damienk, to pinch off the bypass hose is not to remove it! Literally take a "C-clamp" or "vice-grip" type pliers and "PINCH" the bypass hose to restrict the water "FLOWING" in it. This will force ALL of the water THROUGH the engine and should drop the temp considerably. If not time for a flush, I suggest vinegar first if you do.
Did you check under the fitting at the end of the manifold?
Dave Neptune
