I have a little weep appearing from the left hand fixing (I think) bolt (viewed from the front) on the manifold? thingy that the top rad hose (from the right) and the bottom rad hose (from the left) connect to, fitted to the front of the engine. This is where a bleed vent is shown on the BMW TIS diagram. But I don't have a bleeding vent there! Is there a safe coolant additive I can use to seal this little weep, a radweld sort of thing? I'm planning to change the coolant sometime soon. Cheers, Bonzo.