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Thread: Steam coming out of my expansion tank cap hose

  1. #1
    Associate Engineer
    Join Date
    Oct 2012

    Steam coming out of my expansion tank cap hose

    Good day guys, i have observe that a steam is coming out of the expansion tank cap hose. The end of this hose is open to the atmospher so i could see droplets of coolant out of this hose during operation of my liebherr crane. I used to fill coolant in the expansion tank to a correct level. What does it mean to my cooling system? Is it dangerous? The temperature gauge reads 75 deg C. I check the cap and its still good. Im afraid that my gauge is not working good. Pls help.

  2. #2
    Technical Fellow
    Join Date
    Feb 2011
    If vapor is coming out of the hose under any sort of pressure, it suggests to me that you have a head gasket issue and gasses are being forced out of the cyclinder and into the coolant passages.

    The head gasket issue will only get worse as the hot gases burn up more and more of it.

  3. #3
    Project Engineer CCR5600Design's Avatar
    Join Date
    Feb 2011
    Central USA
    I agree with PinkertonD. Coolant in a closed system does not simply disappear. It had to go somewhere. Thus, if you have had to add coolant to the system, it would indicate you have a leak. As you have seen, the leak appears to be in the form of steam. This would indicate a blown head gasket or a crack in the block deck surface or in the cylinder head. It has been my experience that the sooner you fix the problem, the less expensive it is to repair it.


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