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2004 GMC Duramax 6.6 Heat Loss/Pressure in Overflow

Discussion in 'Chevy Trucks' started by BCSCOTT3, Nov 3, 2008.

  1. BCSCOTT3

    BCSCOTT3 Junior Member
    from NY
    Messages: 2

    2004 GMC 2500 Duramax 6.6 Diesel changed 2 thermostats, Heat gets real hot than blows cold, low coolant light comes on. pressure builds up in overflow tank. Cap will blow off it not let out slowly. Is this a head gasket or any other ideas
     
  2. brad96z28

    brad96z28 PlowSite.com Addict
    Messages: 1,526

    It could be or the system could have air in it. Has it been serviced recently drained maybe?
     
  3. MuskokaDon

    MuskokaDon Member
    Messages: 80

    I'd say air-lock or rad cap, you'd know if it was a head gasket
     
  4. BCSCOTT3

    BCSCOTT3 Junior Member
    from NY
    Messages: 2

    AIR LOCK?Whats that and possibly the rad cap
     
  5. MuskokaDon

    MuskokaDon Member
    Messages: 80

    Could be many things...
    is it blowing any smoke?
    if you refill the bottle does it empty out again?
    remove your radiator cap from the jug and start the truck. If coolant flows back out the cap it could be the EGR cooler, it has ruptured internally and coolant is going out the exhaust. The pressure from the exhaust is pushing the coolant back out the rupture and out of the reserve bottle
     
  6. MuskokaDon

    MuskokaDon Member
    Messages: 80

  7. got-h2o

    got-h2o 2000 Club Member
    Messages: 2,439

    Those are symptoms of a head gasket. What else would he know?



    Did this only happen after changing the thermostats? If so, probably air lock. If before, it's quite possibly HGs. Miles? LB7 or LLY? A bad rad cap would cause your top hose to collapse, hg's usually make it build pressure. Bad injector cup sleeves will allow it to blow by through the exhaust.
     
    Last edited: Nov 3, 2008