Dependent upon the make and model of the vehicle, the timing belt and the camshaft sprocket may be removed and the front seal may be replaced if there is leakage of the front seal alone. Start by trying to pry the seal out without any harm to the head, bearing cap or the camshaft, if you cannot do this, buy some half-inch drill and drill a small hole through the seal, then use a self-threading screw to screw several turns into the hole, then take an open-end plier to pull out the seal. If removal is still a problem, loosen the right hand bearing cap so that you remove the faulty oil seal, it is recommended that the old sealant be wiped off before a new one is applied. For Duratec models there is a single large bearing cap for both camshafts because the cap houses the oil passageway and also the solenoid of VCT assembly. Replace the seal housing with a new one and smoothen surfaced that may have caused the seal failure properly through polishing, after this put the bearing with seal onto the seal housing and seal the cap bolts tightly. In fitting a new seal it is best to use a service tool together with a bolt and washer to pull the seal into place when tightening the camshaft bearing cap or a suitable socket can be employed. Lie down some grease to the seal lips for easy fitting, and place the seal over the camshaft end in a manner that it just touches the housing/bearing cap outer periphery. Last, screw the sprocket onto the camshaft with the retention bolt, doing this loosely then, reassemble the remaining parts checking the camshaft position and tightening the timing belt.