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Identify this problem please

Discussion in 'The Garage' started by cbbr, Apr 16, 2005.

  1. cbbr

    cbbr 1 ton status GMOTM Winner

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    Truck is overheating at idle. Runs about 210 degrees at 70 mph in 80 degree weather. Theromostat seems to be ok (water feels like it is running). There is a rattling noise (very slight) coming from the fan area. Whats up?
     
  2. sf_wood

    sf_wood Registered Member

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    does it have a clutch fan? check that first.
     
  3. 74757685k5

    74757685k5 1/2 ton status

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    dose it have a fan shroud ? that would make it over heat when not moving.
     
  4. 77K5 / 72k10burb

    77K5 / 72k10burb Newbie

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    Overheating

    You may have a bad clutch fan, no fan shroud, your thermostat may only be opening part of the way, the antifreeze to water mixture may be incorrect, or you may have a small leak in your system causing you not to have the correct coolant level.
     
  5. R72K5

    R72K5 Banned

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    problem wouldnt be fan or shroud with overheating at 80mph
    plenty enough air moves thropugh a radiator at driving speeds to keep it cool, the fan mainly is needed at lower speeds and sitting still

    does it over heat with truck sitting still ?

    does system build pressure and hold it ?
     
  6. cbbr

    cbbr 1 ton status GMOTM Winner

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    Shroud is good. Coolant level is good. Holds presure just fine. Only overheats when standing still. I'm thinking that it is a problem with the fan.
     
  7. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    With the engine OFF....reach in and try to spin the fan blade.

    If the clutch is working properly you should feel resistance and it should not just "spin" freely. If the clutch has failed the fan will "freewheel" even at idle (it's supposed to only disengage the fan from spinning at higher vehicle speeds)

    That would certainly explain overheating at low speeds/idle. :cool1:
     
  8. Mad-Dog

    Mad-Dog 1/2 ton status

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    If it runs 70mph with a water temp of 210F and a ambient air temp of 80F then you may have a worn impeller blade inside the water pump and/or excessive rust buildup in the water jackets.

    I'm surprised the heads have not cracked yet...... :blush:

    Overheating at idle could be the pump/thermostat/fan clutch/shroud...etc

    i run a thermostatically controlled electric fan and a modified thermostat which is just a regular thermostat with the spring and valve removed (restrictor plate or circle track thermostat) :)
     
  9. cbbr

    cbbr 1 ton status GMOTM Winner

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    Fan spins freely. Looks like the clutch is the problem. I'm headed to NAPA once again. Thanks for the help.
     
  10. fourwheelerjeff

    fourwheelerjeff 1/2 ton status Staff Member Moderator

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    let us know the results
     
  11. cbbr

    cbbr 1 ton status GMOTM Winner

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    Replaced the fan clutch. Quick and easy job. The old one was completely shot. Works like a charm now - idled for 30mins in 75 degrees (in the sun, w/ tha A/C on) and stayed cool (180 or so).

    I'm still amazed at the basic stuff that I have to learn. One broken part at a time. Thanks again for the help.
     
  12. sf_wood

    sf_wood Registered Member

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    clutch fan

    Just trying to do my part. A little help can go a long way
     
  13. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    Yes it could. Happened before.
     

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