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22 LC Kaw boiling coolant

Discussion in 'Mechanic and Repair' started by brentsawyer, May 21, 2003.

  1. brentsawyer

    brentsawyer LawnSite Senior Member
    Messages: 663

    This is on my Scag TT has about 1000 hours. Recently replaced all gaskets, new thermostat, flushed the radiator but it is still boiling off coolant and runs hot. Usuallly I have to add coolant about every 1-2 hours of operation. What could be causing this. PS there are no leaks. this has been an ongoing problem since last fall but it has just worsened to epic proportions
  2. Nozzleman

    Nozzleman LawnSite Member
    Messages: 225

    Since you say the coolant is boiling I am inclined to guess that you have a bad radiator cap. The coolant system needs to be pressurized to raise the boiling point of the coolant so try a new cap.

    However, did you pressure tested the system to be sure it is not leaking somewhere hidden?

    Also, another possibility could be an air pocket trapped in the system creating a "hot spot".
  3. SWD

    SWD LawnSite Senior Member
    Messages: 988

    The problem is in the cylinder heads on your aluminum motor.
    Those POS engines will warp a head quicker than the IRS can pull an audit.
    Pull both heads and use a known, good, straight edge. Place it across the head over the valves then 90* to that.
    If it isn't perceptually warped, check the valves - are they burn't or undersized, etc.
    If not, the internal webbing on the head has cracked.
    Regardless, they are not worth repairing.
    Buy a new set, with new head gaskets.
    PS - check your compression first - if it isn't 170psi or above you have to correct that problem as well.

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