Sp4 Expansion Tank Lid Blowing Off

Discussion in 'Technical Help' started by Geekytree, Nov 14, 2021.

  1. Geekytree

    Geekytree New Member

    Sep 26, 2021
    6
    3
    Wales
    My speed four runs ok. Fan comes in/out no problem. Then when I stop, the heat goes up fan cuts in and steam / water come out from under my seat. The only way I stop this happening is to allow the expansion tank level to empty and then I don't have this problem.. Anyone good with coolant system problems with any idea how to solve this one .
     
  2. Linx

    Linx Well-Known Member

    Mar 14, 2020
    198
    93
    Stratford Upon Avon, UK
    It's either a faulty thermostat or a blown head gasket. You can get a sniffer test to check for combustion gasses in the coolant. Maybe check the thermostat in a sauspan on the stove first.
     
  3. capt

    capt Elite Member

    May 8, 2016
    3,050
    750
    western Australia
    There's definitely a fault in there.
    Is coolant old ? Water pump maybe buggered , or as @Linx says head gasket or hopefully only the thermostat.
     
  4. sprintdave

    sprintdave Nurse,he's out of bed again
    Subscriber

    May 25, 2014
    1,533
    750
    Birmingham
    Try changing the rad cap too.
     
  5. Geekytree

    Geekytree New Member

    Sep 26, 2021
    6
    3
    Wales
    Update. Flushed and topped with new but temp went up even when can came on still kept climbing till temp alarm.. took rad cap off and turned it around then the temp came down when the fan came in .I have ridden after and seems ok
     
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