'94 Sundance overcooling at highway speeds

Discussion in 'General Motoring' started by Sinerviz, Feb 7, 2006.

  1. Sinerviz

    Sinerviz Guest


    I have a 1994 Sundance with 2.5L engine that will not warm up when
    driving at highway speeds. In city driving it will get 3/4 the way up
    the temp guage, but at highway speeds it stays right on cold. Also, in
    city driving, if I really rev the engine high, it will also drop the
    temp. down to cold and then slowly climbs back up.

    I have replaced the Temp. Sender, Temp. Sensor and the thermostat. I
    replaced the thermostat twice, first time with one from Canadian Tire
    which I was told can cause problems, so I bought an OE thermostat and
    nothing has changed.

    I have the manual for this car and the troubleshooting for
    "overcooling" only mentions the thermostat and the temp sender...

    anyone have any ideas what might be going on?

    Sinerviz, Feb 7, 2006
  2. Sinerviz

    maxpower Guest

    Your heater core is stopped up causing the no heat and the temp fluctuation.
    Try and back flush the heater core to see if that helps.

    Glenn Beasley
    Chrysler Tech
    maxpower, Feb 7, 2006
  3. Please clarify: Do you have any evidence the engine is "overcooling" aside
    from the gauge readings? Does your heater grow cold at highway speeds? Do
    you get a Code 17 when you check for flash codes?
    Daniel J. Stern, Feb 7, 2006
  4. Sinerviz

    Sinerviz Guest

    Okay, sorry... yes, other than the guage reading cold, the heater will
    only blow lukewarm air on the highway... when I check for any stored
    codes, I only get 5-5 (end of codes) so the computer doesnt know of any
    problems. I was having a problem with the heater core not giving me
    any heat, but I clamped on a hose to the inlet and outlet (alternating)
    and blew anything out that would come out... when I was done, the water
    coming out was coming out at the same rate as if I had the hose end in
    my hand... When I am driving in the city, there is lots of hot hot air
    coming out of the vents...

    I hope this info helps...

    thanks for the help so far!
    Sinerviz, Feb 8, 2006
  5. Check head gasket. Very common causing those symptoms.
    DAVID PARRILLO, Feb 8, 2006
  6. Sinerviz

    Sinerviz Guest

    Im not sure I understand... what would the head gasket have to do with
    cooling the engine too much? I am not losing any coolant and the
    engine is running good right now... I do not know exactly what is
    involved in checking the head gasket, but if it means taking the engine
    apart, that seems a bit drastic... are there any other suggestions?
    Sinerviz, Feb 8, 2006
  7. Sinerviz

    hartless Guest

    And is your coolant level up? Maybe you have air in the system. If you
    changed the thermostat and temp sensor and such, you have lost some coolant.
    Did you let the ngine warm up with the cap OFF! to let air escape? And top
    up as necessary.
    hartless, Feb 9, 2006
  8. Sinerviz

    hartless Guest

    I should have mentioned I had that problem with a jeep before. Would not
    heat up at all. And the jeep was brand new. Turned out to be a small pinhole
    leak in the rad, which would not build the heat and pressure to warm up
    engine, let alone me when it was -30 in Saskatchewan. A rad cap that is old
    can cause this also.
    hartless, Feb 9, 2006
  9. Sinerviz

    Sinerviz Guest

    Yes, coolant is full and I used the bleeder screw to eliminate all air
    pockets in the system... as previously stated, I am not losing any
    coolant. The coolant gets hot as it should under city driving
    conditions, it is only at highway speeds that it will not heat up...
    Sinerviz, Feb 12, 2006
  10. Is your cooling fan stuck on? Maybe a burned out relay?

    Try pulling the power connection to the cooling fan or fans
    then doing highway driving and see what the temp does. At
    highway speeds the fans shouldn't be powered because
    there should be enough road draft through the radiator to
    cool it, also your not burning a lot of fuel at highway speeds and
    so the engine isn't generating that much heat then.

    Ted Mittelstaedt, Feb 14, 2006
  11. Sinerviz

    hartless Guest

    And what is the outside temperature? And what is your coolant protected to,
    Temperature Wise? If your coolant is too diluted and your on the highway at
    subzero climate then yes your going to be running cooler. And around town it
    will show warm.
    hartless, Feb 18, 2006
  12. None of the above is correct.
    Daniel J. Stern, Feb 18, 2006
  13. Sinerviz

    Sinerviz Guest

    Shoot, there is more information I already knew that I should have
    posted, which would have saved this... The fan actually only comes on
    when the temperature gets about 3/4 the way up the temp. guage. For a
    while I thought it was broken or a signal was getting to it somehow,
    but it did eventually come on. About the car not burning as much fuel
    at highway speed... that does make sense! I never really thought of
    that. The only thing is, could the car REALLY be designed that way? I
    mean, from what I understand, the thermostat should NOT open until the
    engine is very warm, and until it does open, the coolant should just
    keep circulating inside the engine (and through the heater core) until
    its gets quite warm, when the thermostat should open. So to test this
    operation, I tried driving with the heater set to cold (just to make
    sure) and the fan to OFF. It still will not allow the temp. gauge to
    get above the cold level. Is there really enough cold air at 110km/h
    (65mph?) to cool the engine completely, offsetting all the explosions
    happening at 2000-3000 RPM? I am no scientist, but that seems odd to
    think that could be possible... its not like it is -40 outside
    afterall... Actually, the temperature only have to drop to about -5 to
    -10 celcius (25-15 fahrenheit) for this problem to occur. If the
    temperature is above zero, the temp. guage will read warm and I can get
    more heat..

    Is there ANY possible was that some lines could be hooked up wrong that
    would allow the engine to bypass the thermostat and let some coolant
    get through to the radiator? I tried tracing all lines and it really
    seems impossible, but I am at a loss here! There has to be something
    wrong... surely Chrysler couldn't have designed such a poor
    cooling/heating system...
    Sinerviz, Feb 19, 2006
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