. . . "ine - and plugs onto a nipple on the side of the SERGE TANK - with the engine running - there should be a gentle - constant flow of coolant - from the engine - to the serge tank - if there is no flow - the most likely cause is a blockage in the hollow bolt - follow the hose towards the engine - with the engine OFF - remove the hose - use a straightened metal coat hanger - or something similar - an" .