Report Coolant Leak and Alternator in Engine/Ancilliaries Posted November 19, 2009 The soft aluminium connector pipes bady corode underneath the rubber hoses where they are connected. The corosion expands and starts to lift the rubber hose away from the aluminium tube and water starts to weep from the joint - even when the jubilee clip is tight!. I suggest you remove the rubber hoses from the aluminium tubes and get the tubes out and thoroughly clean the ends with wire brush and emery cloth. You may find the aluminium is so badly pitted that you either need to fill the pits and smooth down (use Belzona molecular metal) or buy replacement aluminium tubes. The neck of the thermostat housing also corodes in the same way and needs checking. I hope that helps.