runs hot at highway speeds

Discussion in 'Troubleshooting & Diagnosis' started by PEGLEG_1, Apr 8, 2012.

  1. PEGLEG_1

    PEGLEG_1 Veteran Member

    175
    0
    Sep 4, 2009
    Huntsville AL
    I have or rather my son has a 78 camaro with a stock crate 350 in it with 350 turbo trans. He was headed up 75 and the temp gauge climbed to about 240 to 250 degrees. He got off at the nearest exit and checked the water level and had to add some. When he took off again the temp dropped down but climbed up again when getting up to speed on the highway. He say the temp is ok driving around town but runs hot out on the highway.

    I was looking for some tips on troubleshooting this.

    first could it be a bad water pump and or the clutch fan is weak?
     
  2. REALZ22equipped

    REALZ22equipped Veteran Member

    123
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    Aug 19, 2010
    hicksville,oh
    sounds like a bad clutch fan. exactly the reason i made the switch to an electric set up
     
  3. dcozzi

    dcozzi Veteran Member

    2,050
    4
    May 1, 2002
    Phoenix, AZ
    There may be adequate airflow at highway speeds even if the fan is crapping out.

    Maybe the motor is leaning out? Plugged fuel line and/or filter(s)?
     
  4. Joekool

    Joekool Veteran Member

    5,736
    0
    Feb 4, 2002
    Hollister CA USA
    A few things that can cause overheating problems at freeway speeds are: colapsing radiator hose, restricted radiator (corrision in the tubes most often), partial stuck t-stat, air in the cooling system, blown head gasket (lets air into the cooling system), also debris in the radiator fins (leaves, dirt etc) can limit airflow, a bad radiator cap that cant hold pressure.

    Basicly you need to look real close at the cooling system and start checking things out.
     
  5. REALZ22equipped

    REALZ22equipped Veteran Member

    123
    0
    Aug 19, 2010
    hicksville,oh
    now that i think about it i had the same problem when my radiator was crapping out. aside from being a small 2 core, it was old. replaced it with a nice aluminum 3 core and ive never overheated again. id say maybe try and flush the radiator first.
     
  6. PEGLEG_1

    PEGLEG_1 Veteran Member

    175
    0
    Sep 4, 2009
    Huntsville AL
    I think I will try a flush first. I never pulled the radiator in that car. It had a good motor no coolant leaks so never touched it.
     
  7. bigblock665

    bigblock665 Veteran Member

    1,053
    0
    Apr 7, 2009
    NY
    try a flush and clean the rad fins of any debris check pump for proper operation at high rpm's. Check your mixture maybe to lean and check timing and make sure its not to far advanced. I seen exhaust glow form mixture and or timing issues. Things may run hotter with the steady rpm highway cruising.
    Good luck!.

    Ps. make sure a hose is not collapsing like the bottom hose... Its supposed to have a steel spring/sleeve... Not sure what its called but its to keep the hose from collapsing.
     
  8. bigblock665

    bigblock665 Veteran Member

    1,053
    0
    Apr 7, 2009
    NY
    Never mind dont touch your timing but id still check to see if you may be running lean.
     
  9. Cardinal

    Cardinal Veteran Member Lifetime Gold Member

    8,166
    0
    Jun 22, 2003
    Endicott, NY
    Have the radiator cap and cooling system pressure checked. THEE most overlooked overheating problem is the radiator cap!
     
  10. bigblock665

    bigblock665 Veteran Member

    1,053
    0
    Apr 7, 2009
    NY
    +1
     

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