96 350 overheating

Discussion in 'Chevy C/K Truck Forum' started by 96GMCSLE, Mar 1, 2014.

  1. 96GMCSLE

    96GMCSLE Member

    I have a 96 GMC sierra that had a 4.3 vortec but it bent a rod so I did a 5.7 vortec swap. It runs beautifully, really purrs like a new born kitten except the coolant isn't circulating. I put a new thermostat in and it still wont circulate and keeps overheating. But when I undo the top hose on the 5.7 radiator it does come out when the truck is running. Please help!
  2. Scott_Anderson

    Scott_Anderson Rockstar 100 Posts

    Did the 4.3's use the same radiator as the 5.7?
    Sounds like you might need a larger(more cores).
  3. zuki82

    zuki82 Member 1 Year 100 Posts

    sounds like you need a bigger rad.!
  4. 96GMCSLE

    96GMCSLE Member

    It does have a 350 radiator in it but it still wont circulate like the coolant isn't flowing into the motor is staying still. I did replace the water pump
  5. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    If you leave the hose connected, will the rad get hot? The hot water should go from the engine to the rad using the top hose, the cooler water should go back to the engine using the lower hose. Are the hoses hot?

    If the hoses are not hot, the water isn't flowing through the radiator, it must be blocked. Maybe a hose, maybe the t-stat, maybe the rad, but there is a blockage.
  6. 96GMCSLE

    96GMCSLE Member

    My grandpa figured it out. I guess that in some 5.7 swaps air will get into the radiator hoses and create a pocket just like in the brake lines and sure enough just had to bleed the pump and now she runs good. Thank you ones who helped me troubleshooting it

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