1997 peterbilt 379 coolant temperature

Discussion in 'Peterbilt Forum' started by pres1034, Dec 15, 2014.

  1. Dec 15, 2014 #1
    pres1034

    pres1034 Bobtail Member

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    Jul 12, 2011
    atlanta, ga
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    Hey guys, I have a 1997 379, and lately it has been running just fine and suddenly the temperature will go up to about 210-215 and the lights and bells would sound. If i go to neutral and raise the engine, the temp begins to fall immediately and will continue to fall to about 150 degrees. It will do this empty or under a load. It does seem to do it less when I'm climbing grades, or I'm just giving it fuel to pull the load. Sometimes, it will begin to fall back to normal before I have time to do anything. I have a new radiator, 3-month old water pump, clean fins on cac and condenser, new thermostat. Any help would be appreciated. The engine is a Cat 3406e 4758 hp.
     
    pres1034, Dec 15, 2014
    pres1034, Dec 15, 2014
    #1
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  3. Dec 15, 2014 #2
    rodknocker

    rodknocker Road Train Member

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    Dec 18, 2008
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    Sometimes a thermostat will be bad right out of the box. I think 195 degrees is where the temp is normal and 210 is a little high but shouldn't set off any alarms. Cats run hot.
     
    rodknocker, Dec 15, 2014
    rodknocker, Dec 15, 2014
    #2
    baha Thanks this.
  4. Dec 15, 2014 #3
    baha

    baha Road Train Member

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    rodknocker is correct a new thermo. should not let temp go as low as 150, its slow to move and causing prob.
     
    baha, Dec 15, 2014
    baha, Dec 15, 2014
    #3
  5. Dec 15, 2014 #4
    201

    201 Road Train Member

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    high plains colorado
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    I agree on the thermostat too, I've replaced several on my pickup truck, and I think they are all junk. Check the coolant with a separate temp guage, and see how far off the stock one is. It could be an air bubble in the system.
     
    201, Dec 15, 2014
    201, Dec 15, 2014
    #4
  7. Dec 15, 2014 #5
    Flightline

    Flightline Road Train Member

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    Almost There
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    I have the same engine and was told by cat, there is only a 190, 185, and 205 thermostate available thru cat. And have only heard of problems with aftermarket thermostates.
    I would consider changing the engine sensor which is located in the head, just above the thermostate housing.
     
    Flightline, Dec 15, 2014
    Flightline, Dec 15, 2014
    #5
  8. Dec 16, 2014 #6
    Longhood379

    Longhood379 Medium Load Member

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    Nov 30, 2009
    Cremona AB
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    Check the line from the surge tank to the back of the waterpump , if this line gets plugged all kinds of weird crap can happen and it is easier than just ripping the temp regulator out.
     
    Longhood379, Dec 16, 2014
    Longhood379, Dec 16, 2014
    #6
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