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Odd Cooling problem

Discussion in 'Chevy Trucks' started by Arrow, Oct 6, 2004.

  1. Arrow

    Arrow Junior Member
    Messages: 27

    95 1/2 ton Chevy 4x4 350. A few months ago I had to change out my water pump. After I did I noticed that the temp will go from about 190 to 260 then back down to 90 again. all in about 2 minites. I took out the thermostat and the problem went away. I got a new thermonstat and have the same problem. Am I missing something or did i just get 2 bad thermostats. Could it have something to do with the fan clutch? Any other ideas? It does not seem to be getting hot, no motor drag or overheating smell.
  2. Robhollar

    Robhollar Senior Member
    Messages: 766

    It sounds like you have an air bubble in the system. You may have to take it to a shop to get the system blead..Rob
  3. grotecguy

    grotecguy Senior Member
    Messages: 148

    Is the thermostat in backward maybe?? That would cause it to overheat like that.

    Just a thought,
    Mark K
  4. lawnmedic

    lawnmedic Senior Member
    Messages: 703

    It sound like air to me. Your radiator must be completely full with plenty in the over flow container. I fill radiator full then start engine and continue to fill until it starts to warm then cap system and put several inches into the over flow run truck until thermo opens then shut down and let it cool. Then check levels again and repeat if needed...Chuck
  5. streetsurfin'

    streetsurfin' Senior Member
    Messages: 770

    Did the replacement pump have the same size/shape impeller mounted to it as the one you removed? A pump with a higher flow may require a high flow thermostat.
  6. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    does the thermostat you have have a small hole drilled into it to let air/water alwasy sneak buy? I always use robert shaw stuff. Throw the due in a pot of water and crank up the heat with a thermometer there if your unsure of it.
  7. TLS

    TLS PlowSite.com Addict
    Messages: 1,425

    You did get the correct rotation water pump, right?

    Serpentine trucks rotate opposite from v-belt trucks.

    You never know. :confused: