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    Re: No heat!!!!!!

    Have you checked the vacuum controlled air inlet actuator (#5)?



    Wider view (#12). Also check all the vacuum line connections on #10 (both ends).



    Closer view ($4).


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