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Heating and Cooling

Discussion in 'General Truck Info' started by ktownminihijet, Nov 22, 2009.

  1. ktownminihijet

    ktownminihijet New Member

    So as the title states, I recently got a 92 Hi Jet given to me. I have been going through and slowly doing my own maintenance, I did a rad flush to clear up any debris and build up ect in my system. I pulled thermostat right out and ordered a new one as it wasnt working. I put it back together with thermostat not in it and started the flush. After about 15 mins of idle the upper radiator hose was nice and hot but the lower rad hose was completely cold, also the heater core hoses were stone cold with no heat coming from defrost vents.

    Outside temp was about 5 degrees celcius. What i want to know is where do I go from here in diagnosing lack of cab heat and why the lower rad hose remains completely cold??

    kelowna minihijet
     
  2. MiniBrutes

    MiniBrutes Member

    Air in the system likely. Make sure to bleed it good.

    Most cooling systems do not circulate properly without a thermostat as well. Put your old stat back in for now, unless its actually broken.

    What does the gauge show? High?

    Lower hose should be much cooler than the top hose.
     
  3. ktownminihijet

    ktownminihijet New Member

    f'd

    Ya old thermo is completely screwed, temp guage never got dangerous high, it was in the middle (maybe a bit over the middle)

    What is best way to go about bleeding?
     
  4. MiniBrutes

    MiniBrutes Member

    There should be a bleed screw somewhere around the water neck. (I dont have my info at home here)

    open, fill with coolant until water come out. Close, circulate and again. (

    Another way that is sometimes easier is to lift the front of the truck up a bit. Run the truck with the rad cap off and keep adding coolant. The air ill work its way up to the rad eventually.

    Make sure your heater is set to full heat the whole time, otherwise you will not get any flow through the heater core.
     
  5. ktownminihijet

    ktownminihijet New Member

    bleeding

    As far as I can tell I have bled the air from the system, still havent had the thermostat show up. So with a combination of no thermostat, outside air temp hovering around freezing and a cooling fan that stays on all the time, could this be the culprit as to why my coolant isnt heating up enough to make warm air inside the cab?

    Also what and where do I look for the culprit that keeps my cooling fan on from the time I switch ignition on until I turn it off?

    Sorry for the lack of mechanical understanding, I gotta learn somehow! I am a DIY for life.
     
  6. MiniBrutes

    MiniBrutes Member

    Odd are your thermal switch has failed and a previous owner hotwired the fan.

    There is (or should be) a sensor in the bottom of the rad. It is this sensor that turns the fan on and off. I know when that sensor fails many folks wire the fan right to the ignition or a switch.

    Look at where the wiring goes. If it goes to the sensor, than its probably shot. If it goes elsewhere , its probably hot-wired.

    Another thing you can try is to pull the lines off going to the heater core. This can be done from under the truck. Run a garden hose up to one of the lines and flush it out. See what kind of flow you get through it. It could be plugged.
     

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