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Thread: heat blows cold at idle but hot when driving

  1. #1

    Join Date
    21 Mar 2005
    Location
    Fort Campbell, KY (Clarksville, TN)

    heat blows cold at idle but hot when driving

    just as the title says. when the car is warmed up and i have the heat on, it blows cold/cool air when its idleing, but HOT when i drive. it seems like the second the car moves it blows hot. any ideas?

  2. #2
    Bender-san
    Sounds like air trapped in the heater core--not much air, though.

  3. #3

    Join Date
    21 Mar 2005
    Location
    Fort Campbell, KY (Clarksville, TN)
    so it shouldnt cause my heat to NOT work at all right?

  4. #4

    Join Date
    12 Oct 2003
    Location
    Missouri
    this happened to my sister's car, and a friendly mechanic walked me through this on the phone.

    1. let the car sit overnight so its completely cold.
    2. take the radiator cap off, and the cap off the radiator resivoir.
    3. start the car and let it sit for 30 minutes.
    4. while its running pour coolant into the resivoir until its ALMOST full, but leave it uncapped. (you want to leave it a little empty because you will have some additional coolant flow into it later.)
    5. still running now CAREFULLY and i do mean with the utmost patience, pour coolant into the radiator in spurts. every so often slowly reach down and squeeze the main radiator hose a few times.
    6. continue pouring coolant until you can squeeze the radiator hose and fluid starts to come up the spout on the top of the radiator.
    7. now turn the car off, cap the radiator and the resivoir and restart the car. 8. let it sit for 10 mins and take her for a spin. should be all good.

    what it is is an air trapped in the block that's preventing the flow of coolant, which im betting you're low on anyway. by doing this while the car is running you are allowing coolant to fill every possible area where air can get trapped, thus forcing the air out of the system (why the caps are off). when u recap everything the system will reset itself noticing that there is a little extra coolant present and will dump it into the overflow resivoir. good luck. let us know if it worked.

    M.

  5. #5
    Bender-san
    Just to let you know: The above MAY work on your particular vehicle...it also MAY not. I know that method doesn't work for beans on most Nissans (the only thing that seems to work on transverse-mount Nissans is lift the front and put the revs to about 3k until you've got 140 degree vent outlet temp). Mind you, every type of car has a different way of bleeding. I've found that what works on one does not necessarily work across the board.

  6. #6

    Join Date
    12 Oct 2003
    Location
    Missouri
    well it works for honda/acuras, mitusubishis, and mazdas for certain. for the purposes of the teg owners on this site im sure itll come in handy.

  7. #7

    Join Date
    21 Mar 2005
    Location
    Fort Campbell, KY (Clarksville, TN)
    well opened the hood this morning... and noticed that the hose that connects between the overflow tank and top of the radiator (by the cap) was snapped off the top of the radiator. There is no way to replace it because it snapped off the nipple thinf it hooks onto too. what should i do? i cant do the above suggested until i reattached this hose.

  8. #8

    Join Date
    12 Oct 2003
    Location
    Missouri
    get urself a razor blade and start workin on gettin the old rubber off, then get urself a new hose from any local autoparts store, or ur local dealer. u should be able to push another hose and a clamp on there.

  9. #9
    stateofbean
    Quote Originally Posted by icemanGSR
    well it works for honda/acuras, mitusubishis, and mazdas for certain. for the purposes of the teg owners on this site im sure itll come in handy.
    A lot of Honda engines also have a bleeder screw where the radiator hose connects to the head.

    But yeah, I've done this plenty of times without using the bleeder, it definately works on Hondas and on Ford V8's. May need to give the lower hose a couple of squeezes too if it's really low on coolant.

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