1994 Ford Explorer 6 cyl Four Wheel Drive Automatic 206000 miles
I have a 1994 Ford Explorer, On Feb. 2nd I replaced the lower intake manafold gasket. When I finished I started the vehicle and about 3-5 min. The oil pressure dropped to 0. I replaced the oil pressure sending unit and it did the same thing after starting the vehicle. Upper engine has very loud knocking noises, like the oil is not getting to the top of the enine. I need to know if the oil pump needs to be replaced or if there is any other problem that I might have overlooked.