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Riddle me this! Turn on the heater, the motor overheats!

Discussion in 'The Hokey Ass Message Board' started by Nataccountguy, Nov 13, 2013.

  1. shooter6
    Joined: Mar 19, 2010
    Posts: 126

    shooter6
    Member

    Sensor close to the return line from the heater core? Maybe its getting the hot water from there while the rest of the water in the system is mixing with cooled water from the radiator.

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  2. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope
    Member

    "The heater is higher than the motor"...That's probably the problem. Vacuum the system to get the air out. I had a GM midsize that did the same thing, the hoses went way down, then back up, and the air couldn't get out. Most GM shops can do the job.
     
  3. 325w
    Joined: Feb 18, 2008
    Posts: 5,291

    325w
    ALLIANCE MEMBER
    from texas

    The heater hose at the manifold should have the heater control valve. You can purge the air by putting a radiator pressure tool in place. Pump to about ten pounds and walk away. The heater control will be needed come summer. Did you hook the Ac ground to the battery as VA recommends. I've heard of strange things happening if that ground is not real good. I've got several new manual heater control valves and the pressure pump. I'm in Hurst Pm if you need to use it.
     
  4. J'st Wandering
    Joined: Jan 28, 2004
    Posts: 1,656

    J'st Wandering
    Member

    That was my thought when I first read it. Is the motor running like a motor that is at 240 to 250 degrees?
     
  5. rockable
    Joined: Dec 21, 2009
    Posts: 2,904

    rockable
    ALLIANCE MEMBER

    This actually happened to me. I could turn on something that drew a lot amps, like the headlights and my temperature would start to climb.....on a cool night. Turns out I did not have a good ground on my gauges.
     
  6. R Pope what your saying I think is Crazy " the Heater is High'er than the Motor"
    That would be all 49-51 Merc Cars the Heater is High'er than the Motor
    so they should run Hot when the Heat is on.!
    I have a 50 Merc with a SBC & I have No Problem with the Heat on

    Just my 3.5 cents
     
  7. I fall in with the electrical issue crowd
     
  8. fsae0607
    Joined: Apr 3, 2012
    Posts: 871

    fsae0607
    Member


    Yeah, if your engine is running this hot you'll know.
     
  9. rockable
    Joined: Dec 21, 2009
    Posts: 2,904

    rockable
    ALLIANCE MEMBER

    First of all, you'd be puking out coolant and having to constantly add more.
     
  10. I have had the same problems with my 51 chevy with Vortec heads I ran a by-pass thinking this would cure the problem. it still did't. I did figure out I mounted the heater core higher than the engine. This made the heater the highest point of the cooling system. I jacked up the front of the car and ran it with the heater on high and the cap off for a few min. bringing the RPM up and down to burp the system. After that it has seem to be OK. You may want to give that a try.
     
  11. 61falcon
    Joined: Jan 1, 2009
    Posts: 772

    61falcon
    Member

  12. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope
    Member

    IHC Loadstar trucks are famous for needing the heater core bled to get water flow because the heater us above the rad cap. Some guys even put in electric pumps to circulate the water. A trick is to drill a 1/8" hole in the heater connection, so that it is covered by the hose. Then with the engine pressured up, work the hose back until the hole is exposed and the air can get out. The rad pressure will blow the air out easily that way.
     
  13. knuc_47
    Joined: May 31, 2013
    Posts: 1

    knuc_47
    Member

    You should read the article in Jan 14's Hot Rod Mag. I had a similar occurrence with my 39 coupe/350 sbc. Fixed/changed the water neck and installed a 180 thermo and drained and installed new antifreeze. Car runs 180 now with no elec fan on.
    I think maybe I met you at a GP funeral viewing a couple months back.
     

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