3406E Overcooling?

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Chevyho, Dec 18, 2013.

  1. Dec 18, 2013 #1
    Chevyho

    Chevyho Medium Load Member

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    For the past few days my Pete 379 has only heated up to 150F and stayed steady there. I replaced both thermostats with stock ones, and changed both seals. Now the temp holds steady at 175F. The truck seemed to take a long time to get to temp too, I did notice the coolant reservoir was warm already around 100F, should warm coolant be getting there before thermostats open? I did pinch off thermostat vent tube temporarily with no change in temp. I am at a loss here, outside temp is around -20C and i have a winter front on. 175 is bobtailing, havent tried loaded yet with new thermostats. Any help?
     
    Chevyho, Dec 18, 2013
    Chevyho, Dec 18, 2013
    #1
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  3. Dec 18, 2013 #2
    Heavyd

    Heavyd Road Train Member

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    Go to a hardware store and buy one of those infrared temp guns and verify the engine temp compared to the gauge. Measure the coolant temp around the thermostat housing. You may just have a bad gauge.
     
    Heavyd, Dec 18, 2013
    Heavyd, Dec 18, 2013
    #2
  4. Dec 18, 2013 #3
    Chevyho

    Chevyho Medium Load Member

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    I should also add, my engine fan is not on.
     
    Chevyho, Dec 18, 2013
    Chevyho, Dec 18, 2013
    #3
  5. Dec 18, 2013 #4
    Chevyho

    Chevyho Medium Load Member

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    I also suspected the gauge, is it normal for reservoir to be warm before thermostats open though?
     
    Chevyho, Dec 18, 2013
    Chevyho, Dec 18, 2013
    #4
  7. Dec 18, 2013 #5
    Inland-Pilot

    Inland-Pilot Light Load Member

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    reservoir probably warm from water entering via vent
     
    Inland-Pilot, Dec 18, 2013
    Inland-Pilot, Dec 18, 2013
    #5
  8. Dec 18, 2013 #6
    KW Cajun

    KW Cajun Road Train Member

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    Vent valve in radiator cap sounds like it's leaking a bit of coolant thru. Replace the radiator cap.
    The vent valve should allow coolant *into* the radiator, as when engine/radiator cools, but it shouldn't ever allow coolant to go out from radiator to reservoir.
     
    KW Cajun, Dec 18, 2013
    KW Cajun, Dec 18, 2013
    #6
  9. Dec 18, 2013 #7
    puncher

    puncher Medium Load Member

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    I'd sure try the infrared temp gun, they're a must have on the truck anyway, but to me it sounds about right with that cold of outside temp. I bet when you load it it will come close to normal temps, is the heater blowing hot air ?
     
    puncher, Dec 18, 2013
    puncher, Dec 18, 2013
    #7
  10. Dec 18, 2013 #8
    04 LowMax

    04 LowMax Medium Load Member

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    My C15 also typically runs a bit cool, 175 - 185, unless it's on a hard pull. So I am not sure you have a "problem" unless yours wont heat up on a pull.
    I have tried winter fronts, but unless it's minus 30- or colder, they just make the fan come on necessarily. Not sure about the reservoir heat part.
     
    04 LowMax, Dec 18, 2013
    04 LowMax, Dec 18, 2013
    #8
  11. Dec 18, 2013 #9
    Chevyho

    Chevyho Medium Load Member

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    Heater is blowing hot, I think you guys are right ill have to see once it warms up and im loaded. Thanks guys, always helpful.
     
    Chevyho, Dec 18, 2013
    Chevyho, Dec 18, 2013
    #9
    puncher Thanks this.
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